Low- and Medium-Voltage Diesel-Powered Electrical Generators, 77728-77739 [05-24625]

Agencies

• DEPARTMENT OF LABOR
• Mine Safety and Health Administration

[Federal Register Volume 70, Number 250 (Friday, December 30, 2005)]
[Rules and Regulations]
[Pages 77728-77739]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 05-24625]


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DEPARTMENT OF LABOR

Mine Safety and Health Administration

30 CFR Part 75

RIN 1219-AA98


Low- and Medium-Voltage Diesel-Powered Electrical Generators

AGENCY: Mine Safety and Health Administration (MSHA), Labor.

ACTION: Final rule.

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SUMMARY: This final rule amends an existing safety standard to allow 
the use of low- and medium-voltage diesel-powered electrical generators 
as an alternative means of powering electrical equipment in underground 
coal mines. The final rule eliminates the need for mine operators to 
file petitions for modification to use these portable generators to 
power electrical equipment and does not reduce the protections afforded 
miners by the existing standards, in fact it increases protections.

EFFECTIVE DATE: February 28, 2006.

FOR FURTHER INFORMATION CONTACT: Rebecca J. Smith, Acting Director, 
Office of Standards, Regulations and Variances, MSHA, 1100 Wilson 
Boulevard, Arlington, Virginia 22209-3939. Ms. Smith can be reached at 
smith.rebecca@dol.gov (Internet e-mail) (202-693-9443) (voice) or (202-
693-9441) (facsimile). The final rule also is available on the Internet 
at https://www.msha.gov/REGSINFO.HTM.

SUPPLEMENTARY INFORMATION: 

I. Background Information

    We (MSHA) are amending Sec.  75.901 to permit the use of low- and 
medium-voltage diesel-powered electrical generators as a means for 
providing a portable source of power to move equipment in, out, and 
around the mine and to perform work in areas where permissible 
equipment is not required. This final rule does not reduce the 
protections for miners in the current standards, but increases miner 
safety by updating the electrical requirements with new commercially-
available technology so miners may use diesel-powered electrical 
generators as a source of power. The final rule provides protective 
systems and testing procedures to limit the amount of voltage and 
current that miners can be exposed to under ground fault conditions; 
thus, it reduces the possibility of a fire, shock, or burn hazard when 
miners use these generators.
    Furthermore, by issuing this final rule, we are responding to the 
requirements of the Regulatory Flexibility Act and Executive Order 
12866 that agencies review their regulations to determine their 
effectiveness and to implement any changes indicated by the review that 
will make the regulation more flexible and efficient for stakeholders 
and small businesses. In accordance with the requirements of the Mine 
Act, Sec.  101(a)(9), this final rule does not reduce the protection 
afforded to miners by the existing standard.
    Generally, power centers are the main means of supplying 
electricity in an underground mine. Power centers are placed 
underground to provide power to permanent or stationary electrical 
equipment, such as belt conveyor drives, and to mining equipment on 
working sections. Power centers in areas where permissible equipment is 
not required are generally stationary. Mine operators use various means 
to move electrical equipment and to perform work in areas where 
permissible equipment is not required. In these situations, they are 
unable to use power centers to energize the machines for the move 
because of the excessive length of cable required to reach the power 
center. If longer trailing cables are installed in order to reach 
remote power centers, proper electrical protection for these low- and 
medium-voltage three-phase circuits may be compromised and overheating 
of, or damage to the cables may occur.
    Over a 13-year period (1990-2003), through our petition for 
modification (PFM) process, mine operators have been using low- and 
medium-voltage diesel-powered electrical generators as an efficient 
means for providing a portable source of power to move and operate 
electrical equipment in areas where permissible equipment is not 
required. These portable diesel-powered electrical generators are 
easily taken to areas where power centers or other sources of 
electrical power are not available to move mobile equipment or supply 
power to other electric equipment needed to do work in outby areas. 
Proper electrical protection for these low- and medium-voltage three-
phase circuits can safely be provided by portable diesel-powered 
electrical generators.
    Existing mandatory safety standards Sec.  75.701 (Grounding 
metallic frames, casings, and other enclosures of electric equipment) 
and Sec.  75.901 (Protection of low- and medium-voltage three-phase 
circuits used underground), specify the grounding requirements for 
electrical equipment and low- and medium-voltage three-phase circuits. 
However, when using these generators, mine operators are unable to 
comply with the existing electrical protection requirements of Sec.  
75.901. Currently, Sec.  75.901 requires a grounding circuit to 
originate from the grounded side of a grounding resistor located at a 
power center. In addition, Sec.  75.901 does not address the use of a 
generator frame for the purpose of grounding.
    To address their inability to comply with Sec.  75.901, mine 
operators file PFMs under section 101(c) of the Federal Mine Safety and 
Health Act of 1977 (Mine Act). PFMs may be granted when the Secretary 
determines that an alternative method of achieving the result of a 
standard exists that will at all times guarantee the same measure of 
protection afforded to miners under a standard, or when the application 
of a standard to the mine will result in a diminution of safety to the 
miners at the mine. 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 the mandatory 
standard at the individual mine. After

[[Page 77729]]

the PFM is issued, we continue to monitor compliance with its terms and 
conditions.
    During the time period January 1990 through October 2003, we 
granted 63 PFMs that requested the use of diesel-powered electrical 
generators. These PFMs affected 56 mines.
    The first petition granted for a modification of Sec.  75.901 was 
submitted to us in 1990, requesting the use of a diesel-powered 
electrical generator. In 1996, we determined that it was necessary for 
a mine operator to petition both Sec. Sec.  75.701 and 75.901 to allow 
the use of a diesel-powered electrical generator in underground coal 
mines. Petitioning both standards resulted in additional expense and 
paperwork burden for mine operators. To reduce the expense and 
paperwork burden for mine operators, we conducted a review of both 
standards in 2003 and determined that only a PFM of Sec.  75.901 was 
necessary because conditions for grounding contained in the petition 
will satisfy the requirement of Sec.  75.701 as an approved method of 
grounding.
    On June 25, 2004, we published a proposed rule (69 FR 35992) to 
amend the existing electrical standard Sec.  75.901 (Protection of low- 
and medium-voltage three-phase circuits used underground), which 
specifies the safety requirements for protecting low- and medium-
voltage three-phase circuits. This standard was published in 1970 (35 
FR 17890) and has not been changed.
    During November 2004, we held four public hearings on the proposed 
rule in Salt Lake City, Utah; Birmingham, Alabama; Lexington, Kentucky; 
and Morgantown, West Virginia. The post-hearing comment period closed 
December 10, 2004. In response to the proposed rule we received three 
written comments and oral testimony presented at the public hearings.

