Mine Safety and Health Administration
Protecting Miners' Safety and Health Since 1978
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U.S. Department of Labor Mine Safety and Health Administration Protecting Miners' Safety and Health Since 1978 |
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[Federal Register: July 16, 2004 (Volume 69, Number 136)] [Proposed Rules] [Page 42811-42840] ----------------------------------------------------------------------- Part II Department of Labor Mine Safety and Health Administration DEPARTMENT OF LABOR Mine Safety and Health Administration 30 CFR Parts 18 and 75 RIN 1219-AB34 High-Voltage Continuous Mining Machines AGENCY: Mine Safety and Health Administration (MSHA), Labor. ACTION: Proposed rule. SUMMARY: The Mine Safety and Health Administration (MSHA/We) are proposing design requirements for approval of high-voltage continuous mining machines operating in face areas of underground mines. We are also proposing to establish new mandatory electrical safety standards for the installation, use, and maintenance of high-voltage continuous mining machines used in underground coal mines. These provisions would enable mines to utilize high-voltage continuous mining machines with enhanced safety protection from fire, explosion, and shock hazards. In addition to providing a mining environment as safe as when using low- and medium-voltage equipment and facilitating the use of advanced equipment designs, the proposed rules would eliminate the need for Petitions for Modification (PFMs) to use high-voltage continuous mining machines. Once promulgated, this rule will supercede existing provisions in granted PFMs. DATES: Comments on the proposed rule must be received by September 14, 2004. Submit written comments on the information collection requirements by September 14, 2004. Public hearing dates and locations are listed in the Public Hearings section below under SUPPLEMENTARY INFORMATION. If individuals or organizations wish to make an oral presentation for the record, we ask that you submit your request at least 5 days prior to the hearing dates. Post-hearing comments and other appropriate data for the record must be received by October 14, 2004. ADDRESSES: You may submit comments, identified by RIN 1219-AB34, by any of the following methods:
FOR FURTHER INFORMATION CONTACT: For information concerning the technical content of the rule, contact Elio L. Checca, General Engineer, Office of Technical Support, MSHA, 1100 Wilson Blvd, Room 2332, Arlington, Virginia 22209-3939. Mr. Checca can be reached at Checca.elio@dol.gov or 202-693-9471 (facsimile). For information concerning the rulemaking process, contact Marvin W. Nichols, Jr., Director, Office of Standards, Regulations, and Variances, MSHA, 1100 Wilson Boulevard, Room 2350, Arlington, Virginia 22209-3939. Mr. Nichols can be reached at Nichols.marvin@dol.gov, 202-693-9440 (telephone), or 202-693-9441 (facsimile). You may obtain copies of the proposed rule and the Preliminary Regulatory Economic Analysis (PREA) in alternative formats by calling 202-693-9440. The alternative formats available are either a large print version of these documents or electronic files that can be sent to you either on a computer disk or as an attachment to an e-mail. The documents also are available on the Internet at http://www.msha.gov/REGSINFO.HTM. We intend to place the public comments on these documents on our Web site shortly after we receive them. SUPPLEMENTARY INFORMATION: I. Public Hearings We will hold four public hearings on the proposed rule. The public hearings will be begin at 9 a.m., and will be held on the following dates and at the locations indicated.
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Date Location Phone
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September 21, 2004........................... Sheraton Birmingham 2101 Richard Arlington (205) 324-5000
Jr., Blvd. North, Birmingham, AL 35203.
September 23, 2004........................... Sheraton Suites Lexington, 2601 Richmond Rd., (859) 268-0060
Lexington, KY 40509.
September 28, 2004........................... Little America Hotel, 500 S. Main Street, Salt (801) 363-6781
Lake City, UT 84101.
September 30, 2004........................... Hyatt Regency Pittsburgh Intl. Airport, 1111 (724) 899-1234
Airport Blvd., Pittsburgh, PA 15231.
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If individuals or organizations wish to make an oral presentation for the record, we ask that you submit your request at least 5 days prior to the hearing dates. However, you do not have to make a written request to speak. Any unallotted time will be made available for persons making same-day requests. The hearings will begin with an opening statement from MSHA, followed by an opportunity for members of the public to make oral presentations to a panel. Speakers will speak in the order that they sign in. At the discretion of the presiding official, the time allocated to speakers for their presentation may be limited. Speakers and other attendees may also present information to the MSHA panel for inclusion in the rulemaking record. The hearings will be conducted in an informal manner. The hearing panel may ask questions of speakers. Although formal rules of evidence or cross examination will not apply, the presiding official may exercise discretion to ensure the orderly progress of the hearing and may exclude irrelevant or unduly repetitious material and questions. A verbatim transcript of the proceedings will be included in the rulemaking record. Copies of this transcript will be available to the public, and can be viewed at http://www.msha.gov. MSHA will accept post-hearing written comments and other appropriate data for the record from any interested party, including those not presenting oral statements, up to 14 days after the last public hearing which is scheduled for September 30, 2004. II. Information Collection Requirements Comments concerning the information collection requirements must be clearly identified as such and sent to both the Office of Management and Budget (OMB) and MSHA as follows: (1) To OMB: All comments may be sent by mail addressed to: Office of Information and Regulatory Affairs, Office of Management and Budget, New Executive Office Building, 725 17th Street, NW, Washington, DC 20503, Attn: Desk Officer for MSHA; and (2) To MSHA: Comments must be clearly identified by RIN Number [1219-AB34] as comments on the information collection requirements and transmitted by e-mail to zzMSHA-Comments@dol.gov, by internet to http://www.regulations.gov, by facsimile to (202) 693-9441, or by regular mail or hand delivery to MSHA, Office of Standards, Regulations, and Variances, 1100 Wilson Blvd., Room 2350, Arlington, Virginia 22209-3939. III. Background A. Events Leading to Regulatory Action The energy used by electrical equipment in mines has increased over the years. Voltage to operate this equipment has also increased to accommodate the increased energy demand. Additionally, high-voltage electric equipment design has become safer than in the past, more efficient, and practical. Because of the industry's need for higher voltages and the marked improvement in the design and manufacturing technology of high-voltage components, we promulgated the ``Electric Motor-Driven Mine Equipment and Accessories and High-Voltage Longwall Equipment Standards for Underground Coal Mines,'' 67 FR 10972 (March 11, 2002) (high-voltage longwall rule). These regulations and standards added a number of approval and safety requirements to Title 30 CFR parts 18 and 75 to accommodate advances in technology for high-voltage longwall equipment. Since we promulgated the high-voltage longwall rule, the mining industry has been moving toward the use of high-voltage continuous mining machines to increase productivity. High-voltage continuous mining machines increase productivity with a minimal increase in machine size. Higher voltages also require less current, resulting in the use of smaller cables. Smaller cables are easier to handle, and can reduce injuries to miners. Existing safety standard 30 CFR 75.1002, Installation of electric equipment and conductors; permissibility, does not allow mines to utilize high-voltage continuous mining machines in or inby the last open crosscut, within 150 feet of pillar workings, or on longwall faces. To allow mines to utilize high-voltage mining machines in the face area of a mine, we grant PFMs. The PFM process allows a mine operator to request modification of a safety standard at a particular mine pursuant to section 101(c) of the Federal Mine Safety and Health Act of 1977 (Mine Act). PFMs may be granted when a mine operator has an alternative method that provides the same measure of safety protection as the existing standard; or when the existing standard would result in diminished safety protection to miners. The PFM process results in safety requirements and procedures that are applicable only to an individual mine. Once a final written decision pertaining to a PFM has been issued, the governing terms and conditions contained in the decision become mandatory for the mine described in the petition. Following issuance of a final decision, we continue to monitor compliance with its terms and conditions. PFMs granted to date for the use of high-voltage continuous mining machines contain requirements for proper installation, electrical and mechanical protection, cable handling, and disconnecting of circuits and equipment. We granted the first PFM for the use of continuous mining machines incorporating onboard high-voltage switching components in 1997. From 1997 through October 2003, we granted 38 PFMs for the use of high-voltage continuous mining machines, and others are being processed. B. PFM Requirements in the Proposed Rule In developing this proposed rule we reviewed the granted PFMs for Sec. 75.1002 to allow the use of high-voltage continuous mining machines. Although the proposed rule includes most requirements that were in the granted PFMs allowing the use of high-voltage continuous mining machines, it does not include all of the requirements. The table below indicates which requirements in the granted petitions are also in the proposed rule. Table 1.--Comparison of Requirements in Granted Petitions for Modification (PFMs) With Requirements in the Proposed Rule
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Number of PFMs including
Requirement in PFMs requirement out of 38 PFMs Requirement included in Proposed Rule
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2,400 Volt limit for continuous mining 38.......................... No.
machine.
120 Volt maximum control voltage......... 38.......................... Yes.
Ground-fault protection.................. 38.......................... Yes.
Short-circuit protection................. 38.......................... Yes.
Look ahead circuit....................... 38.......................... Yes.
Undervoltage protection.................. 38.......................... Yes.
Installation of trailing cables.......... 38.......................... Yes--expanded to allow unused entry.
Trailing cable temporary storage......... 15.......................... Yes.
Guarding................................. 38.......................... Yes.
Guarding locations....................... 38.......................... Yes.
Suspended cables or cable crossovers..... 18 prohibit the use of Yes.
crossovers; 19 permit
crossovers; 1 does not
address the use of
crossovers.
Cable design............................. 38.......................... Yes.
Maximum number of splices................ 37.......................... No.
Prohibiting tape-type splices............ 38.......................... No.
Qualified person to splice............... 38.......................... Yes.
Trailing cable inspection................ 38 for daily inspection; 13 Yes.
for inspection each shift.
Main disconnect device in power center... 38.......................... Yes.
Trailing cable disconnecting devices..... 38.......................... Yes.
Caution labels on HV compartments........ 38.......................... Yes.
Grounding stick for capacitor storage 38.......................... Yes.
devices.
Design, installation, and maintenance of 38.......................... Yes.
disconnecting switches.
Main disconnecting devices and control 38.......................... Yes.
circuit interlocking.
Cover interlocks......................... 38.......................... Yes--two required.
Emergency stop switch.................... 33.......................... Yes.
Barrier and covers....................... 38.......................... Yes.
Troubleshooting and testing limitations.. 38.......................... Yes.
Qualified person......................... 38.......................... Yes.
Ungrounded power circuits................ 38.......................... Yes.
Ground-wire monitor test................. 38.......................... Yes.
Power center lockout and tag procedures.. 38.......................... Yes.
Trailing cable lockout and tag procedures 38.......................... Yes.
Lockout and tagging responsibilities..... 38.......................... Yes.
Ground-fault test........................ 38.......................... Yes.
Grounded-phase detector test............. 37.......................... Yes.
Remove from service if a grounded-phase 38.......................... Yes.
occurs.
Handling trailing cables................. 38.......................... Yes.
