Low- and Medium-Voltage Diesel-Powered Electrical Generators
[12/30/2005]
Volume 70, Number 250, Page 77728-77739
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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 http://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 frame of the generator.
(10) All trailing cables extending from the generator to equipment
must comply with Sec. 75.907.
(11) A strain relief device must be provided on each end of the
trailing cables that extends between the generator and the piece of
equipment being powered.
(12) Prior to moving each piece of equipment or performing work, a
functional test of each ground fault and ground wire monitor system
must be performed by a qualified electrician who meets the requirements
of Sec. 75.153. The ground-fault circuit must be tested without
subjecting the circuit to an actual grounded phase condition. A record
of each test must be maintained and made available to authorized
representatives of the Secretary and to the miners in such mine.
0
3. Appendix A to subpart J is added to read as follows:
BILLING CODE 4510-43-P
[GRAPHIC] [TIFF OMITTED] TR30DE05.146
[[Page 77738]]
[GRAPHIC] [TIFF OMITTED] TR30DE05.147
[[Page 77739]]
[GRAPHIC] [TIFF OMITTED] TR30DE05.148
[FR Doc. 05-24625 Filed 12-29-05; 8:45 am]
BILLING CODE 4510-43-C
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