II. Discussion of Comments and Testimony Received

    During the public hearings, we received many comments which were 
not directly related to specific proposed provisions of the low- and 
medium-voltage diesel-powered electrical generators standard. Most of 
the comments were directed at enhancing other health and safety issues 
of miners, rather than addressing the electrical safety of grounding 
circuits for diesel-powered electrical generators. These comments are 
beyond the scope of this rule and they are addressed by other existing 
standards. We also received two comments concerning the number of PFMs 
granted and the purpose behind the proposed rule.
    Below is a discussion of the eight categories of comments we 
received and our general response to them.

1. Types of Diesel-Powered Generators

    A commenter questioned whether these generators would be classified 
as heavy-duty diesel-powered equipment. This issue is beyond the scope 
of this rulemaking because it does not address the electrical safety of 
grounding circuits for diesel-powered electrical generators. Examples 
of standards that address the types of diesel generators are Sec.  
75.1908(b) (Nonpermissible diesel-powered equipment; categories) and 
Sec.  72.501 (Emission limits for nonpermissible heavy-duty diesel-
powered equipment, generators, and compressors).

2. Diesel Emissions and Particulates

    Several commenters raised concerns that the proposed rule did not 
address any limits for diesel emissions and particulates emitted into 
the mine atmosphere as a health risk to miners. One commenter stated 
that the proposed rule should include carbon monoxide and nitrogen 
oxide monitoring on the inby equipment operator while the diesel 
generator was used to take equipment in and out of the mine. Another 
commented that the diesel particulate emitted into the mine atmosphere 
is detrimental to miner health. These issues are beyond the scope of 
this rulemaking which addresses the electrical safety of grounding 
circuits for diesel-powered electrical generators. These issues are 
addressed by other standards concerning emissions requirements of 
diesel-powered generators. Mine operators are reminded that they are 
still required to meet the requirements of Sec.  70.1900, (Exhaust Gas 
Monitoring); and Sec.  72.501 (Emission limits for nonpermissible 
heavy-duty diesel-powered equipment, generators and noncompressors).

3. Fire Hazards

    One commenter stated that diesel-powered generators are fire 
hazards and could be placed in areas where smoke could overtake the 
miners. Another commented that diesel-powered generators are a fire 
hazard because the proposed rule failed to require a fire suppression 
system. We disagree with these commenters that the use of diesel-
powered electrical generators is a fire hazard. We have found that any 
previous safety concerns such as explosion, fire, and shock hazards 
initially associated with the use of diesel-powered electrical 
generators have been sufficiently addressed by advances in technology. 
Rather, we recognize that diesel-powered electrical generator equipment 
and circuit design improvements in combination with sensitive 
electrical circuit protections actually reduce fire, explosion, and 
shock hazards. Moreover, during the 13 years these diesel generators 
have been approved through the use of PFM for use in underground mines, 
and we have received no reported incidents of mine fires resulting from 
their use.
    In addition, these issues are beyond the scope of this rulemaking--
electrical safety of grounding circuits for diesel-powered electrical 
generators, and they are addressed by other existing safety standards. 
For example, Sec.  75.380 (Escapeways; bituminous and lignite mines) 
requires two separate and distinct escapeways for miners to escape 
during emergency situations in an underground coal mine, to address any 
smoke hazard. Section 75.1909(j)(3) (Nonpermissible diesel-powered 
equipment; design and performance requirements) requires an automatic 
fire suppression system to address fire hazards. This fire suppression 
system for diesel-powered equipment applies to the diesel-powered 
equipment at issue here. Finally, all other examination requirements in 
30 CFR part 75 for diesel-powered equipment apply.
    In a matter related to fire hazards of diesel-powered generators, 
we received a comment on safe operating temperatures of equipment being 
powered by the diesel generators. This comment is beyond the scope of 
this rulemaking because it does not concern electrical safety of 
grounding circuits for diesel-powered electrical generators and is 
addressed generally by Sec.  75.1725(c) (Machinery and equipment; 
operation and maintenance).

4. Moving Equipment

    A commenter stated that when equipment is being moved in or out of 
the intake escapeway and the equipment breaks down, it blocks the 
intake escapeway, and an emergency vehicle is needed on the outby side 
to transport people in case of an emergency or an accident. This 
comment is beyond the scope of this rulemaking because it does not 
concern electrical safety of grounding circuits for diesel-powered 
electrical generators and is addressed by other existing standards. For 
example, Sec.  75.380 (Escapeways; bituminous and lignite mines), 
requires that escapeways, both primary and alternate, be maintained in 
a travelable condition.

[[Page 77730]]

5. Maintenance of Equipment

    A commenter stated that the diesel-powered generator ``will be 
neglected and cause serious problems just like all the other outby 
equipment.'' This issue concerns every piece of underground equipment 
and not just diesel-powered generators. The comment, therefore, is 
beyond the scope of this rulemaking, because it does not specifically 
concern the electrical safety of grounding circuits for diesel-powered 
electrical generators, and is addressed by other existing standards 
under 30 CFR part 75.

6. Operation of Equipment

    One commenter stated that leaving a piece of diesel-powered 
equipment unattended is unacceptable. We agree with this commenter that 
it is unacceptable to leave diesel-powered equipment unattended. 
Section 75.1916(e) requires diesel-powered equipment not be operated 
unattended. In addition, Sec.  75.1908(c) defines the term 
``attended,'' for diesel-powered equipment (e.g., diesel-powered 
generators). This comment is beyond the scope of this rulemaking 
because it does not specifically concern the electrical safety of 
grounding circuits for diesel-powered electrical generators, and is 
addressed by these existing standards.

7. Petitions for Modification

    One commenter stated that a difference exists between the number of 
PFMs that were granted as shown in the preamble to the proposed rule 
and the number the commenter received under his Freedom of Information 
Act (FOIA) request. We understand that a difference exists between 
these numbers stated in the preamble and the answer to his FOIA 
request. This difference is not significant for the rulemaking because 
we determined the number of petitions for this rulemaking by retrieving 
the files and hand-counted the number of granted PFMs. We stand by the 
number in the proposed rule and the final rule as the number of granted 
PFMs that this rulemaking concerns.

8. Purpose of the Rule

    One commenter stated that it appears that we are more concerned 
about cost savings for the operators than safety for miners. We do not 
agree with this comment. This final rule does not reduce protections 
for miners concerning the use of electrical equipment, e.g., diesel-
powered electrical generators. In fact, this final rule enhances miner 
safety by its required design systems and testing procedures that limit 
the amount of voltage and current to which miners can be exposed under 
ground fault conditions. These enhancements reduce the possibility of 
fire, shock, or burn hazards.
    Furthermore, while this final rule will eliminate the need for 
underground coal mine operators to file PFMs if they choose to use 
diesel-powered electrical generators, it does not reduce protections 
for miners. Some of the protections in this final rule involve the use 
of sensitive ground fault devices in conjunction with a grounding 
resistor that limits the ground fault current to 0.5 amps and trips the 
neutral grounding resistor when a fault current of not more than 90 
milliamps is detected by the system. These requirements reduce the 
potential for shock hazards and prevent the neutral grounding resistor 
from overheating and becoming a fire hazard.