Personal protective equipment made 34.......................... Yes.
available by mine operator.
Visual examination of HV insulating 38.......................... Yes.
gloves.
Air testing of gloves.................... 38.......................... Yes.
Voltage testing of gloves................ 38.......................... Yes.
Power sources for tramming............... 15.......................... Yes.
Training................................. 38.......................... No.
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Those requirements in the petitions that were omitted from the proposed rule are as follows: limiting the operating voltage of the continuous mining machine; limiting the number of splices in a high- voltage trailing cable; prohibiting permanent tape-type splices; and training requirements for miners on the high-voltage continuous mining machine systems. The proposed rule does not limit the continuous mining machine voltage, originally specified by the manufacturer to 2,400 volts, because existing regulations in Part 18 allow for approval of equipment up to 4,160 volts. The proposed rule, like the high-voltage longwall rule, has technical provisions to test and evaluate equipment containing on-board switching of high-voltage components up to 4,160 volts. Therefore, we believe that limiting the maximum operating voltage of continuous mining machines to 2,400 volts would unnecessarily restrict the design, and have written the proposed rule to allow for approval of equipment with operating voltages up to 4,160 volts. The proposed rule does not include a limit in the number of splices in a high-voltage trailing cable because we could find no data to support quantifying a maximum number. The design features of the high- voltage cables combined with the sensitive ground-fault protection of the circuit will dictate increased vigilance in the protection and maintenance of the high-voltage cables. Our experience has shown that as a splice is added to a high-voltage trailing cable, leakage current may flow between the phase conductors and the shielding and grounding conductors in the splice. These leakage currents would occur inside the splice, and would not pose a shock hazard to miners. As additional splices are added, the summation of these currents will activate the sensitive ground-fault protection and prevent the continuous mining machine from operating. Additionally, while we prohibited the use of permanent tape-type splices under the petitions, we do not prohibit such use in this proposed rule. Tape-type splices can be used to make an effective splice when proper procedures are followed. Our concern with allowing them had been that the splice materials were often used improperly, and this allowed moisture to enter the splice. Moisture would then degrade the insulation and ultimately create a shock hazard. Instead of prohibiting all tape-type splices, we are proposing that all splices be made with an MSHA-approved splice kit. The approved kits contain materials and instructions on the proper methods for making a splice. The kit includes tape that is self-vulcanizing so it will exclude moisture when applied as instructed, thereby preventing a shock hazard. Finally, the PFMs required certain safety training that is already required by 30 CFR part 48, and, therefore was duplicative. Specifically, all miners who perform maintenance on high-voltage continuous mining machines are to be trained in high-voltage safety, testing, and maintenance procedures. Also, all personnel who work in the proximity of the high-voltage continuous mining machine or who move high-voltage equipment or cables are to be trained in high-voltage safety procedures. These requirements are not incorporated into the proposed rule since they are already required under existing 30 CFR part 48. IV. Discussion of the Proposed Rule A. General Discussion--Part 18 Electric Motor-Driven Mine Equipment and Accessories We are proposing to add specific design requirements for high- voltage continuous mining machines used in face areas and pillar workings of underground mines for manufacturers to follow to obtain our approval. The proposed additional requirements would allow high-voltage switchgear with enhanced safety protection from fire, explosion and shock hazards to be used on high-voltage continuous mining machines. The proposed changes would accomplish several purposes. They would improve the design requirements for continuous mining machines consistent with existing requirements in 30 CFR part 18, accommodate new design technology that is practical, and lessen burdens on the mining community while preserving safety and health protection for miners. The main safety protections addressed in this proposed rule, like the high-voltage longwall rule, are summarized into four areas: (1) Prevention of a high-voltage arc from occurring; (2) prevention of the resulting heat or flame from igniting a methane-air mixture surrounding the machine if an arc or methane explosion occurs within the explosion- proof enclosure; (3) prevention of enclosure failure from an increased pressure rise if an arc or methane explosion occurs within the explosion-proof enclosure; and (4)personal protection for miners from electrical shock hazards when working with or around the high-voltage equipment. This proposed rule addresses only those provisions of 30 CFR part 18 for approval of continuous mining machines with onboard high-voltage switching of high-voltage components. Several of these proposed provisions are either new or derived from existing part 18 requirements. However, we are also proposing a number of requirements identical to existing Sec. 18.53 provisions for longwall mining systems that also apply to high-voltage continuous mining machines. We have chosen to organize the rule so that the requirements for approval of continuous mining machine systems remain separate from those of longwall systems. We invite comments on whether we should reorganize Sec. Sec. 18.53 and 18.54 to combine them or reorganize them in some other way in the final rule. We are proposing this approval rule (30 CFR part 18) in conjunction with mandatory safety standards for high-voltage continuous mining machines (30 CFR part 75). B. General Discussion--Part 75 High-Voltage Continuous Mining Machine Safety Standards We have evaluated the safety of high-voltage continuous mining machines used in underground coal mines for approximately six years. Through the petition process that allows a mine operator to request modification of a safety standard at a particular mine, we have performed specific on-site investigations for all petitions granted for the use of high-voltage continuous mining machines. We have verified that safety concerns of explosion, fire, and shock hazards associated with the use of high-voltage have been sufficiently addressed by advances in the high-voltage technology. For example, we have recognized that high-voltage electric equipment and circuit design improvements in combination with sensitive electrical circuit protections reduce the potential for fire, explosion and shock hazards. We have noted the availability of lighter power cables that reduce back strain and other injury risks to miners often associated with moving, lifting, or hauling the heavier lower voltage cables. Moreover, to our knowledge, there have been no electrical fatalities resulting from using high-voltage equipment under granted petitions. Our evaluation reveals that high-voltage continuous mining machines can be safely used, provided certain conditions are met. Accordingly, we are proposing to revise the existing 30 CFR part 75 electrical safety standards to permit the use of high-voltage continuous mining machines. We have included new safety provisions, as well as almost all the basic provisions from granted petitions relative to the proper installation, electrical and mechanical protection, handling, and procedures for disconnecting circuits and equipment. This proposed rule would not reduce the protection afforded by existing 30 CFR part 75 standards. Rather, it would provide increased protection from electrical, fire, and other hazards. We are proposing revisions to part 75 in conjunction with proposed revisions to 30 CFR part 18 that would address approval requirements for high-voltage continuous mining machines. C. Plain English We have attempted to write this proposed rule and preamble so that it is clear and understandable. In addition to the specific comments we are requesting throughout this preamble including those above concerning proposed Sec. 18.54, we invite comments on how to make the entire rule easier to understand. For example: 1. Have we organized the material to suit your needs? If not, how could the material be better organized? 2. Do we clearly state the requirements in the rule? If not, how could the rule be more clearly stated? 3. Is the technical language clear? If not, what language requires clarification? 4. Would a different format (grouping or order of sections, use of headings, paragraphing) make the rule easier to understand? If so, what changes to the format would make the rule easier to understand? D. Section-by-Section Discussion Part 18 Electric Motor-Driven Mine Equipment and Accessories Section 18.54 High-Voltage Continuous Mining Machines (a) Separation of High-Voltage Components From Lower Voltage Components Proposed paragraph (a) of this section was derived from existing Sec. 18.53(a). The existing requirements for high-voltage longwall equipment are contained in Sec. 18.53, High-voltage longwall mining systems. It would require separation of low- and medium-voltage circuits from those with high-voltage circuits in each motor-starter enclosure, by separate compartments, barriers, or partitions. Barriers and partitions, under this proposed rule, like the high-voltage longwall rule, would have to be constructed of grounded metal or nonconductive insulating board. When designing the barriers or partitions, consideration should be given to possible effects of pressure-piling within the enclosure due to restricted configurations within enclosures. Such restrictions can cause an accelerated rate of burning of a methane-air mixture that can create abnormal pressures within the enclosure. This extreme pressure can cause the enclosure to fail and possibly ignite methane gas or coal dust surrounding the enclosure, thereby putting miners at risk. The proper design of enclosures, including placement of barriers and partitions can limit the damaging effects from pressure piling. Under this proposed rule, barriers, partitions, or separate compartments must be provided between high-voltage and lower-voltage compartments to protect persons from coming into contact with energized high-voltage conductors or parts such as when testing and troubleshooting low- and medium-voltage circuits on the continuous mining machine. (b) Interlock Switches Proposed paragraph (b) of Sec. 18.54 would require covers or removable barriers or partitions of motor-starter enclosure compartment(s) containing high-voltage components to be provided with at least 2 interlock switches. Proposed paragraph (b) is derived from existing Sec. 18.53(b) with the addition of the word ``removable'' to clarify that interlock switches would not be required on permanently installed barriers, or partitions. Interlock switches protect miners entering enclosures from shock hazards by de-energizing high-voltage circuits when these barriers, partitions, or covers are removed. Like the high-voltage longwall rule, a minimum of two interlock switches per cover would be required and must be wired into the circuitry so that operating either switch would de-energize the incoming high-voltage circuits to that enclosure. (c) Circuit-Interrupting Devices Proposed paragraph (c) of Sec. 18.54 is derived from the requirements in the granted PFMs for the use of high-voltage continuous mining machines and is identical to Sec. 18.53(c). It would require that circuit-interrupting devices be designed and installed to prevent automatic reclosure. This provision would protect against shock, fire, and explosion hazards. For example, if a roof fall or equipment insulation failurewere to result in a short-circuit or ground-fault condition, the automatic reclosing of circuit-interrupting devices would re-energize the circuit and could create a hazard to miners. (d) Transformers Supplying Control Voltages Proposed paragraph (d) is primarily derived from existing Sec. 18.53(d), but incorporates changes based on our experience in enforcing that provision. The proposed changes would clarify the grounding requirements of the electrostatic shield for various transformer designs. Proposed paragraph (d)(1) of this section would require that the nominal control voltage of alternating-current circuits not exceed 120 volts line-to-line. This requirement would allow any appropriate control circuit wiring configuration of 120 volts line-to-line or less to exist, and would be consistent with the high-voltage longwall rule and granted petitions for high-voltage continuous mining machines. Limiting the control voltages to 120 volt, line-to-line will reduce the potential for electrocution hazards to miners. Proposed paragraph (d)(2) specifies that control transformers with high-voltage primary windings that are located in each high-voltage motor-starter enclosure or that supply control power to multiple motor- starter enclosures, have an electrostatic (Faraday) shield installed between the primary and secondary windings. After the high-voltage longwall rule was promulgated, we became aware of the different control transformer designs which affect how electrostatic shields are grounded. Proposed paragraphs (d)(2)(i) and (ii) address those different grounding methods. The purpose of the electrostatic shields is to