III. Section-by-Section Discussion of the Final Rule

Section 75.901 Protection of Low- and Medium-Voltage Three-Phase 
Circuits Used Underground

    Existing Sec.  75.901contains the requirements for low- and medium-
voltage three-phase alternating-current circuits used underground.
    Final paragraph 75.901(b)(1) through (12) is new and is being added 
to Sec.  75.901 to permit the use of diesel-powered electrical 
generators as an alternative to power centers for the purpose of moving 
equipment in, out, and around the mine, and for performing work in 
areas where permissible equipment is not required. Paragraphs 
75.901(b)(1) through (12) are electrical safety standards applicable to 
low- and medium-voltage diesel-powered electrical generators and 
circuits.
    In the proposed paragraph (b), we inadvertently omitted the word 
``and'' from the phrase ``for the purpose of moving equipment in, out, 
and around the mine,'' in the introductory paragraph for proposed 
paragraphs (b)(1) through (b)(12) as published on June 25, 2004 (69 FR 
35998). The final rule corrects this omission and the final paragraph 
now reads correctly. We did not receive any comments on the proposed 
paragraph. Therefore, paragraph (b) of Sec.  75.901 is finalized as 
corrected.
    Final paragraph (b)(1) requires the diesel engine powering the 
electrical generator to satisfy the requirements of 30 CFR part 7, 
subpart E. The regulations in part 7 set out the requirements for 
diesel engines intended for use in underground coal mines. We did not 
receive any comments on paragraph (b)(1). Therefore, paragraph (b)(1) 
is unchanged from the proposed rule.
    Final paragraph (b)(2) requires a grounding resistor which is rated 
for the phase-to-phase voltage of the system to be provided to limit 
the ground-fault current to not more than 0.5 amperes. To meet these 
requirements, operators must use grounding resistor(s) in one of the 
three methods provided in (b)(2)(i), (ii) and (iii), and as illustrated 
in Appendix A to subpart J. The grounding resistor required by 
(b)(2)(i) must be located between the wye-connected generator neutral 
and the generator frame; or the grounding resistors required by 
(b)(2)(ii) must be located between the wye-connected generator, the 
transformer secondary and the transformer frame, when an isolation 
transformer is used; or the grounding resistor required by (b)(2)(iii) 
must be located between the wye-connected generator neutral and the 
generator frame when an auto-transformer is used.
    Requiring a grounding resistor rated for the phase-to-phase voltage 
of the system will ensure that adequate insulating properties are 
provided for the grounding resistor. This is especially important when 
using auto-transformers. When using an auto-transformer, the grounding 
resistor is 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 auto-transformer. A wye connection 
provides a neutral grounding point in the system for the purpose of 
inserting a predetermined value resistor that would limit the current 
and voltage under a phase-to-ground fault condition. A phase-to-ground 
fault occurring on the secondary side of the auto-transformer would 
subject the grounding resistor to the output voltage of the 
autotransformer. This is because auto-transformers have only one 
winding-per-phase and do not provide the electrical isolation 
characteristics necessary to re-establish a different or new system 
voltage. 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 amperes, and 
providing the sensitive ground-fault protection set forth in paragraphs 
(b)(3) and (b)(4) (discussed below), provides increased protection 
against explosion, fire, and electrical shock. Because the voltage from 
a diesel-powered electrical generator may be increased or decreased by 
an isolation transformer, an

[[Page 77731]]

additional grounding resistor limiting the ground-fault current to 0.5 
amperes would be required. The additional resistor is needed to re-
establish the grounding circuit for the new power circuit derived by 
the isolation characteristics of the transformer.
    For the purpose of establishing an acceptable grounding method for 
(b)(2)(ii) when an isolation transformer is used in conjunction with a 
generator, grounding resistors must be connected between the generator 
wye connection and the generator frame, and between the isolation 
transformer wye connection and the transformer frame.
    The location of the grounding resistor is critical to prevent fire 
and shock hazards. Our experience has shown that the grounding resistor 
has been misplaced in some instances. Final paragraph (b)(2) addresses 
this concern.
    One commenter stated that Sec.  75.901(b)(2), which limits the 
ground fault current to 0.5 amperes, was too restrictive and that the 
requirements for diesel operation should be the same for low- and 
medium-voltage electrical equipment.
    We disagree with the commenter. We acknowledge that under Sec.  
75.901, the present standard for low- and medium-voltage electrical 
equipment typically limits the ground fault current to 15 amps. 
However, when Sec.  75.901 was published in 1970 (35 FR 17890, Nov. 20, 
1970), these sensitive ground fault devices were not available. We have 
chosen to update our electrical standards by requiring the use of these 
sensitive ground-fault devices because the technology permits an 
enhanced level of safety compared with current standards. Also, this 
technology is commercially available and used widely in the mining 
industry and is an approved grounding method under Sec.  75.701.
    Since the mid-1980s, the mining industry has used grounding 
resistors in resistance grounded systems to limit the level of ground 
fault current in a circuit without any reported problems. The use of 
the sensitive ground fault limitation (0.5 amps) and tripping (90 
milliamps) neutral grounding resistor in conjunction with the ground-
fault devices specified in the proposed standard reduces the potential 
for shock hazards and prevents the neutral grounding resistor from 
overheating and becoming a fire hazard.
    Under the granted PFMs, we have required these diesel-powered 
generators to have a resistor that limits the ground fault current to 
0.5 amps and tripping at 90 milliamps. To the best of our knowledge, 
mine operators are able to acquire this technology. In addition, we 
have required that all PFMs granted for high voltage continuous miners, 
high voltage longwalls, and diesel-powered generators have the required 
sensitive ground fault limitation and tripping.
    In addition, the requirements for a sensitive ground fault 
limitation and tripping in neutral grounding systems were included in 
the final rule for the installation, use, and maintenance of high-
voltage longwall mining systems used in underground mines (67 FR 
11002), and it is a requirement in the high-voltage continuous miner 
proposed rule (69 FR 42835). We have evaluated the comment and 
determined that the technology is available, is used by the mining 
industry, provides enhanced safety protection, and does not reduce the 
protections afforded miners under the current standards. Therefore, we 
do not believe that the requirement is too restrictive and the final 
rule retains the proposed language except for the following grammatical 
changes.
    We changed the word ``and'' to ``or'' in subparagraph (b)(2)(i), 
``Between the wye-connected generator neutral and the generator frame; 
(see Figure I in Appendix A to subpart J of this part), as published on 
June 25, 2004 (69 FR 35998) to clarify our intent that three methods 
exists to comply with the requirements in paragraph (b)(2). With this 
change, we are also changing subparagraph (b)(2)(ii) to ``Between the 
wye-connected generator neutral and the generator frame and between the 
wye-connected transformer secondary and the transformer frame when an 
isolation transformer(s) is used and the generator is supplying power 
to other equipment;'' (see Figure II in Appendix A to subpart J of this 
part). These changes are necessary to clarify our intent that two 
resistors are required for isolation transformers as stated in the 
proposed rule and illustrated in the Figure II of the proposed and 
final rules.
    Also, in subparagraphs (b)(2)(i), (ii), and (iii), we added hyphens 
between the words ``wye'' and ``connected'' to clarify modifiers in the 
placement of the grounding resistor as published on June 25, 2004 (69 
FR 35998).
    Paragraph (b)(3) of the final rule requires each three-phase output 
circuit of the generator to be equipped with a sensitive ground fault 
relay set to cause the circuit interrupting device that supplies power 
to the primary windings of each transformer to trip and shut down the 
diesel engine when a phase-to-frame fault of not more than 90 milliamps 
occurs. This maximum current of 90 milliamps reduces the amount of 
voltage to which a miner is exposed under ground fault conditions 
because the miner is in parallel with the grounding circuit conductors. 
When a transformer is used to increase or decrease the voltage provided 
by the diesel-powered generator, the circuit between the generator and 
the transformer would be required to be provided with grounded-phase 
protection. When used in conjunction with the grounding resistor 
required by paragraph (b)(2), the increased protection against 
electrical shock assists in providing a grounding system that satisfies 
the requirements of Sec.  75.701.
    One commenter stated that the requirement for activation of ground 
fault protective devices at 90 milliamps fault current is too 
restrictive. We disagree with the commenter. Our response to this 
comment is the same as our response above in (b)(2). The requirement is 
not too restrictive; the final rule retains the proposed language.
    Final paragraph (b)(4) requires each three-phase output circuit 
that supplies power to equipment have an instantaneous sensitive 
ground-fault relay that will cause its respective circuit interrupting 
device(s) to trip and shutdown the diesel engine when a phase-to-frame 
fault occurs. The rule requires the grounded-phase protection to be set 
at not more than 90 milliamps. This protection would be provided for 
all three-phase equipment circuits. This applies to equipment receiving 
power directly from the diesel-powered electrical generator and from 
transformers used to change the generator voltage. When used in 
conjunction with the grounding resistor(s) addressed in paragraph 
(b)(2), the increased protection against electrical shock provides a 
grounding system that satisfies the requirements of Sec.  75.701.
    The final rule also requires a single window-type current 
transformer to encircle the three-phase conductors for ground-fault 
protection. The equipment safety grounding conductors would be 
prohibited from being passed through or connected in series with the 
ground-fault current transformers. This configuration could defeat the 
ground-fault protection and result in hazardous voltages on equipment 
frames which could potentially cause fatal electrical shocks.
    We did not receive any comments on this proposed paragraph. 
Therefore, paragraph (b)(4) is unchanged from the proposed rule.
    Final paragraph (b)(5) requires each three-phase circuit 
interrupting device to have a means to provide short-circuit, 
overcurrent, grounded-phase, undervoltage, and ground wire monitoring 
protection. When connected

[[Page 77732]]

to a piece of equipment, the instantaneous trip unit for the circuit 
interrupting device must be adjusted to trip at not more than 75 
percent of the minimum available short circuit current at the point 
where the cable enters the equipment or the maximum allowable 
instantaneous settings specified in Sec.  75.601-1, whichever is less. 
To determine the available short circuit current, calculations would be 
required which take into account all circuit parameters, including the 
size and length of the equipment cable. The minimum available short 
circuit current would be at the end of the maximum length cable where 
it enters the equipment. Small capacity generators may cause the 
minimum available short circuit current at the end of the maximum 
length cable to be lower than the maximum allowable settings specified 
in Sec.  75.601-1. These requirements will ensure that proper 
protection is provided for all three-phase output circuits, whether at 
the generator, distribution box, or at a separate power center that 
receives its primary power from a diesel-powered electrical generator. 
We did not receive any comments on the proposed paragraph. Therefore, 
paragraph (b)(5) is unchanged from the proposed rule.
    Final paragraph (b)(6) requires that the equipment portable cable 
length(s) not exceed the length(s) specified in 30 CFR part 18, 
Appendix I, Table 9, Specifications for Portable Cables Longer than 500 
Feet. The purpose of this requirement is to limit the cable length, 
which ensures that the short circuit capacity of the generator is great 
enough to cause the circuit interrupting device to open, thereby 
preventing damage to the cables. We did not receive any comments on the 
proposed paragraph. Therefore, paragraph (b)(6) is unchanged from the 
proposed rule.
    Final paragraph (b)(7) requires that permanent label(s) listing the 
maximum circuit interrupting device setting(s) and maximum portable 
cable length(s) be installed on each instantaneous trip unit or be 
maintained near each three-phase circuit interrupting device. This 
final rule requires that the permanent label(s) be maintained legibly. 
Because the maximum short circuit current is calculated using the 
minimum length cable allowed; the label ensures that adequate short 
circuit protection for each circuit is provided. In addition, other 
existing standards (Sec.  75.601 Short circuit protection of trailing 
cables and Sec.  75.904 Identification of circuit breakers) require the 
circuit breaker, plug, and receptacle to be labeled to identify the 
equipment receiving power.
    We did not receive any comments on the proposed paragraph. 
Therefore, paragraph (b)(7) is unchanged from the proposed rule.
    Final paragraph (b)(8) requires that only one circuit interrupting 
device at a time be used when equipment is being moved in, out, and 
around a mine. This does not prevent the use of more than one circuit 
when equipment is used to perform work in areas where permissible 
equipment is not required. When multiple pieces of equipment are used, 
care must be taken to ensure that the circuit interrupting device 
settings are properly adjusted to protect the generator and the 
equipment being operated.
    We did not receive any comments on the proposed paragraph. However, 
the term ``device'' was inadvertently omitted from the phrase ``circuit 
interrupting device'' in proposed paragraph (b)(8) as published on June 
25, 2004 (69 FR 35998). The final rule corrects this omission and final 
paragraph (b)(8) now reads correctly. Therefore, paragraph (b)(8) is 
finalized as corrected.
    Final paragraph (b)(9) refers to existing Sec.  75.902 (Low- and 
medium-voltage ground check monitor circuits). Section 75.902 requires 
the grounding system to include an MSHA-accepted ground wire monitor 
system, or other no less effective device approved by the Secretary or 
an authorized representative of the Secretary, to assure ground 
continuity between the frame of the generator and the equipment being 
moved or used, or have a No. 1/0 or larger external grounding conductor 
to bond and ground the frames of all equipment to the frame of the 
generator. The final paragraph also requires bonding the frame of 
transformers and metallic cable coupler shells back to the frame of the 
generator. Grounding equipment in this manner limits the amount of 
voltage and current to which a miner would be exposed under an 
electrical fault condition and provides a good path for current flow to 
activate protective devices.
    A commenter stated there was nothing in the standards that requires 
checking for loose ground connections during the shift the generator is 
used. We disagree. The final rule, like the proposed rule, requires the 
use of an MSHA-accepted ground wire monitor system that would detect a 
loose ground and cause the circuit breaker to open the circuit and shut 
down the generator.
    Another commenter stated that an electric shock hazard exists in 
grounding to the frame if the ground wire to the equipment became open. 
We disagree. No hazard exists because the proposed standard requires 
the use of an MSHA-accepted ground wire monitor system that would 
detect an open grounding conductor, cause the circuit breaker supplying 
power to that circuit to open, and shut down the generator.
    Lastly, two commenters stated that while the system is a closed 
circuit system, it is not a grounded system since it is not grounded to 
earth. We recognize that the system is not intentionally connected to 
earth. However, additional safety features have been incorporated, such 
as sensitive ground fault systems and ground wire monitoring that 
provide equivalent protection to assure that the standard would provide 
at least the same measure of protection as the existing standards.
    Based on the above discussion, no changes have been made to 
paragraph (b)(9). Therefore, paragraph (b)(9) is unchanged from the 
proposed rule.
    Final paragraph (b)(10) requires all trailing cables extending from 
the generator to equipment to comply with Sec.  75.907 (Design of 
trailing cables for medium-voltage circuits). Section 75.907 specifies 
the trailing cable design requirements for medium voltage circuits and 
also specifies that on equipment employing cable reels, cables without 
shields may be used if the insulation is rated 2000 volts or more. Both 
type cables have been used in the coal mining industry for over 30 
years and have been proven to provide the required protection when 
properly maintained.
    A commenter recommended revising proposed Sec.  75.901(b)(10) to 
allow the use of un-shielded trailing cables from the generator to 
supply approved low voltage permissible pumps because the packing 
glands the pumps were approved with would not accommodate the shielded 
cables. The final rule, as well as the proposed rule, does not permit 
diesel-powered electric generators to be used where permissible 
equipment is required. To do so could reduce the protections afforded 
miners under the current standards. Therefore, paragraph (b)(10) is 
unchanged from the proposed rule.
    Final paragraph (b)(11) requires a strain relief device on each end 
of the trailing cable(s) that extends between the generator and the 
piece of equipment being powered. Although requirements for strain 
relief or clamping of cables are covered by other standards, they are 
specifically required here because the cables are likely to be pulled 
to the extent of their length during movement of equipment. This final 
paragraph also applies to the cable(s) between the diesel-powered