provide isolation between the high-voltage and lower-voltage circuit(s). This isolation would protect miners against high-voltage shock hazards should a fault develop between the primary and secondary windings. Electrostatic shielding would also prevent transients (sudden short term changes in voltage and current) occurring on the primary circuit from being transferred to the secondary circuit. Such transients could cause premature damage to electrical and electronic control equipment and create an economic burden for the mining industry. Grounding of the electrostatic shield would be dependent on the design of the transformer. If a transformer is designed with an external grounding terminal, proposed paragraph (d)(2)(i) would require the shield to be connected to the equipment ground by a minimum of a No. 12 American Wire Gauge (A.W.G.) grounding conductor extending from the external grounding terminal. This minimum wire size requirement is intended to ensure proper current carrying capacity and mechanical strength of the grounding conductor. Proposed paragraph (d)(2)(ii) would require that if the transformer is designed without an external terminal, the electrostatic shield would have to be connected to the transformer frame by an internal conductor. This conductor, installed when the transformer was manufactured, would be considered an extension of the shield, and therefore, could be smaller than a No. 12 A.W.G. In this case, bolting of the transformer frame to the equipment enclosure would provide the required path to ground, as long as an effective low impedance electrical connection is maintained. (e) Onboard Ungrounded, Three-Phase Power Circuit The provisions of proposed paragraph (e) of this section are derived from the granted PFMs for the use of high-voltage continuous mining machines. Proposed paragraph (e) would require a grounded-phase indicator light when three-phase, ungrounded power circuits are used onboard the continuous mining machine. These circuits include high- voltage transformers on-board the machine to power low- and medium- voltage circuits. The secondary windings of these transformers are connected in an ungrounded configuration. The purpose of requiring an indicator light would be to detect or alert the operator to grounded- phase conditions in the ungrounded circuits. With ungrounded systems, the capacitive coupling between each phase conductor and ground can subject the ungrounded system to dangerous overvoltages resulting from intermittent ground faults. The occurrence of a second grounded-phase would create a short-circuit and possible arcing between components. This could result in a methane-air explosion that could result in catastrophic failure of the enclosure or cause a shock hazard to miners. Therefore, it is important to detect and immediately correct any grounded-phase condition to prevent a hazard. Paragraphs (e)(1) through (e)(3) address these concerns. Proposed paragraph (e)(1) would require an on-board grounded-phase indicator light to alert the machine operator if a grounded-phase condition were to occur on any ungrounded, three-phase power circuit. Proposed paragraph (e)(2) would require the indicator light to be installed so that the machine operator could readily observe it from any location where the continuous mining machine is normally operated. Proposed paragraph (e)(3) would require that the onboard ungrounded, three-phase power circuit contain a test circuit to verify the integrity and proper operation of the grounded-phase detection circuit. Also, the test circuit must be designed so that (1) the designated person would not have to remove the electrical enclosure covers to activate it; and (2) it would not create a double-phase-to- ground fault resulting in a short-circuit condition. We note that such a design already exists, as we have seen equipment where a readily accessible test switch was used to activate the test circuit and not require the removal of electric enclosure covers. This design would minimize hazards to personnel by making the test easier to use and avoid placing personnel in close proximity to exposed, energized conductors, thereby minimizing the potential for shock hazards. (f) High-Voltage Trailing Cable(s) Proposed paragraph (f) would address high-voltage trailing cables, and is derived from: the granted PFMs for the use of high-voltage continuous mining machines; proposed Sec. 75.826; existing Sec. Sec. 18.35 and 18.47; and Insulated Cable Engineer's Standards (ICEA)S-75- 381/National Electrical Manufacturer's Association (NEMA) Standard NEMA WC 58-1997. The proposed rule incorporates by reference the current carrying capacity (ampacity) ratings and outside diameter requirements for trailing cables listed in the ICEA/NEMA Standard. This requirement would standardize the ampacity and outer diameter of cables to prevent overheating and ensure the interchangeability of trailing cables provided by different manufacturers. In accordance with the requirements for incorporating by reference, proposed paragraph (f) details how the public may inspect or purchase a copy of the incorporated standard and notes that according to his/her statutory authorization, the Director of the Federal Register has approved the incorporation by reference. Existing Sec. 18.35 contains general requirements, such as minimum conductor size, maximum cable length, flame resistance, etc., for trailing cables. Existing Sec. 18.47(d)(5) addressing voltage limitations of trailing cables requires cables to include grounding conductors, a ground check conductor, and grounded metallic shields around each power conductor. Proposed paragraphs (f)(1), (f)(2), (f)(3), and (f)(4) would specify requirements applicable to trailing cables for high- voltage continuous mining machines. Specifically, proposed paragraph (f)(1) would require trailing cables to be constructed to include 100 percent semi-conductive tape shielding over each insulated power conductor. Proposed paragraph (f)(2) would require a grounded metallic braid shielding over each power conductor. The 100 percent semi-conductive tape shielding material and grounded metallic shield around each power conductor would protect miners from shock and electrocution hazards. Also, the combination of the tape and shielding requirements would prevent voltage stresses on the conductor insulation. The shielding maintains a symmetrical distribution of voltage stresses. This is critical at higher operating voltages. Shielding also prevents transients on power systems and reduces the hazard of electric shocks. Proposed paragraph (f)(3) of this section would require that the cable include either a ground check conductor not smaller than a No. 10 A.W.G. or a center ground-check conductor not smaller than a No. 16 A.W.G. stranded conductor. Cables designed with a center ground-check conductor do not need to have the size of the ground-check conductor as large as a ground-check conductor located on an interstice of the cable since the conductor would be exposed to less mechanical stress and damage. Therefore, a No. 16 A.W.G. ground-check conductor would be adequate. Such designs have been used in high-voltage longwall applications for several years, and are currently permitted under existing Sec. 75.822. Proposed paragraph (f)(4) of this section is based on language contained in granted PFMs for the use of high-voltage continuous mining machines. It would require the use of two reinforced layers of jacket material. Under this construction, the inner-most layer of two-layered protective cable jacket would be required to be a color distinctive from the outer jacket color. This requirement would also complement the inspections required in proposed Sec. 75.832(d) since the purpose would be to allow for easy recognition of damage to the jacket. The provision would not permit the color black to be used for either layer since it would be hard to identify damaged areas. (g) Safeguards Against Corona Proposed paragraph (g) of Sec. 18.54 is identical to existing Sec. 18.53(k). Proposed paragraph (g) would require a manufacturer to provide safeguards against corona on all 4,160 volt circuits in explosion-proof enclosures. Corona is a luminous discharge that occurs around electric conductors that are subject to high electric stresses. Corona can cause premature breakdown of insulating materials in explosion-proof enclosures onboard the high-voltage continuous mining machine. This could result in arcing and possibly create an explosion hazard. Although corona usually does not present a hazard until a voltage of 8kV is reached, safeguards should be taken at 4,160 volts. Safeguards would include using cables with a corona resistant insulation such as ethylene propylene to avoid small nicks or cuts in the cable insulation and to minimize high-voltage transients. As with the high-voltage longwall rule, this provision is not intended to require stress cones or similar termination schemes to prevent corona. (h) Explosion-Proof Enclosure Design Proposed paragraph (h) of this section is identical to existing Sec. 18.53(l). It would require limiting the maximum explosion pressure rise within an enclosure to 0.83 times the design pressure for any explosion-proof enclosure containing high-voltage switchgear. This requirement would protect against explosion hazards that may arise from the effects of a sustained high-voltage arcing fault. Arcing faults may significantly contribute to a pressure rise in an explosion-proof enclosure during an internal methane-air explosion. A pressure rise above the design limit of the enclosure could cause the explosion-proof enclosure to fail to contain the methane explosion. (i) Location of High-Voltage Electrical Components Near Flamepaths Proposed paragraph (i) is identical to existing Sec. 18.53(m). It would require that high-voltage electrical components located in high- voltage explosion-proof enclosures not be coplanar with a single-plane flame-arresting path. This protective measure would prevent the heat or flame (from an arc or methane explosion in an explosion-proof enclosure) from igniting a methane-air mixture surrounding the enclosure. This requirement would prevent the possibility of conductor material particles from being expelled from the enclosure through the flame-arresting path. Particles of molten material are emitted from the conductors whenever an arcing short-circuit occurs in an explosion- proof enclosure. Expulsion of these particles from the enclosure can occur if their source is in the same plane as the flame-arresting path and a pressure rise coincides with the short circuit. Once these particles are expelled from the explosion-proof enclosure, they can ignite an explosive atmosphere should one be present. This possibility would not arise with multi-plane flame-arresting path surfaces because a deflection in the path would prevent ignitions by expelled particles. (j) Minimum Creepage Distances Proposed paragraph (j) of Sec. 18.54, including the table for minimum creepage distances, is identical to existing Sec. 18.53(n). Proposed paragraph (j) would require that rigid insulation between high-voltage terminals or between high-voltage terminals and ground be designed with creepage distances in accordance with the minimum creepage distance table proposed in this section. The minimum creepage distances specified would provide adequate insulation to prevent a phase-to-phase or phase-to-ground fault that could cause a possible explosion. The required creepage distances are determined based upon the phase-to-phase use voltage and the Comparative Tracking Index (CTI) of the insulation to be used. An appropriate method of determining the CTI of the electrical insulating material is described in the American Society for Testing and Materials Standard, ASTM D3638 ``Standard Test Method for Comparative Tracking Index of Electrical Insulating Materials.'' The MSHA derived creepage distances in the table are consistent with most commercially available high-voltage components to which this provision would apply. (k) Minimum Free Distances Proposed paragraph (k) of Sec. 18.54, including the table discussing Minimum Free Distances (MFDs), is identical to existing Sec. 18.53(o). It would address a requirement for MFDs within an explosion-proof motor-starter enclosure. During development of the high-voltage longwall rule, we determined that if phase-to-phase arcing occurred, there might be sufficient arc energy to heat the walls of the enclosure beyond the safe design temperature. This could cause failure of the enclosure and create an explosion hazard if the MFDs are below what is specified in the table. Consequently, distances between the wall or cover of an enclosure and uninsulated electrical conductors inside the enclosure were established to prevent wall or cover damage that may result from phase-to-phase arcing. Under proposed paragraph (k)(1), we would allow for values not specified in the MFD table provided they meet the specific engineering formulas on which the table is based. These formulas are adopted from existing Sec. 18.53. Under proposed paragraph (k)(2), we would require the minimum free distance values in the table or those values calculated using the prescribed formula to be increased by an incremental amount based on the system voltage. The minimum free distance must be increased by 1.5 inches for 4160 volt systems and by 0.7 inches for 2400 volt systems when the adjacent wall area is at the top of the enclosure. This increase in distance is necessary to account for the thermal effects caused from the arc, due to heat rising within the enclosure. Under this proposed paragraph we would also consider the use of steel shields in conjunction with an aluminum wall or cover. Under these circumstances, the thickness of the steel shield would be used to determine the minimum free