[[Page 77733]]

generator, transformer, distribution box and equipment. Some mobile 
equipment may be capable of pulling the distribution box when the limit 
of the cable has been reached and further pulling would strain 
connections of the generator cable. This could result in electrical 
arcs and faults which may result in flash burns, or fire. We did not 
receive any comments on this proposed paragraph. Therefore, paragraph 
(b)(11) of Sec.  75.901 is unchanged from the proposed rule.
    Final paragraph (b)(12) requires that, prior to moving each piece 
of equipment or performing work, a functional test of each ground fault 
and ground wire monitor system be performed by a qualified electrician 
who meets the requirements of Sec.  75.153 (Electrical work; qualified 
person). The ground-fault circuit is tested without subjecting the 
circuit to an actual grounded phase condition. This paragraph requires 
a record of each test to be maintained by the mine operator and made 
available to authorized representatives of the Secretary and to the 
miners in the mine. This paragraph requires that functional tests be 
performed before the equipment begins its move from the surface to 
underground, and from underground to the surface, and movement from one 
area of a mine to another, and before work is performed by equipment in 
other areas of the mine where permissible equipment is not required. It 
does not require a functional test after momentary or incidental 
stoppage during the moving process, or repositioning of equipment while 
performing work. Manufacturers of ground fault relay devices already 
provide circuitry and test methods for their devices that allow testing 
to be conducted without subjecting the power system to an actual ground 
fault condition. This method of testing enhances safety by preventing 
miners from being exposed to energized circuits while performing the 
test. The functional tests required by this paragraph do not relieve 
the mine operator of responsibility for performing examinations and 
tests required by other sections of 30 CFR part 75.
    Two commenters stated that a functional test as required by Sec.  
75.901(b)(12) would be necessary only at the start of each project even 
if there was a shift or multiple shifts break before starting to use 
the generator again and would be no different than a momentary 
stoppage. They further stated that the generator will be checked on a 
weekly basis and required to be maintained in a safe operating 
condition. Therefore, they commented that we should change the 
paragraph to require a functional test at the start of each project.
    We disagree with these comments. Testing the protective devices 
prior to moving equipment, except for momentary stoppages, ensures that 
the devices are functioning properly. If the movement of the equipment 
is halted for a period of time (multiple shifts), the project has 
stopped and the protective devices should be tested again when the 
project is resumed. These tests take a minimal amount of time to 
conduct (minutes) and delays are negligible when compared to the shifts 
or days that the equipment has been idled. This requirement assures 
that any problems, e.g., loose grounding wire, which may arise during 
movement or stoppage will be identified and corrected so that miners 
are not exposed to hazards.
    Further, paragraph (b)(2) updates the electrical requirements by 
providing these protective devices to provide an enhanced level of 
safety. As part of our longstanding policy to require these sensitive 
ground-fault devices, we have included requirements to use the 
manufacturers' installed test equipment each time these devices are 
activated prior to movement of equipment or performing work. Reducing 
the number of functional tests would reduce the protections afforded 
miners under the current standards.
    For these reasons, we made no changes to paragraph (b)(12) and the 
paragraph is unchanged from the proposed rule.
    Appendix A to subpart J consists of three figures applicable to 
Sec.  75.901(b)(2)(i), (ii) and (iii). Figure I, applicable to Sec.  
75.901(b)(2)(i), shows the neutral grounding resistor connected between 
the wye-connected generator neutral and the generator frame; Figure II, 
applicable to Sec.  75.901(b)(2)(ii), shows the neutral grounding 
resistors connected between the wye-connected generator and the 
transformer secondary and the transformer frame when an isolation 
transformer is used. We did not receive any comments on Figures I and 
II in the proposed appendix; therefore, Figures I and II in Appendix A 
to subpart J are unchanged from the proposed rule. Figure III, 
applicable to Sec.  75.901(b)(iii), shows the neutral grounding 
resistor connected between the wye-connected generator neutral and the 
generator frame when an auto-transformer is used. We discovered an 
error in Figure III, in Appendix A to Subpart J, after the proposed 
rule was published in the Federal Register. However, this final rule 
corrects the error and Figure III is correct. We did not receive any 
comments on proposed Figure III and therefore, Figure III in Appendix A 
to Subpart J is finalized as corrected.

IV. Executive Order 12866 (Regulatory Planning and Review and 
Regulatory Flexibility Act)

    Executive Order (E.O.) 12866 as amended by E.O. 13258 requires that 
regulatory agencies assess both the costs and benefits of intended 
regulations. We have fulfilled this requirement for the final rule, and 
have determined that the final rule will not have an annual effect of 
$100 million or more on the economy. Therefore, it is not an 
economically significant regulatory action pursuant to section 3(f)(1) 
of E.O. 12866.
    The final rule will eliminate the need for underground coal mine 
operators who choose to use diesel-powered electrical generators to 
file PFMs and thereby will generate cost savings.
    From January 1990 to October 2003, 63 petitions were filed to 
modify Sec. Sec.  75.701 and 75.901 (Grounding requirements and 
protection of low- and medium-voltage three-phase circuits used 
underground). On average, approximately five petitions were filed 
during each of these years.

Mining Sectors Affected

    This final rule applies to all underground coal mines. However, 
based on already filed PFMs under Sec.  75.901 and Sec.  75.701, we 
estimate that an average of five underground coal mines per year would 
choose to use diesel-powered electrical generators in their mines.

Benefits

    Diesel-powered electrical generators provide an efficient portable 
source of power to move electrical equipment. These diesel-powered 
electrical generators are easily taken to areas where power centers or 
other sources of electrical power are not available to move mobile 
equipment or to supply power to other electrical equipment needed to do 
work in outby areas. The likelihood of electrical accidents will be 
decreased by (1) the protective design features associated with the 
diesel-powered electrical generator protective devices, such as 
requiring the grounding resistor to limit ground fault current to 0.5 
amperes under a ground fault condition; (2) requiring the sensitive 
grounded phase protection device to cause the circuit interrupting 
device protecting the electrical circuits to open and shut down the 
diesel-powered generator when a fault current of not more than 90 
milliamperes is detected by the system; and (3) equipment testing 
devices and procedures that are

[[Page 77734]]

designed to facilitate safe testing of the diesel-powered electrical 
circuit. Miner safety is increased with the protective systems and 
testing procedures required by the rule because they limit the amount 
of voltage and current that miners can be exposed to under a ground 
fault condition and also because they reduce the possibility of a fire, 
shock, or burn hazard. Finally, the rule contains all the necessary 
electrical safety requirements developed in the PFMs to use diesel-
powered electrical generators.

Compliance Cost Savings

    Annual cost savings from the final rule will accrue to underground 
coal mine operators who choose to use diesel-powered electrical 
generators because they will no longer have to file an average of five 
PFMs per year. We project that all five affected mines will employ 
between 20 to 500 workers.
    The annual cost savings were derived by using the following: a mine 
supervisor, earning $57.70 per hour, taking 8 hours to prepare a 
petition; a clerical worker earning $21.82 per hour taking 0.1 hours to 
copy and mail a petition; photocopying five pages per petition at a 
cost of $0.15 per page; and postage of $1 to send the petition to MSHA. 
Based on the above, underground coal mine operators will incur cost 
savings of $2,328. These savings are derived as follows:

5 petitions x 8.0 hrs. x $57.70 per hr................    =       $2,308
5 petitions x 0.1 hrs. x $21.82 per hr................    =          $11
5 petitions x (($0.15 photocopy cost per page x 5         =           $9
 pages) + $1 postage per petition)....................
                                                            ------------
                                                          =       $2,328
 

    There are no substantive changes in the final rule that apply to 
underground coal mines that choose not to use diesel-powered electrical 
generators. Thus, such mines will not incur costs nor generate cost 
savings as a result of the final rule.

Feasibility

    MSHA has concluded that the requirements of the proposed rule are 
both technologically and economically feasible.
    This final rule is not a technology-forcing standard and does not 
involve activities on the frontiers of scientific knowledge. The 
requirements of this rulemaking are based on the terms and conditions 
in granted petitions.
    This rulemaking provides an annual cost savings of $2,328 to 
underground coal and metal and nonmetal mine operators whose yearly 
revenues are in the billions of dollars.

V. Regulatory Flexibility Act Certification

    Pursuant to the Regulatory Flexibility Act (RFA) of 1980 as amended 
by the Small Business Regulatory Enforcement Fairness Act (SBREFA), we 
have analyzed the impact of the final rule on small businesses. 
Further, we have made a determination with respect to whether or not we 
can certify that the final rule will not have a significant economic 
impact on a substantial number of small entities that are covered by 
this rulemaking. Under the SBREFA amendments to the RFA, we must 
include in the rule a factual basis for this certification. If the 
final rule will have a significant economic impact on a substantial 
number of small entities, we must develop a regulatory flexibility 
analysis.

Definition of a Small Mine

    Under the RFA, in analyzing the impact of a rule on small entities, 
we must use the SBA definition for a small entity or, after 
consultation with the SBA Office of Advocacy, establish an alternative 
definition for the mining industry by publishing that definition in the 
Federal Register for notice and comment. We have not taken such an 
action and hence are required to use the SBA definition.
    The SBA defines a small entity in the mining industry as an 
establishment with 500 or fewer employees. All mines affected by this 
rulemaking fall into this category and hence can be viewed as sharing 
the special regulatory concerns which the RFA was designed to address.
    We have looked at the impacts of our rules on a subset of mines 
with 500 or fewer employees--those with fewer than 20 employees, which 
we and the mining community have traditionally referred to as ``small 
mines.'' These small mines differ from larger mines not only in the 
number of employees, but also in economies of scale in material 
produced, in the type and amount of production equipment, and in supply 
inventory. Therefore, their costs of complying with MSHA rules and the 
impact of MSHA rules on them will also tend to be different. It is for 
this reason that ``small mines,'' as traditionally defined by MSHA, are 
of special concern to us.
    This analysis complies with the legal requirements of the RFA for 
an analysis of the impacts on ``small entities'' while continuing our 
traditional definition of ``small mines.'' We conclude that we can 
certify that the final rule will not have a significant economic impact 
on a substantial number of small entities that are covered by this 
rulemaking. We have determined that this is the case both for mines 
affected by this rulemaking with fewer than 20 employees and for mines 
affected by this rulemaking with 500 or fewer employees.