distance. Additionally, we would consider the use of alternate techniques and methods, as permitted by Sec. 18.47(d)(6), that preclude the possibility of high-energy arcs that would heat the walls of explosion- proof enclosures beyond safe temperatures. If upon evaluation, equivalent safety were demonstrated, we would accept these technological advances and the results of additional research in this area. (l) Static Pressure Testing of Explosion-Proof Enclosures Containing High-Voltage Switchgear Proposed paragraph (l) of this section is derived from existing Sec. 18.53(p). Proposed paragraph (l)(1) would require that prior to performing explosion tests required under existing Sec. 18.62, the manufacturer must perform a static pressure test as detailed in proposed paragraph (l)(1)(i) on each prototype design of explosion- proof enclosure housing high-voltage switchgear and the enclosure meet acceptable performance criteria as specified in proposed paragraph (l)(1)(ii). Proposed paragraph (l)(1)(i) describes the prototype static test procedure and specifies that the enclosure be internally pressurized to a pressure no less than the design pressure, with the pressure maintained for a minimum of 10 seconds. The pressure is then released and the pressurizing agent removed from the enclosure. We have developed the static pressure test with its acceptable performance criteria to ensure each enclosure design would be capable of withstanding its design pressure. By requiring static pressure testing on each prototype enclosure, we believe that the adequacy of enclosure design would be verified. Proposed paragraph (l)(1)(ii) specifies the acceptable performance criteria that enclosures undergoing the prototype static pressure test must satisfy. Acceptable performance would be achieved if the enclosure, during pressurization, did not result in the rupture of any part that would affect the integrity of the explosion-proof enclosure or cause leakage through welds or castings. Further, the provision would require that following removal of the pressurizing agents, the enclosure would not exhibit visible cracks in welds, permanent deformation exceeding 0.040 inches per linear foot; or excessive clearances along flame-arresting paths following retightening of fastenings, as necessary. Any of these conditions would constitute unacceptable performance because they would indicate that the explosion-proof integrity of the enclosure has been compromised. Proposed paragraph (l)(2) would require the manufacturer of every explosion-proof enclosure housing high-voltage switchgear to either conduct the static pressure test for each manufactured unit or follow an MSHA-accepted quality assurance procedure covering the inspection of the enclosure. These procedures are typically required by nationally recognized quality systems certification organizations. The purpose of the quality assurance procedures would be to verify that the manufactured enclosure meets the design specifications of the original enclosure tested. Part 75--Mandatory Safety Standards--Underground Coal Mines Section 75.823 Scope Proposed Sec. 75.823 describes the scope of this proposed rule. Proposed Sec. Sec. 75.824 through 75.833 are electrical standards that would apply only to the use of high-voltage continuous mining machines. Proposed Sec. 75.823 also specifies that under this rule a ``qualified person'' means a person qualified under existing Sec. 75.153; Electrical work; qualified person. This requirement is derived from existing Sec. 75.820(a), and is included in the scope to prevent repetition of this requirement. Consequently, any reference in this proposed rule to electrical work on circuits and equipment associated with high-voltage continuous mining machines would need to be performed by persons qualified in accordance with Sec. 75.153. This electrical work includes all circuits and equipment, not just high-voltage. Also, this proposed rule is similar to the high-voltage longwall rule in that non-qualified persons working under the direct supervision of a qualified person would not be permitted to do electrical work, even when directly supervised by a qualified person. We believe that when a person is qualified to perform electrical work on low-, medium-, and high-voltage circuits, he is able to identify hazards and follow safe work procedures. Therefore, only qualified persons would be permitted to work on circuits associated with high-voltage continuous mining machines. This requirement is intended to prevent electrical accidents. Other standards in 30 CFR would also apply to this equipment, where appropriate. For example, safety standards, such as grounding and ground-monitor requirements contained in subparts H and I of part 75 that are currently applicable to high-voltage installations are also applicable to high-voltage continuous mining machines. However, Sec. Sec. 75.813 through 75.822 apply only to high-voltage longwalls. Additionally, once promulgated, this rule will supercede existing provisions from granted PFMs. Section 75.824 Electrical Protection Proposed Sec. 75.824, with the exception of paragraph (a)(2)(ii), is derived from the granted PFMs for the use of high-voltage continuous mining machines. Proposed Sec. 75.824 addresses electrical protection for high-voltage continuous mining machines. The effects of ground faults, overloads, electrical arcing, heating of conductors, and short circuits can have adverse consequences to the safety of miners. Effective electrical protection for continuous mining machines would reduce the potential for ignitions, fires, and miner exposure to energized equipment frames. The proposed rule would provide increased miner protection by incorporating the latest technology when using high-voltage continuous mining machines. (a) Trailing Cable Protection Proposed paragraph (a) of Sec. 75.824 would require that a circuit-interrupting device have adequate interrupting capacity and be rated for the maximum voltage of the circuit in which it is used. The device would be part of the short-circuit, overload, ground-fault, and undervoltage protection for the trailing cable and the mining machine. The purpose of requiring that the circuit-interrupting device be properly rated is to safely interrupt any circuit current in which it is intended to be used without damage to itself. The circuit- interrupting device must have a voltage rating that would ensure that the device would remain undamaged when subjected to the maximum voltage of the system. Short-circuit and overload protection prevent damage to cables and motors due to arcing and overheating, and, therefore, minimize the risk of ignition and fire hazards to miners. Ground-fault protection minimizes the risk of shock and electrocution hazards to miners. Undervoltage protective devices prevent automatic restarting of equipment following a loss of power. This would prevent the inadvertent movement of machinery that can place miners at risk. (1) Short-Circuit Protection Proposed paragraph (a)(1)(i) would specify a current setting for a short-circuit protective device. The device, located in the power center, would be required to be set at the lower value of either the setting specified in approval documentation pertaining to the continuous mining machine or 75 percent of the minimum available phase- to-phase short-circuit current at the continuous mining machine. The short-circuit current settings specified in our approval documentation are based on the design of the continuous mining machine. As equipment is used and moved from one location to another in a mine, changes may take place in the electrical system which require an adjustment to the short-circuit protective device setting. Proposed paragraph (a)(1)(ii) would allow the short-circuit device protecting the cable extending from the power center to the continuous mining machine to have an intentional time delay. The short-circuit protective device located in the power center would be required to have the lower value of either the time delay setting specified in the approval documentation or up to 0.05 seconds. The purpose of permitting a time delay is to eliminate nuisance tripping during motor starting. When high-voltage longwalls were introduced to the mining industry, nuisance tripping problems were experienced. This nuisance tripping was caused by motor starting currents. To solve these problems, it was necessary to incorporate time delays into the short-circuit protective devices. Currently, electronic relays that are commonly used to provide short-circuit protection for high-voltage continuous mining machine circuits are designed with inherent time delay to override motor starting currents. (2) Ground-Fault Protection Proposed paragraph (a)(2) of Sec. 75.824 would require ground- fault protection for the trailing cable extending from the power center to the continuous mining machine. Proposed paragraph (a)(2)(i) would require ground-fault currents to be limited by a neutral grounding resistor to not more than 0.5 ampere. Neutral grounding resistors are used in resistance grounded systems to limit the level of ground fault current in a circuit. The use of a 0.5 ampere neutral grounding resistor in conjunction with the ground-fault devices specified in the proposed standard would reduce the potential for shock hazards and prevent the neutral grounding resistor from overheating and becoming a fire hazard. Proposed paragraph (a)(2)(ii) would require the trailing cable extending to the continuous mining machine to be protected by a ground- fault device set at not more than 0.125 ampere. The 0.125 ampere limit is based on the fact that sensitive ground-fault devices are commercially available and have been successfully used to detect ground-fault currents in circuits with extremely large values of motor starting current. The ground-fault device would have to operate within 0.050 second when exposed to 0.125 or more ampere. The purpose of permitting a time-delay is to prevent nuisance tripping during motor starting. The proposed time-delay requirement of paragraph (a)(2)(ii) is new. The granted PFMs require instantaneous ground-fault protection, and do not allow for any time delay. However, with higher inrush currents, the lower settings of the relay may cause the circuit to open during motor starting. Proposed paragraph (a)(2)(iii) of Sec. 75.824 would require an impedance-measuring ``look-ahead'' circuit to detect a ground-fault condition and prevent the closing of a circuit-interrupting device when a ground-fault exists in a circuit. The practice of repeatedly closing the circuit-interrupting device with a fault present can cause the circuit-interrupting device insulation to fail and cause the device to explode. This requirement is intended to reduce possible injury to miners from such potential explosion. Proposed paragraph (a)(2)(iv) of Sec. 75.824 would require that a high-voltage circuit extending from the power center to the continuous mining machine have back-up ground-fault protection to detect an open neutral grounding resistor. The back-up ground-fault protective device can be a combination of a potential transformer and voltage relay, or any other device capable of detecting an open neutral grounding resistor. Once an open neutral grounding resistor is detected, the back-up device must cause the circuit extending from the power center to the continuous mining machine to be de-energized. The 40 percent trip level would provide a safety factor to ensure that unexpected lower levels of ground-fault current would be detected and cause the circuit-interrupting device to open. Additionally, the back-up device must have a time-delay setting of not more than 0.25 second. The time- delay setting would be low enough to ensure quick de-energization of the circuit when the neutral resistor opens and a ground-fault exists, while allowing for selective tripping with the ground-fault protective device of the trailing cable. Proposed paragraph (a)(2)(v) of Sec. 75.824 would require thermal protection for the high-voltage neutral grounding resistor that would open the ground-wire monitor for the high-voltage circuit supplying the power center if the neutral grounding resistor is subjected to high- temperature resulting from a sustained ground-fault current. Thermal protection could include current transformers and thermal relays or any other devices, such as thermostats that sense overtemperature. The thermal device must not depend on control power because a loss of control power could prevent the detection devices from operating. The overtemperature rating or setting of the device would be the lower value of either 50 percent of the maximum temperature rise of the neutral grounding resistor or 302[deg] F (150[deg] C). A thermal device is an added safety feature which would cause interruption of the high-voltage circuit supplying the power center by opening the ground-wire monitor circuit before sustained extreme heat causes the neutral grounding resistor to fail in the open mode. Failure of the resistor could leave the circuit unprotected against ground faults and would increase the possibility of fire and shock hazards. The proposed overtemperature setting requirement would ensure that the affected circuit is quickly de-energized under a sustained fault. Our experience has been that the settings specified would be high enough to prevent nuisance tripping. Proposed paragraph (a)(2)(vi) of Sec. 75.824 would require a single window-type current transformer to encircle the three-phase conductors for ground-fault protection. It would also prohibit the equipment grounding conductors from being passed through the ground- fault current transformer. This configuration would be prohibited because it would defeat ground-fault protection and result in hazardous voltage on equipment frames. Using the single-window type current transformer in conjunction with a ground-fault relay would ensure sensitive ground- fault protection for circuits extending from the power center to the continuous mining machine. Proposed paragraph (a)(2)(vii) would require a ground-fault test circuit for each ground-fault device specified in proposed paragraph (a)(2)(ii) of this section. This test circuit would be required to inject a current of 50 percent or less of the current rating of the neutral grounding resistor to verify that a ground-fault condition will cause the corresponding circuit-interrupting device to open. This test procedure would help determine if ground-fault devices function at required current levels. It would also test the sensitivity of each device to ground fault currents. (3) Undervoltage Protection Proposed paragraph (a)(3) of this section would require that the undervoltage device operate on a loss of voltage, de-energize the circuit, and prevent the equipment from automatically restarting. This provision is performance oriented. It would permit any undervoltage protective device that operates on loss of voltage and which prevents the automatic closing of the circuit-interrupting device upon restoration of power, to be used. This requirement is intended to reduce the likelihood that miners will be pinned or crushed due to the automatic restarting of the equipment upon restoration of power. (b) Reclosing Proposed paragraph (b) of Sec. 75.824 would prohibit the use of circuit-interrupting devices that automatically reclose after opening. Automatic reclosure of the circuit-interrupting device would allow a circuit that has sustained a fault to re-energize. Typically, faults occur in trailing cables as a result of damage from roof falls or equipment. Under such circumstances, the use of automatic reclosing circuit-interrupting devices could create shock and fire hazards if the devices were designed to automatically reclose when a short-circuit or ground-fault condition exists in the circuit. (c) Onboard Power Circuits Proposed paragraph (c) of Sec. 75.824 would require a mine operator to implement certain procedures if a grounded-phase indicator light was provided on a high-voltage continuous mining machine, and it indicated a grounded-phase condition. The purpose of proposed paragraph (c) would be to warn miners of a grounded-phase condition. With ungrounded systems, the capacitive coupling between each phase conductor and ground can subject the ungrounded system to dangerous overvoltages from intermittent ground faults which can lead to insulation failure. Insulation failure can lead to another phase-to-ground failure. When two phases are grounded, a double-phase-to-ground or short-circuit condition will occur. High fault current will travel through the continuous mining machine frame creating possible shock and arcing hazards. The indication of a grounded-phase condition and subsequent repair of the equipment would reduce shock hazards to miners and eliminate any arcing ground-fault which can be an ignition source for methane. Therefore, it is important to detect and correct any grounded-phase condition. Proposed paragraphs (c)(1) and (2) of this section set out safe procedures to be followed when locating and correcting a grounded-phase condition. Proposed paragraph (c)(1) requires that once the grounded- phase indicator light on the high-voltage continuous mining machine shows that a grounded-phase fault has occurred, the mining machine must be immediately moved to an area where the roof is supported. Proposed paragraph (c)(2) requires that once a grounded-phase fault has occurred, the machine not be placed into operation until the grounded- phase condition is corrected or the machine be taken out of service. The intent of proposed paragraph (c)(1) is to minimize miners' exposure to roof falls while the equipment is being repaired. The intent of proposed paragraph (c)(2) is to protect the miners from shock hazards. Section 75.825 Power Centers Except for paragraph (f), each paragraph in this proposed section is derived from granted PFMs for the use of high-voltage continuous mining machines. This section proposes requirements for power centers supplying high-voltage continuous mining machines. The proposed rule addresses disconnecting switches and devices, barriers and covers, interlocks, emergency stop switches, grounding sticks, and caution labels. Compliance with these requirements will prevent shock, fire, and explosion hazards. (a) Main Disconnecting Switch Proposed paragraph (a) of this section would require a main disconnecting switch in the power center. The purpose of the main disconnecting switch is to de-energize the primary windings of all power transformers in the power center when the switch is open, except for the control power transformer(s) and feed-through circuit(s). This will provide a safe means of de-energizing power when performing electrical work. (b) Trailing Cable Disconnecting Devices Proposed paragraph (b) would require a disconnecting device for each high-voltage output used to power the continuous mining machine. Disconnecting devices in power centers facilitate the de-energization process prior to performing electrical work. Traditionally, we have accepted either a disconnecting switch or cable coupler to satisfy lock-out and tagging requirements. This proposed paragraph would ensure that disconnecting devices are available for lock-out and tagging purposes as required in proposed Sec. 75.831 to avoid exposing miners to electrical shock hazards. (c) Disconnecting Switches Paragraphs (c)(1) and (c)(2) of this section would require each disconnecting switch to have voltage and current ratings compatible with the circuits in which they are used. This requirement would prevent insulation failure and overheating resulting from using improperly rated switches. Therefore, this requirement would ensure that these switches would not create a shock or fire hazard to miners. Paragraph (c)(3) of this section would require that the disconnecting switch be designed and installed so that one could see, without removing any covers, that the contacts of the device are open when the switch is in the ``open'' position. The removal of any cover to verify that the contacts are open could expose personnel to energized high-voltage circuits and could increase the potential for shock hazard. Proposed paragraph (c)(4) would require the disconnecting switch to ground all power conductors on the ``load'' side of the switch when it is ``open and grounded.'' This requirement would ensure discharging of any existing voltage caused by capacitance between the power conductors and ground. It would also ensure that work can safely be performed on the electric circuits and equipment. Grounding the circuit would prevent shock hazards to miners working on the trailing cable or continuous mining machine. Proposed paragraph (c)(5) would require that each disconnecting switch be designed so that it can only be locked in the ``open and grounded'' position. The switch must not have the ability to be locked in the closed position because it could delay opening the switch during an emergency. This provision in conjunction with proposed Sec. 75.831 would ensure that the circuit remains de-energized until work is completed. Proposed paragraph (c)(6) would require a disconnecting switch to be capable of interrupting the full-load current without causing damage to itself and thereby creating hazardous conditions. Using a switch that is not capable of interrupting the full-load current could result in its destruction and in injuries to miners from flash burns or flying parts. If the switch is not designed for full-load current interruption, the proposed rule would require that the switch be designed to cause the circuit-interrupting device to de-energize the incoming power to the ``line'' side of the switch before the disconnecting switch interrupts the circuit. Proposed paragraph (c)(7) of Sec. 75.825 would require each disconnecting switch to be labeled to identify which circuit it would de-energize. We believe that identifying the correct circuit would assist miners in ensuring that the proper circuit is de-energized protecting them from exposure to electrical hazards. (d) Barriers and Covers Proposed paragraph (d) would require all compartments that provide access to high-voltage conductors or parts to have a barrier or cover to prevent miners from contacting high-voltage circuits. Therefore, low- or medium voltage circuits, including control circuits, must be separated by a barrier from high-voltage circuits if they are located in the same compartment. If the barrier was made of conductive material, it would need to be grounded to the power center frame. All control devices, other than those mounted on the high-voltage circuit- interrupting device, would need to be mounted so that they are separated from high-voltage parts. The purpose of this requirement is to minimize miners' exposure to high-voltage conductors or parts while working on or troubleshooting the control circuit. Miners would be protected against shock hazards that could arise from inadvertent contact with energized high-voltage circuits. (e) Main Disconnecting Switch and Control Circuit Interlocking Proposed paragraph (e) of this section addresses the interlock requirements of the main disconnecting switch with the control circuit. The proposed interlock would allow the control circuit in the power center to be energized only through an auxiliary switch in the ``test'' mode when the main disconnecting switch is in the ``open and grounded'' position. When the main disconnecting switch is in the ``open and grounded'' position, the power conductors on the load side of the disconnecting switch are grounded. The interlocking feature would ensure that before the auxiliary switch can be placed in the ``test'' position, the main disconnecting switch must be open and grounded. When the main disconnecting switch is ``closed,'' the control circuit can only be powered through the normal position and the control circuit cannot be tested. In the normal position, removal of a cover for testing would cause the cover interlock switches to de-energize incoming power. These interlock requirements are intended to prevent energization of the high-voltage circuits during testing and troubleshooting. (f) Interlocks Proposed paragraph (f) of this section is derived from the granted PFMs for the use of high-voltage continuous mining machines. The PFM provisions included the wording ``cover interlock switches,'' but did not specify the number of interlock switches required. Proposed paragraph (f) clarifies this by requiring at least two interlock switches to be installed on the cover or removable barrier of any compartment containing high-voltage conductors or parts. Proposed paragraph (f) would also require that the switches be installed so that removal of a cover or barrier will cause the switches to de-energize high-voltage conductors or parts located behind the removed cover or barrier. Magnetic or whisker-type switches are acceptable. Our experience with inspecting plunger-operated switches has revealed that these switches may stick and not operate effectively after exposure to the mine environment. We believe that at least two switches coupled with required maintenance under 30 CFR 75.512 would provide the necessary protection to any miners (including qualified persons) who mistakenly remove a cover or barrier, by ensuring that the high-voltage circuits are de-energized whenever a cover is removed. This would protect miners from accidental contact with energized high-voltage circuits. At times, qualified persons may need to remove covers and barriers when testing or troubleshooting energized power center control circuits. Proposed Sec. 75.825(f) requires that the interlocks on the covers or barriers isolating energized high-voltage conductors or parts de-energize incoming power. The intent of proposed paragraph (f) permits bypassing cover and barrier interlocks that isolate de- energized high-voltage conductors or parts. To bypass the cover and barrier interlocks, proposed paragraph (e)(1) of this section requires the qualified person to open the main disconnecting switch and place the control circuit auxiliary switch in the test position. This would permit the removal of covers or barriers when testing or troubleshooting the power center control circuits. For proposed paragraph (f) we are also considering revising the requirement that interlocks de-energize high-voltage circuits when covers and barriers are removed by adding an exception for troubleshooting control circuits. We specifically request your comments on this. (g) Emergency Stop Switch Proposed paragraph (g) of Sec. 75.825 requires an emergency stop switch that is located on the outside of the power center and that would de-energize the incoming high-voltage to the power center should an emergency arise. We would require that the switch be hard-wired to a fail-safe ground-wire monitor. In emergency situations, reliability of the stop-switch is critical. (h) Grounding Stick Proposed paragraph (h) would require that the power center be equipped with a grounding stick to discharge high-voltage capacitors and circuits. Because capacitors are energy storage devices, they continue to be energized even after the disconnecting switch is opened. Therefore, the use of a grounding stick would ensure that a qualified person would not be exposed to energized high-voltage conductors or parts. While there is no industry definition, we consider a grounding stick to be a live line tool (hot stick) made of either wood or fiberglass. To safely discharge the capacitors and parts, we recommend a hot stick with a No. 1/0 A.W.G. copper conductor bonded to the tool end of the hot stick and to the power