Factual Basis for Certification

    Our analysis of impacts on ``small entities'' begins with a 
``screening'' analysis. The screening compares the estimated compliance 
costs of a rule for small entities in the sector affected by the rule 
to the estimated revenues for those small entities. When estimated 
compliance costs are less than one percent of the estimated revenues or 
are negative (i.e., cost savings) we believe it is generally 
appropriate to conclude that there is no significant economic impact on 
a substantial number of small entities. When estimated compliance costs 
exceed one percent of revenues, it tends to indicate that further 
analysis may be warranted. Since underground coal mine operators 
employing fewer than 20 workers have not filed for a petition to use 
low- and medium-voltage diesel-powered electrical generators, we do not 
expect the final rule to have any impact on them. Therefore, the 
analysis of the final rule on small entities is based only on SBA's 
small mine definition (those having 500 or fewer employees). Using 
SBA's definition of a small mine (those having 500 or fewer employees) 
the final rule results in cost savings of $2,328. We therefore conclude 
that the final rule will not have a significant economic impact on a 
substantial number of small entities.

VI. Paperwork Reduction Act of 1995

    The amendments to Sec.  75.901 do not introduce new paperwork 
requirements on the mine operator; however, the existing information 
collection requirements are still subject to Office of Management and 
Budget (OMB) approval under the Paperwork

[[Page 77735]]

Reduction Act (PRA), 44 U.S.C. 3502(13)(A). As a result of this rule, 
all PFMs for Sec.  75.901 will be superseded, and the information 
collection request for petitions for modification approved by OMB under 
1219-0065 will be reduced. We will submit to OMB a new information 
collection request for this rule and transfer the recordkeeping 
paperwork burden hours and costs.

Burden Reduction

    Due to this rulemaking, mine operators will no longer have to 
petition for modification of existing Sec.  75.901 in order to use 
diesel-powered electrical generators. Existing OMB paperwork package 
1219-0065 includes annual burden hours and costs related to the time it 
takes mine operators to prepare and file petitions with us, including 
petitions for modifications to use diesel-powered generators. As a 
result of this rulemaking, the burden hours and costs in OMB paperwork 
package 1219-0065 that relate to the time it takes operators to prepare 
and file petitions will need to be reduced to reflect the fact that 
PFMs to use diesel-powered electrical generators will no longer be 
needed. Therefore, the burden hours and costs in OMB paperwork package 
1219-0065 should be reduced by 40.5 hours and $2,328 annually. This 
reduction was derived in the following manner.
    On average, five underground coal mines are estimated to begin to 
use diesel-powered electrical generators annually. A mine supervisor, 
earning $57.70 per hour, is estimated to take 8 hours to prepare a 
petition. On average, a clerical worker, earning $21.82 per hour, is 
estimated to take 0.1 hours to copy and mail a petition. Each petition 
is estimated to be five pages in length, photocopy costs are $0.15 per 
page, and postage is $1 for each petition. The annual burden hour 
reduction and cost savings related to preparing and filing petitions 
are:

Burden Hour Reduction:
    5 petitions x 8 hrs. per petition............    =        40.0 hours
    5 petitions x 0.1 hrs. per petition..........    =         0.5 hours
                                                       -----------------
                                                     =        40.5 hours
Burden Cost Savings:
    40 hours x $57.70 wage per hr................    =            $2,308
    0.5 hrs. x $21.82 wage per hr................    =               $11
    5 petitions x ((5 pgs. x $0.15 per page) +       =                $9
     ($1 postage)................................
                                                       -----------------
                                                     =            $2,328
 

Burden Transfer

    Also included in existing PFMs of Sec.  75.901 to use diesel-
powered electrical generators are operators' recordkeeping requirements 
related to performing ground fault and ground wire monitor system tests 
and making a record of these tests. Such tests must be conducted and 
records made prior to moving each piece of equipment or performing 
work. The burden hours and costs related to such tests and records are 
also included in OMB paperwork package 1219-0065. There are 38 burden 
hours and $1,064 of burden costs in the first year, 42 burden hours and 
$1,176 of burden costs in the second year, and 46 burden hours and 
$1,289 of burden costs in the third year that would be related to these 
tests and records which would need to be removed from OMB paperwork 
package 1219-0065 and transferred to the paperwork package related to 
this rule. The burden hours and costs were derived as follows.
    There were 16 mines operating in 2003 that have petitions to use 
diesel-powered electrical generators. We assume that although five 
mines annually are estimated to begin using diesel-powered generators, 
there would, on average, be three existing mines using such equipment 
that would close. Thus, each year there would be a net of two more 
mines using diesel-powered electrical generators. A mine electrician 
earning $28.01 per hour, is estimated to take 0.25 hours to perform the 
ground fault and ground wire monitor system tests. Such tests are 
estimated to be conducted six times annually. On average, it is 
estimated to take the mine electrician 0.1 hours to make a record each 
time tests are conducted.
    The first year burden hours and costs related to performing ground 
fault and ground wire monitor system tests and making a record are:

18 mines x (0.25 hrs. + 0.1 hrs. for tests and record) x 6 times per 
year = 38 hours
38 hours x $28.01 wage per hour = $1,064

    The second year burden hours and costs related to performing ground 
fault and ground wire monitor system tests and making a record are:

20 mines x (0.25 hrs. + 0.1 hrs. for tests and record) x 6 times per 
year = 42 hours
42 hours x $28.01 wage per hr. = $1,176

    The third year burden hours and costs related to performing ground 
fault and ground wire monitor system tests and making a record are:

22 mines x (0.25 hrs. + 0.1 hrs. for tests and record) x 6 times per 
year = 46 hours.
46 hours x $28.01 wage per hr. = $1,289

VII. Other Regulatory Considerations

A. The Unfunded Mandates Reform Act

    This final rule does not include any Federal mandate that may 
result in increased expenditures by State, local, or tribal 
governments; nor does it increase private sector expenditures by more 
than $100 million annually; nor does it significantly or uniquely 
affect small governments. Accordingly, the Unfunded Mandates Reform Act 
of 1995 (2 U.S.C. 1501 et seq.) requires no further agency action or 
analysis.

B. The Treasury and General Government Appropriations Act of 1999: 
Assessment of Federal Regulations and Policies on Families

    This final rule has no affect on family well-being or stability, 
marital commitment, parental rights or authority, or income or poverty 
of families and children. Accordingly, section 654 of the Treasury and 
General Government Appropriations Act of 1999 (5 U.S.C. 601 note) 
requires no further agency action, analysis, or assessment.

C. Executive Order 12630: Government Actions and Interference With 
Constitutionally Protected Property Rights

    This final rule does not implement a policy with takings 
implications. Accordingly, Executive Order 12630, Governmental Actions 
and Interference with Constitutionally Protected Property Rights, 
requires no further agency action or analysis.

D. Executive Order 12988: Civil Justice Reform

    This final rule was written to provide a clear legal standard for 
affected

[[Page 77736]]

conduct and was carefully reviewed to eliminate drafting errors and 
ambiguities, so as to minimize litigation and undue burden on the 
Federal court system. Accordingly, this final rule meets the applicable 
standards provided in section 3 of Executive Order 12988, Civil Justice 
Reform.