center frame. This provision would also require a label that identifies the location of the grounding stick so that a qualified person can easily find it. The grounding stick would be required to be stored in a dry location to maintain its effectiveness. (i) Caution Labels Proposed paragraph (i) would require that all compartments providing access to energized high-voltage conductors and parts display a caution label that warns miners against entering the compartment before de-energizing the incoming high-voltage circuits to the compartment. It should remind miners that the line side of a disconnecting switch remains energized when the switch is opened unless the incoming power to the switch is de-energized. Section 75.826 High-Voltage Trailing Cables Proposed Sec. 75.826 specifies the requirements for high-voltage trailing cables. The requirements of this section are derived from granted PFMs for the use of continuous mining machines, existing Sec. Sec. 75.804 and 75.822, and existing and proposed part 18. Proposed paragraph (a) would require that the high-voltage trailing cables meet the requirements under Sec. 18.35 and proposed Sec. 18.54 of this title. Any high-voltage cable used as a trailing cable and meeting the design requirements of existing Sec. 18.35 and proposed Sec. 18.54, would be permitted to be used with high-voltage continuous mining machines. Proposed paragraph (b) of this section would provide two options. The first option would permit a cable meeting the requirements of existing Sec. 75.804. Section 75.804 requires, among other things, the use of a ground-check conductor not smaller than a No. 10 A.W.G. The reason it requires this minimum size is because the conductor is located on the periphery of the cable. When the cable is flexed the ground-check conductor is subjected to a larger bending radius that can weaken the ground-check conductor and cause it to break or become damaged. This option permits a ground-check conductor no smaller than the No. 16 A.W.G. to be located in the center of the cable. This design does not subject the ground-check conductor to the same stresses as the first option when the cable is flexed. The main advantage to this design versus the existing design in Sec. 75.804 is the reduction of inter-machine arcing because the cable design contains three grounding conductors placed symmetrically. We have seen this cable design successfully used with high-voltage longwall equipment. The second option would also eliminate the need to petition Sec. 75.804(a) when the cable is designed with a ground-check conductor smaller than No. 10 A.W.G. but not smaller than a No. 16 A.W.G. Section 75.827 Installation and Guarding of Trailing Cables Proposed Sec. 75.827 is partially derived from granted PFMs for the use of high-voltage continuous mining machines and paragraph (a)(3) is new. This section would require that trailing cables be installed and guarded according to the specific standards set forth in the provision. The purpose of this section is to protect high-voltage trailing cables from damage. Cable damage that results in exposed energized conductors would be a shock hazard to miners. (a) Trailing Cable Installation Proposed paragraph (a) would require that the trailing cable from the power center to locations specified in (a)(1), (2), or (3) be either supported on insulators or located in an unused entry. If the cable is located in a high seam mine and supported on insulators, it is less likely to be damaged by equipment running into or over it. A damaged cable may expose energized conductors, and thereby present a shock hazard to miners. While supporting the cable on insulators in a high seam mine would protect the cable from damage and the miner from shock hazards, the same would not be true for a low seam mine. Consequently, we are proposing the option of allowing the cable to be located in an unused entry to achieve the same protection. Permitting the cable to be located in an unused entry would provide flexibility for mine operators, while maintaining the same measure of protection for miners. Although this option was not in most earlier granted PFMs for the use of high-voltage continuous mining machines, the option was allowed in recently granted PFMs for use of these machines. We request comments on this provision for other methods of installing and protecting the high-voltage trailing cable. If the cable is located in an unused entry, the proposed rule would require that barricade tape and warning signs be used to alert miners that high-voltage cables are present. This proposed rule would not preclude foot travel but would warn operators of mobile equipment against traveling into the entry and running over the cable. An acceptable method to comply with both the barricade tape and warning sign requirements would be the use of pre-printed tape that displays a warning such as ``DANGER HIGH-VOLTAGE CABLE.'' Proposed paragraph (a)(1) would require the cable to be supported on insulators or placed in a barricaded, unused entry from the power center to the last open crosscut during advance mining. Proposed paragraph (a)(2) would require the cable to be supported on insulators or placed in a barricaded, unused entry from the power center to within 150 feet from any pillar workings during second mining. Second mining is defined in existing 30 CFR 75.332(b)(1) as ``intentional retreat mining where pillars have been wholly or partially removed, regardless of the amount of recovery obtained.'' Proposed paragraph (a)(3) would require the cable to be supported on insulators or placed in a barricaded, unused entry from the power center to within 150 feet of the continuous mining machine when the machine is used in outby areas. Examples of continuous mining machine usage in outby areas would include, but not be limited to, cutting overcasts, underpasses and sumps, and cleaning rock falls. A cable extending beyond the locations specified in proposed paragraphs (a)(1), (2), and (3) does not have to be supported on insulators or placed in an unused entry. Furthermore, we believe that supporting the cable beyond the specified locations would be impractical because of the dynamics of the mining process. Consequently, the provision does not require that the cable be supported beyond these locations. (b) Temporary Storage of Cables Proposed paragraph (b) would allow the temporary lacing of cable into a sled or crosscut to store the slack cable in those areas specified in paragraphs (a)(1) to (a)(3) of this section. Proposed paragraph (b) is an exception to proposed paragraph (a) which requires that the trailing cable be either supported on insulators or located in a barricaded, unused entry. A sled or crosscut would be required to be barricaded to prevent mobile equipment from running over the cable in those areas specified in paragraphs (a)(1) to (a)(3) of this section. Warning signs would also be required to alert miners to the existence of an energized, high-voltage cable. Barricade tape pre-printed with a warning such as ``DANGER HIGH-VOLTAGE CABLE'' would meet the intent of the proposed rule. The temporary storage requirements of this paragraph are intended to protect the cable from damage and miners from contacting the energized cables. (c) Guarding Proposed paragraph (c)(1) of Sec. 75.827 would require that the high-voltage cable be guarded at certain locations. These locations are those sections of the cable where miners are likely to come in contact with the cable and where the cable may be subject to possible damage. All guarding would be required to fully cover the cable in the areas specified in (c)(1)(i)-(iii) to provide a physical barrier between the cable and the miners. While guarding might cover a damaged cable, the damaged cable should be repaired immediately or removed from service as required by existing Sec. 75.512. The purpose for requiring guarding is to protect the miner from shock hazards and protect the cable from damage rather than for the purpose of repairing the cable. Proposed paragraph (c)(2) would require that guarding be constructed from grounded metal or nonconductive flame-resistant material. If a marking does not appear on the guarding to indicate that it is flame-resistant, we will request documentation to substantiate the flame-resistance quality. Metal and non-conductive guarding could be either a continuous length or overlapping shorter pieces. Shorter pieces of metal guarding would need to be bonded together to ensure a continuous metallic path. In addition, metal guarding would have to be bonded and grounded. Additionally, if the cable becomes damaged so that high-voltage conductors become exposed, it can create a shock hazard for miners. If grounded metal guarding is used, it would activate the ground-fault protection and de-energize the cable. If non-conductive guarding is used, it would isolate miners from the exposed, energized conductors. Therefore, the use of these materials would help prevent miners from being exposed to shock hazards if they contact the guarding when energized conductors are exposed. (d) Suspended Cables and Cable Crossovers Proposed paragraph (d)(1) offers a mine operator two options for protecting the high-voltage trailing cable in or inby the last open crosscut when equipment must cross any portion of the cable. The option provided by proposed paragraph (d)(1)(i) would require the high-voltage trailing cable to be suspended from the roof in those mines where sufficient clearance exists so that mine equipment will not damage the cable. The option provided by proposed paragraph (d)(1)(ii) would require that the high-voltage trailing cable be protected by a commercially available cable crossover. Where sufficient clearance from the mine equipment to the mine roof does not exist, a mine operator must use the option in proposed paragraph (d)(1)(ii). Cable crossovers are commercially available and have been used throughout the industry to protect cables from being damaged by equipment. These provisions help ensure that the high-voltage trailing cable is protected from damage by moving equipment. If possible, work procedures should be developed to minimize the need for suspending the cable or using cable crossovers. Proposed paragraph (d)(2) specifies the minimum design requirements for the cable crossovers. These minimum design requirements are intended to ensure that mine operators consider both equipment size and type in use at their mine so that the equipment is able to cross over the cable without damage to the cable. For example, mines that use track mounted equipment should use crossovers capable of preventing damage to the cable from the equipment track cleats. It has been our experience that cable crossovers provide protection to cables when properly used. Section 75.828 Trailing Cable Handling and Pulling Proposed Sec. 75.828(a) is derived from granted PFMs for the use of high-voltage continuous mining machines. Proposed paragraph (a) addresses the types of personal protective equipment required to be used when it is necessary to handle energized cables. Proposed Sec. 75.828(b) is new, and is based on our concern that cable damage may result from improper pulling. Paragraph (b) would require de-energizing the cable and following the manufacturer's procedures for pulling the cable by equipment other than the continuous mining machine. (a) Handling Proposed paragraph (a) of this section would prohibit handling energized high-voltage trailing cables without wearing properly tested and rated insulating gloves. The provision would require that testing and rating of the insulating gloves be in accordance with proposed Sec. 75.833. In addition, paragraph (a) would require that if mitts, hooks, tongs, slings, aprons, or other personal protective equipment are used to handle the energized cable, insulating gloves must also be used. This would ensure that miners are protected against shock hazards while handling energized cables. (b) Pulling Proposed paragraph (b) of Sec. 75.828 would require that the trailing cable be de-energized prior to being pulled by equipment other than the mining machine. The proposed paragraph would also require that the cable manufacturers' pulling procedures be followed. Cable manufacturers' recommendations usually include: The proper application of a rope or sling to pull the cable; pulling procedures that will not exceed the minimum bending diameter; maximum length of trailing cable that can be safely pulled; and the number of corners that it can be pulled around. The purpose of this requirement would be to prevent damage to the cable. For example, when pulling cables with ropes, if a loop smaller than the minimum bending diameters for the size of the trailing cables being pulled is created, the cable can be damaged. Proper pulling procedures would minimize cable damage and protect miners against shock hazards. Section 75.829 Tramming Continuous Mining Machines In and Out of the Mine, and From Section to Section Proposed Sec. 75.829 is partially derived from granted PFMs for the use of high-voltage continuous mining machines, and proposed Sec. 75.901. High-voltage continuous mining machine PFMs include requirements for either using a portable transformer that supplies 995- volts to the hydraulic pump motor and controls, or a temporary onboard step-up transformer to power the 2400-volt hydraulic pump motor and controls on the machine. In addition to these two options, the Agency has granted petitions to modify Sec. 75.901 to allow the use of low-/ medium-voltage, three-phase, diesel-powered generator sets to move section equipment. We anticipate the need to use high-voltage diesel- generator sets to move high-voltage continuous mining machines. In developing this section, we envisioned the use of the following power sources to tram the continuous mining machine: a