E. Executive Order 13045: Protection of Children From Environmental 
Health Risks and Safety Risks

    This final rule has no adverse impact on children. Accordingly, 
Executive Order 13045, Protection of Children from Environmental Health 
Risks and Safety Risks, as amended by Executive Orders 13229 and 13296, 
requires no further agency action or analysis.

F. Executive Order 13132: Federalism

    This final rule does not have ``federalism implications,'' because 
it does not ``have substantial direct effects on the States, on the 
relationship between the national government and the States, or on the 
distribution of power and responsibilities among the various levels of 
government.'' Accordingly, Executive Order 13132, Federalism, requires 
no further agency action or analysis.

G. Executive Order 13175: Consultation and Coordination With Indian 
Tribal Governments

    This final rule does not have ``tribal implications,'' because it 
does not ``have substantial direct effects on one or more Indian 
tribes, on the relationship between the Federal government and Indian 
tribes, or on the distribution of power and responsibilities between 
the Federal government and Indian tribes.'' Accordingly, Executive 
Order 13175, Consultation and Coordination with Indian Tribal 
Governments, requires no further agency action or analysis.

H. Executive Order 13211: Actions Concerning Regulations That 
Significantly Affect Energy, Supply, Distribution, or Use

    We have reviewed this final rule for its impact on the supply, 
distribution, and use of energy because it applies to the underground 
coal mining sector. Because this final rule will result in yearly cost 
savings to the coal mining industry, this final rule will neither 
reduce the supply of coal nor increase its price.
    This final rule is not a ``significantly energy action,'' because 
it is not ``likely to have a significant adverse effect on the supply, 
distribution, or use of energy (including a shortfall in supply, price 
increases, and increased use of foreign supplies). Accordingly, 
Executive Order 13211, Actions Concerning Regulations That 
Significantly Affect Energy Supply, Distribution, or Use, requires no 
further agency action or analysis.''

I. Executive Order 13272: Proper Consideration of Small Entities in 
Agency Rulemaking

    We have thoroughly reviewed this final rule to assess and take 
appropriate account of its potential impact on small businesses, small 
governmental jurisdictions, and small organizations. We have determined 
and certified that this final rule will not have a significant economic 
impact on a substantial number of small entities. We solicited public 
comments concerning the accuracy and completeness of this potential 
impact when the rule was proposed. We took appropriate account of 
comments received relevant to the rule's potential impact on small 
entities. Accordingly, Executive Order 13272, Proper Consideration of 
Small Entities in Agency Rulemaking, requires no further action or 
analysis by us.

VIII. Petitions for Modification

    On the effective date of this final rule, all existing PFMs for 
diesel-powered electrical generators granted under Sec.  75.901 and/or 
Sec.  75.701 will be superseded.

List of Subjects in 30 CFR Part 75

    Mine safety and health, Underground coal mining.

    Dated: December 23, 2005.
David G. Dye,
Acting Assistant Secretary of Labor for Mine Safety and Health.

0
For the reasons set out in the preamble, and under the authority of the 
Federal Mine Safety and Health Act of 1977, we are amending chapter I, 
subchapter O, part 75 of title 30 of the Code of Federal Regulations as 
follows:

PART 75--MANDATORY SAFETY STANDARDS--UNDERGROUND COAL MINES

0
1. The authority citation for part 75 continues to read as follows:

    Authority: 30 U.S.C. 811.

SUBCHAPTER O--[AMENDED]

0
2. Section 75.901 is amended by adding paragraph (b) to read as 
follows:


Sec.  75.901  Protection of low- and medium-voltage three-phase 
circuits used underground.

* * * * *
    (b) Diesel-powered electrical generators used as an alternative to 
power centers for the purpose of moving equipment in, out, and around 
the mine, and to perform work in areas where permissible equipment is 
not required, must comply with the following:
    (1) The diesel engine powering the electrical generator must be 
approved under 30 CFR part 7, subpart E.
    (2) A grounding resistor rated for the phase-to-phase voltage of 
the system must be provided to limit the ground-fault current to not 
more than 0.5 amperes. The grounding resistor(s) must be located:
    (i) Between the wye-connected generator neutral and the generator 
frame; (see Figure I in Appendix A to subpart J of this part) or
    (ii) Between the wye-connected generator neutral and the generator 
frame and between the wye-connected transformer secondary and the 
transformer frame when an isolation transformer(s) is used and the 
generator is supplying power to the other equipment; (see Figure II in 
Appendix A to subpart J of this part) or
    (iii) Between the wye-connected generator neutral and the generator 
frame when an auto-transformer is used. (see Figure III in Appendix A 
to subpart J of this part)
    (3) Each three-phase output circuit of the generator must be 
equipped with a sensitive ground fault relay. The protective relay must 
be set to cause the circuit interrupting device that supplies power to 
the primary windings of each transformer to trip and shut down the 
diesel engine when a phase-to-frame fault of not more than 90 
milliamperes occurs.
    (4) Each three-phase output circuit that supplies power to 
equipment must be equipped with an instantaneous sensitive ground-fault 
relay that will cause its respective circuit interrupting device(s) to 
trip and cause shutdown of the diesel engine when a phase-to-frame 
fault occurs. The grounded-phase protection must be set at not more 
than 90 milliamps. Current transformers used for the ground-fault 
protection must be single window-type and must be installed to encircle 
all three phase conductors. Equipment safety grounding conductors must 
not pass through or be connected in series with ground-fault current 
transformers.
    (5) Each three-phase circuit interrupting device must be provided 
with a means to provide short-circuit, overcurrent, grounded-phase, 
undervoltage, and ground wire monitoring protection. The instantaneous 
only trip unit for the circuit interrupting device(s) in use must be 
adjusted to trip at not more than 75 percent of the minimum available 
short circuit current at the

[[Page 77737]]

point where the portable cable enters the equipment or the maximum 
allowable instantaneous settings specified in Sec.  75.601-1, whichever 
is less.
    (6) The equipment portable cable length(s) must not exceed the 
length(s) specified in 30 CFR part 18, appendix I, table 9, 
Specifications for Cables Longer than 500 Feet.
    (7) Permanent label(s) listing the maximum circuit interrupting 
device setting(s) and maximum portable cable length(s) must be 
installed on each instantaneous trip unit or be maintained near each 
three-phase circuit interrupting device. The permanent label(s) must be 
maintained legibly.
    (8) The circuit interrupting device that supplies three-phase power 
circuit(s) to the equipment being powered must be limited to the use of 
only one circuit interrupting device at a time when equipment is being 
moved in, out, and around the mine.
    (9) The grounding system must include an MSHA-accepted ground wire 
monitor system that satisfies the requirements of Sec.  75.902; or have 
a No. 1/0 or larger external grounding conductor to bond and ground the 
frames of all equipment to the f