medium-voltage power source, an onboard step-up transformer, and a high-voltage diesel generator set to energize the hydraulic pump motor and controls of the continuous mining machine. (a) Conditions of Use Proposed paragraph (a) of this section sets forth the general requirements when using any of the power sources specified in paragraph (c) of this section for moving continuous mining machines. Proposed paragraph (a)(1) of this section is derived from Sec. 75.500 which prohibits equipment not approved by us as ``permissible'' to be taken into or used in specific areas of the mine. Typically, these power sources are not ``permissible'' and, therefore, must not be permitted in these areas. Proposed paragraph (a)(2) is new. It would require that the continuous mining machine not be used for mining or cutting while being trammed from section-to-section or in or out of the mine if the mining machine is powered by a medium-voltage power source, an onboard step-up transformer, or a high-voltage diesel-generator set. However, if mining or cutting is required, a power center that meets the requirements of Sec. 75.825 must be used. In granted PFMs, the power sources permitted for tramming the continuous mining machine included rewiring of the input to use 995 volt for tram and control functions, or an onboard step-up transformer. Typically these sources do not have the capacity to power the continuous mining machine for mining or cutting functions. Proposed paragraphs (c)(1) and (c)(2) are identical to the PFM requirements, while proposed paragraph (c)(3) permits the use of a high-voltage diesel generator. If mining or cutting were attempted while the machine is powered by these power sources, overloading and loss of power could occur. Typically these power sources are not of sufficient size to power all motors on the continuous mining machine for mining or cutting purposes. Proposed paragraph (a)(3) would require that low-, medium-, and high-voltage cables comply with existing Sec. Sec. 75.600-1, 75.907, and proposed Sec. 75.826 when using the power sources specified in paragraph (c) of this section for moving continuous mining machines. Existing Sec. 75.600-1 requires flame-resistant cables, existing Sec. 75.907 specifies the design requirements for medium-voltage trailing cables, and proposed Sec. 75.826 specifies the design requirements for high-voltage trailing cables. Proposed paragraph (a)(4) would require that the high-voltage cable be secured on-board the mining machine. When using an on-board step-up transformer or a diesel-generator set, as permitted in proposed paragraphs (c)(2) and (c)(3), respectively, of this section, the energized high-voltage cable would need to be secured on-board the mining machine. If the trailing cable does not fit on the machine, a shorter length of cable should be substituted to connect the diesel- generator output to the continuous mining machine. The purpose of this requirement is to prevent anyone from handling energized, high-voltage cables and to minimize cable damage while tramming the continuous mining machine. (b) Testing Prior to Tramming Proposed paragraph (b) of Sec. 75.829 is derived from granted PFMs to modify Sec. 75.901 to allow the use of low- and medium-voltage diesel generators. Proposed paragraph (b)(1) would require that a qualified person conduct ground-fault and ground-wire monitor tests on the power sources specified in proposed paragraph (c) of this section, and that the circuits pass these tests prior to moving the continuous mining machine. If these tests indicate equipment failure, paragraph (b)(1) would require the mine operator to comply with proposed Sec. 75.832(f), and correct the defect prior to moving the mining machine. Paragraph (b)(1) would also require that the qualified person record the results of the tests, and the mine operator maintain a record of the tests for one year as required by proposed Sec. 75.832(g). The ground-fault test would verify that the circuit will be de-energized when a ground-fault condition exists. Power center manufacturers provide test circuits so ground-fault protection can be tested without subjecting the power system to an actual ground-fault condition. The ground-wire monitor test would verify that the circuit will be de- energized when the ground-check or grounding circuit is opened. Ground- wire monitor manufacturers provide a built-in test switch for this purpose. Ground-wire monitors would be required when low and medium power sources are used as permitted by proposed paragraphs (c)(1)(i) and (c)(2)(i) of this section. Ground-wire monitors would not be required when the provision of this section requires the use of external bonding for high-voltage equipment. A ground-wire monitor would not be required for high-voltage circuits of power sources specified in proposed paragraphs (c)(2) and (c)(3). In these applications, external bonding required by proposed Sec. Sec. 75.829(c)(2)(iii)(B) and 75.829(c)(3)(ii) would be used to connect the frames of high-voltage equipment together. Proposed paragraph (b)(2) would require that prior to tramming the continuous mining machine, a responsible person designated by the operator, test the grounded-phase detection circuit on the high-voltage continuous mining machine to ensure that the detection circuit would detect a grounded-phase condition. This is the same requirement as proposed Sec. 75.832(e), except the test needs to be conducted prior to tramming. If these tests indicate equipment failure, the mine operator must comply with proposed Sec. 75.832(f), and correct the defect prior to moving the mining machine. Proposed paragraph (b) would not require a repeat of the ground- fault, ground-wire monitor, and grounded-phase tests when a continuous mining machine is stopped intermittently while tramming. The purpose of this paragraph is to require that functional tests be performed before the equipment begins its move from the surface to underground, from underground to the surface, or moves from one part of the mine to another. It does not require a functional test after momentary or incidental stoppage during the moving process. This method of testing enhances safety by preventing miners from being exposed to energized circuits while performing the test. The combination of the ground-fault, ground-wire monitor, and grounded- phase tests would ensure safety devices operate to protect miners from shock hazards should a fault condition occur. (c) Power Sources Proposed paragraph (c) would specify power sources, in addition to the power center, that may be used when the mining machine is moved in and out of the mine or from section to section. Power sources specified in this section have been selected to avoid the need to handle energized, high-voltage cables. (1) Medium-Voltage Power Source Proposed paragraph (c)(1) of Sec. 75.829 is derived from the granted PFMs for the use of high-voltage continuous mining machines. This option would allow the use of a medium-voltage power source that supplies 995 volts to the continuous mining machine. Figure 1 in this section illustrates a high-voltage continuous mining machine using a 995 volt power source. The power source can be supplied by the mine's power system, or a low- or medium-voltage diesel-generator set. If the power source is a portable transformer, the proposed rule would prohibit moving the transformer while energized. However, if a low- or medium-voltage diesel-generator set is used as a power source, the rule would permit the generator set to be moved while energized. If a diesel generator supplies power to a separate portable transformer, the proposed rule would prohibit the transformer from being moved while energized. To use the option in this paragraph, the machine circuitry would need to be rewired to allow the medium-voltage to energize the tram and hydraulic pump motor circuits. Backfeeding the continuous mining machine power transformer with medium voltage to energize the high-voltage circuit would be prohibited. In addition, the mine operator would have to comply with the applicable provisions in Sec. Sec. 75.500 through 75.1000, such as overcurrent, ground-fault, undervoltage, and ground-wire monitors. (2) Onboard Step-Up Transformer Proposed paragraph (c)(2) of Sec. 75.829 is derived from granted PFMs for the use of high-voltage continuous mining machines. It would allow the use of a temporary onboard step-up transformer. The transformer would convert low- or medium-voltage to high-voltage to power the continuous mining machine. Figure 2 in this section illustrates this configuration. Proposed paragraph (c)(2)(i) would require low- or medium-voltage to comply with applicable requirements in 30 CFR part 75. For example, overcurrent, ground-fault, and undervoltage protection required in Subpart J are applicable. Proposed paragraph (c)(2)(ii) would require that the high-voltage output circuit of the transformer comply with proposed Sec. 75.824. For a detailed discussion of these requirements see the section-by- section discussion to proposed Sec. 75.824. Proposed paragraph (c)(2)(iii) would require that the transformer be securely installed on-board the continuous mining machine to prevent it from falling off the machine and to minimize vibration. Vibration could lead to an internal ground-fault or damage to the transformer. The frame of the on-board temporary transformer would be required to be bonded to the continuous mining machine frame and the metallic shell of each cable coupler by at least a No. 1/0 A.W.G. or larger conductor, and connected to the incoming ground wire of the trailing cable. This would ensure a low impedance grounding path from the onboard transformer to the outby power source should a ground-fault occur. Paragraph (c)(2)(iii)(C) would require that the transformer be equipped with at least two interlock switches for each cover and an external emergency stop switch to de-energize outby power when activated. (3) Diesel-Generator Set Proposed paragraph (c)(3) of Sec. 75.829 is new. It contains requirements for using a diesel-generator set to supply high-voltage power for the continuous mining machine in certain circumstances. The first circumstance in which the requirements apply is when moving the continuous mining machine from section-to-section or in and out of the mine. The second circumstance is when the trailing cable to the continuous mining machine is providing high-voltage power from a high- voltage diesel generator set or a combination of a diesel generator set and a transformer. A diesel-generator set could be either a high-voltage generator or a combination of a low-, medium-, or high-voltage generator and a transformer. When the trailing cable to the continuous mining machine is providing low- or medium voltage from a diesel generator set or a combination of a diesel generator set and a transformer, proposed paragraph (c)(1) or (c)(2) would apply. If a low- or medium-voltage generator is to be used, it would require a PFM of existing Sec. 75.901, Protection of low- and medium-voltage three-phase circuits used underground. Figures 3 and 4 of this section illustrate the variations when the trailing cable connected to the continuous mining machine is energized with high-voltage from a diesel-generator power source. Proposed paragraph (c)(3)(i) would require a grounding resistor to satisfy two requirements. First, it would have to be rated for the maximum voltage to which it is subjected. Second, it would have to limit the ground-fault current to no more than 0.5 ampere. Requiring a grounding resistor rated for the maximum voltage would ensure that adequate insulating properties are provided for the grounding resistor. This is especially important when using autotransformers. When using an autotransformer, the grounding resistor would be required to be located between the neutral of the wye connected generator and the generator frame, and it must be rated for the highest output voltage of the autotransformer. A phase-to-ground fault occurring on the secondary side of the autotransformer would subject the grounding resistor to the output voltage of the autotransformer. This is because autotransformers have only one winding-per-phase and do not provide the electrical isolation characteristics necessary to create a separately derived system. A resistor that is subjected to a voltage higher than its rating can potentially explode, causing serious injury or death to persons nearby, or it can open from overcurrent, leaving the system ungrounded. Limiting the ground-fault current to not more than 0.5 ampere, and providing the sensitive ground-fault protection set forth in paragraphs (c)(3)(iv) provides increased protection against explosion, fire, and electrical shock. If an isolation transformer is used in conjunction with a high- voltage generator, another neutral grounding resistor would need to be connected between the neutral of the transformer and its frame. This provision is intended to limit the voltage on the frame of the generator, transformer, and continuous mining machine to prevent a shock hazard during ground-faults. Proposed paragraph (c)(3)(ii) would require bonding of the non- current carrying metal parts of the generator, transformer, and all cable couplers to the continuous mining machine using at least a No. 1/ 0 A.W.G. grounding conductor. This would eliminate any potential differences between equipment frames and provide a low impedance path for ground-fault current. The external No. 1/0 A.W.G. grounding conductor would provide visual evidence of a ground-fault current path and offer mechanical strength and durability. The intent of this provision is to minimize miners' exposure to shock hazards. This provision would satisfy the requirements of existing Sec. 75.803, and eliminate the need for a ground-wire monitor. Proposed paragraph (c)(3)(iii) would require the generator set to be in close proximity to the continuous mining machine. This provision would eliminate the hazards associated with handling energized high- voltage cables discussed in proposed Sec. 75.828. Close proximity is intended to mean as close as practical using a solid connecting device to prevent free movement. This proposed paragraph would also require that the generator set and the continuous mining machine be securely attached by means of a tow-bar to prevent the generator set from moving freely. Chains, ropes, or slings would not be permitted as a sole means of preventing free movement. Compliance with this provision would limit the cable length between the generator and the continuous mining machine and thereby minimize cable handling and damage. Proposed paragraph (c)(3)(iv) would require each three-phase output circuit, from the generator and transformer when used, to be equipped with sensitive ground-fault protection. The ground-fault circuit would be required to consist of a single window (zero sequence) current transformer and an instantaneous ground-fault device that would cause the appropriate circuit-interrupting device to open and the diesel engine to shut down. Ground-fault devices must cause the circuit interrupting device to open at no more than 0.125 ampere. Additionally, the proposed rule would prohibit the equipment grounding conductor from passing through the ground-fault current transformer. Passing the equipment grounding conductor through the current transformer would prevent detection of any ground-fault current. Proposed paragraph (c)(3)(v) would require each three-phase circuit, from the generator and transformer when used, to be equipped with short-circuit and undervoltage protection. The purpose of short- circuit and undervoltage protection is discussed under proposed Sec. Sec. 75.824(a)(1) and 75.824(a)(3). Proposed paragraph (c)(3)(vi) would require a test circuit for each ground-fault device. The purpose of a test circuit is discussed under proposed Sec. 75.824(a)(2)(vii). Proposed paragraph (c)(3)(vii) would require labels to be mounted next to or on the instantaneous trip unit of each circuit interrupting device. This label would list the maximum circuit interrupting device setting allowed for short-circuit protection of the respective circuit. Since the minimum short circuit current is calculated using the maximum length of cable allowed, the label will assist in ensuring that adequate short circuit protection for each circuit is provided. Proper short-circuit settings will prevent sustained arcing during electrical faults and a subsequent fire hazard from occurring. Section 75.830 Splicing and Repair of Trailing Cables (a) Splices and Repairs Proposed Sec. 75.830(a) is derived from granted PFMs for high- voltage continuous mining machines. This proposed section addresses the training/qualifications and the manner in which the trailing cable is to be spliced to ensure that miners are not exposed to shock and burn hazards while splicing or repairing the cable. Proposed paragraph (a)(1) would require that cable splicing and repair be performed only by a qualified person who received specific training in cable splicing and repair of high-voltage cables. This training must be accomplished through the annual training under 75.153(g). The intent of this provision is to ensure that the person performing the splicing and repair of cable understands the construction of the cable, the purpose of every component, and the hazards associated with failure to replace each component with a component similar to the original. Proposed paragraph (a)(2) would require that the spliced or repaired cable provide the same degree of protection to miners as the original cable. The quality of workmanship is vital to maintaining the same level of protection to miners as provided by the original cable. Proposed paragraph (a)(3) would require that splices and repairs of trailing cables satisfy the requirements in existing Sec. 75.810. Existing Sec. 75.810, among other things, references existing Sec. 75.604 which requires that the spliced or repaired cable be mechanically strong and provide the same flexibility and conductivity as the original cable. It also requires that the cable be effectively insulated and sealed to exclude moisture. Moisture would minimize the insulation quality and could render the splice a potential shock hazard to miners. Further, the splice or repair would be required to have flame-resistant qualities and good bonding to the outer jacket. The trailing cable, which would be required to have shielding around each power conductor and a double jacketed protection, must be repaired using an MSHA-approved splice kit. These kits provide specific material and instructions to be used when splicing or repairing the cable to ensure that it is flame resistant. Using this material and following these instructions is necessary to ensure the flame-resistant quality of the cable, and avoid exposing miners to potential fire and shock hazards. (b) Permanent Cable Repair Proposed paragraph (b) is derived from granted PFMs for the use of high-voltage continuous mining machines, and would require that MSHA- approved high-voltage kits be used, which include instructions for outer-jacket repairs and splices. Because the outer jacket protects the cable from damage, it is important to use appropriate materials and follow proper procedures. The majority of PFMs included a provision to prohibit the use of temporary and/or permanent tape-type splices. The purpose of this prohibition was to prevent the use of non-vulcanizing tape from being used for splices or outer jacket repair. Regular tape repairs to high- voltage trailing cables do not exclude moisture which leads to insulation degradation and subsequent ground-fault conditions. When the materials in the MSHA-approved kits are properly applied, they will create a splice or outer jacket repair that will exclude moisture from the trailing cable. Since this proposed paragraph requires the use of an MSHA-approved high-voltage kit, this prohibition was not required. As explained before, improper high-voltage trailing cable repair can lead to miners' being exposed to shock and fire hazards. (c) Splicing Limitations Proposed paragraph (c) is derived from granted PFMs for the use of high-voltage continuous mining machines, and would prohibit splicing of the trailing cable within 35 feet of the continuous mining machine. Our experience with low- and medium-voltage equipment has shown that this portion of the cable is subjected to the most stresses and strains. If this portion of the cable is spliced, electrical connections in the splice can weaken and cause cable damage. This can lead to potential shock hazards to miners. In addition, this portion of the cable is handled by miners more often than the rest of the cable. Therefore, the probability of miners being shocked by an inadequate splice within this portion of cable would be greater. Section 75.831 Electrical Work; Troubleshooting and Testing Proposed Sec. 75.831 is derived from granted PFMs for the use of high-voltage continuous mining machines and existing Sec. 75.820. This section would specify safe procedures to be followed when performing electrical work, including troubleshooting and testing. (a) Trailing Cable and Continuous Mining Machine Electrical Work Procedures Proposed paragraph (a) would require that a qualified person de- energize the trailing cable circuit and complete one of the lock-out and tagging procedures specified in paragraphs (a)(1) or (a)(2) prior to performing electrical work on the trailing cable or continuous mining machine. De-energization is usually accomplished by opening the circuit-interrupting device. The qualified person must follow these work procedures to prevent inadvertent re-energization. These procedures are important to ensure that miners are not exposed to potential shock, fire, or other hazards when performing electrical work. Proposed paragraphs (a)(1) and (a)(2) of this section would specify the options available for lock-out and tagging procedures. Depending on the power center design, a disconnecting switch or a cable coupler can be used to lock-out and tag the trailing cable. Proposed requirement (a)(1) specifies work procedures if a disconnecting switch is used on the output circuit of the power center supplying power to the continuous mining machine. If a disconnecting switch is used, proposed paragraph (a)(1)(i) would require the switch to be opened to provide visual evidence that the output is de-energized and grounded. Proposed paragraph (a)(1)(i) would also require that the switch be locked in the open and grounded position and tagged. This would allow the cable coupler plug to remain connected to the power receptacle. Additionally, proposed paragraph (a)(1)(ii) would require the plug and receptacle to be locked together and tagged. The reason for this requirement is that we are concerned that someone may unplug the cable from the locked-out circuit and plug it into the spare circuit. When this option is used, a grounding receptacle would not be needed because opening the disconnecting switch grounds the high-voltage trailing cable. We are aware that some mine operators prefer not to disconnect the high-voltage couplers since it may lead to problems when re-energizing the circuit. The major problem caused by disconnecting the high-voltage couplers is the risk of contaminating the coupler's insulation system. Using a disconnecting switch to ground and isolate power from the trailing cable and continuous mining machine would eliminate the need to remove the cable coupler plug from the receptacle. Proposed paragraph (a)(2) would permit using the cable coupler as the disconnecting device instead of a disconnecting switch. After power has been removed, proposed (a)(2)(i) would require the plug to be disconnected from the receptacle and reconnected to a grounding receptacle. The grounding receptacle, which is mounted on the power center, would cause all cable conductors to be grounded to the power center frame. Connecting the plug to the grounding receptacle would ensure that no voltage would be present in the cable conductors. Proposed paragraph (a)(2)(ii) would require the plug and grounding receptacle to be locked together and tagged. Tagging would alert other miners that work is being done on the circuit, and the lock would prevent the circuit from being re-energized and ungrounded while work is being performed. These requirements would prevent shock hazards to miners while performing electrical work. Lastly, proposed paragraph (a)(2)(iii) would require placing a dust cover over the power receptacle to protect it from becoming contaminated by dust when the trailing cable is disconnected. Dust is a conducting medium and can create ground faults. Another benefit of using the dust cover is to prevent contact with parts of the receptacle that could be energized. (b) Trailing Cable Grounding Proposed paragraph (b) would require that a qualified person de- energize the trailing cable circuit as required in paragraph (a) and complete one of the lock-out and tagging procedures specified in paragraphs (b)(1) or (b)(2) prior to testing and troubleshooting the de-energized trailing cable. As discussed in proposed Sec. 75.831(a), de-energization is usually accomplished by opening the circuit- interrupting device. The qualified person must perform these work procedures to prevent inadvertent re-energization. These procedures are important to ensure that miners are not exposed to potential shock, fire, or other hazards when performing electrical work. Proposed paragraphs (b)(1) and (b)(2) of Sec. 75.831 would specify the lock-out and tagging options available for troubleshooting and testing the high-voltage trailing cable. As discussed in proposed paragraph (a)(1) of Sec. 75.831, when a disconnecting switch is used, it can open and ground the trailing cable circuit. Proposed paragraphs (a)(1)(i) and (b)(1)(i) would require the disconnecting switch to also be locked and tagged. Proposed paragraph (b)(1)(ii) would require the plug to be disconnected from the power receptacle. Proposed paragraph (b)(1)(iii) would require that a lock and tag be placed on the plug to prevent a miner from inserting the plug into a receptacle. Finally, proposed paragraph (b)(1)(iv) would require that a dust cover be placed over the power receptacle. These provisions would establish proper work procedures prior to testing and troubleshooting of the trailing cable. Proposed paragraph (b)(2) addresses the design where a switch is not provided. In this case, the cable coupler would be used as the disconnecting device instead of a disconnecting switch, to establish work procedures when troubleshooting and testing high-voltage trailing cables. Proposed paragraphs (a)(2)(i) and (b)(2)(i) of this section would require the plug to be disconnected from the power receptacle and connected to the grounding receptacle to ensure all power conductors are grounded. The plug could then be removed from the grounding receptacle. Proposed paragraph (b)(2)(ii) would require the plug to be locked and tagged to prevent it from being reconnected to any receptacle. Proposed (b)(2)(iii) would require that a dust cover be placed over the power receptacle to prevent insulation contamination. Troubleshooting and testing of the cable could then commence. (c) Trailing Cable Troubleshooting Proposed paragraph (c) of Sec. 75.831 would allow the trailing cable to be ungrounded only for the time necessary to locate a problem. Existing Sec. 75.705 requires that all high-voltage lines be de- energized and grounded before work is performed. This proposed rule allows for ungrounding the circuit when troubleshooting and testing. Once the problem is found and prior to re |