§ 868. — Underground highvoltage distribution.
[Laws in effect as of January 24, 2002]
[Document not affected by Public Laws enacted between
January 24, 2002 and December 19, 2002]
[CITE: 30USC868]
TITLE 30--MINERAL LANDS AND MINING
CHAPTER 22--MINE SAFETY AND HEALTH
SUBCHAPTER III--INTERIM MANDATORY SAFETY STANDARDS FOR UNDERGROUND COAL
MINES
Sec. 868. Underground high-voltage distribution
(a) Circuits entering underground areas of mines; circuit breakers
High-voltage circuits entering the underground area of any coal mine
shall be protected by suitable circuit breakers of adequate interrupting
capacity which are properly tested and maintained as prescribed by the
Secretary. Such breakers shall be equipped with devices to provide
protection against under-voltage, grounded phase, short circuit, and
overcurrent.
(b) Circuits extending underground and supplying equipment; direct
neutral grounds; ground conductors for frames, exceptions;
location of disconnection devices, exceptions
High-voltage circuits extending underground and supplying portable,
mobile, or stationary high-voltage equipment shall contain either a
direct or derived neutral which shall be grounded through a suitable
resistor at the source transformers, and a grounding circuit,
originating at the grounded side of the grounding resistor, shall extend
along with the power conductors and serve as a grounding conductor for
the frames of all high-voltage equipment supplied power from that
circuit, except that the Secretary or his authorized representative may
permit ungrounded high-voltage circuits to be extended underground to
feed stationary electrical equipment if such circuits are either steel
armored or installed in grounded, rigid steel conduit throughout their
entire length, and upon his finding that such exception does not pose a
hazard to the miners. Within one hundred feet of the point on the
surface where high-voltage circuits enter the underground portion of the
mine, disconnecting devices shall be installed and so equipped or
designed in such a manner that it can be determined by visual
observation that the power is disconnected, except that the Secretary or
his authorized representative may permit such devices to be installed at
a greater distance from such area of the mine if he determines, based on
existing physical conditions, that such installation will be more
accessible at a greater distance and will not pose any hazard to the
miners.
(c) Grounding resistors
The grounding resistor, where required, shall be of the proper ohmic
value to limit the voltage drop in the grounding circuit external to the
resistor to not more than 100 volts under fault conditions. The
grounding resistor shall be rated for maximum fault current continuously
and insulated from ground for a voltage equal to the phase-to-phase
voltage of the system.
(d) Inclusion of fail safe ground check circuits in resistance grounded
systems; operative functions; time extension
Six months after the operative date of this subchapter, high-
voltage, resistance grounded systems shall include a fail safe ground
check circuit to monitor continuously the grounding circuit to assure
continuity and the fail safe ground check circuit shall cause the
circuit breaker to open when either the ground or pilot check wire is
broken, or other no less effective device approved by the Secretary or
his authorized representative to assure such continuity, except that an
extension of time, not in excess of twelve months, may be permitted by
the Secretary on a mine-by-mine basis if he determines that such
equipment is not available.
(e) Underground cables used in resistance grounded systems; metallic
shields for power conductors; standards; splices
(1) Underground high-voltage cables used in resistance grounded
systems shall be equipped with metallic shields around each power
conductor, with one or more ground conductors having a total cross-
sectional area of not less than one-half the power conductor, and with
an insulated internal or external conductor not smaller than No. 8 (AWG)
for the ground continuity check circuit.
(2) All such cables shall be adequate for the intended current and
voltage. Splices made in such cables shall provide continuity of all
components.
(f) Couplers for power circuits; guidelines for construction
Couplers that are used with medium-voltage or high-voltage power
circuits shall be of the three-phase type with a full metallic shell,
except that the Secretary may permit, under such guidelines as he may
prescribe, no less effective couplers constructed of materials other
than metal. Couplers shall be adequate for the voltage and current
expected. All exposed metal on the metallic couplers shall be grounded
to the ground conductor in the cable. The coupler shall be constructed
so that the ground check continuity conductor shall be broken first and
the ground conductors shall be broken last when the coupler is being
uncoupled.
(g) Connections of single-phase loads
Single-phase loads, such as transformer primaries, shall be
connected phase to phase.
(h) Installation of underground transmission cables
All underground high-voltage transmission cables shall be installed
only in regularly inspected air courses and haulageways, and shall be
covered, buried, or placed so as to afford protection against damage,
guarded where men regularly work or pass under them unless they are six
and one-half feet or more above the floor or rail, securely anchored,
properly insulated, and guarded at ends, and covered, insulated, or
placed to prevent contact with trolley wires and other low-voltage
circuits.
(i) Disconnection devices; location; visual observation of position of
switch
Disconnecting devices shall be installed at the beginning of branch
lines in high-voltage circuits and equipped or designed in such a manner
that it can be determined by visual observation that the circuit is
deenergized when the switches are open.
(j) Circuit breakers and disconnection devices; markings
Circuit breakers and disconnecting switches underground shall be
marked for identification.
(k) Splices in cables used as trailing cables; terminations and splices
in other cables
In the case of high-voltage cables used as trailing cables,
temporary splices shall not be used and all permanent splices shall be
made in accordance with section 866(e) of this title. Terminations and
splices in all other high-voltage cables shall be made in accordance
with the manufacturer's specifications.
(l) Grounding of frames of underground equipment
Frames, supporting structures, and enclosures of stationary,
portable, or mobile underground high-voltage equipment and all high-
voltage equipment supplying power to such equipment receiving power from
resistance grounded systems shall be effectively grounded to the high-
voltage ground.
(m) Moving of power centers, transformers, and cables; deenergizing;
exceptions; safety guidelines; record of examinations
Power centers and portable transformers shall be deenergized before
they are moved from one location to another, except that, when equipment
powered by sources other than such centers or transformers is not
available, the Secretary may permit such centers and transformers to be
moved while energized, if he determines that another equivalent or
greater hazard may otherwise be created, and if they are moved under the
supervision of a qualified person, and if such centers and transformers
are examined prior to such movement by such person and found to be
grounded by methods approved by an authorized representative of the
Secretary and otherwise protected from hazards to the miner. A record
shall be kept of such examinations. High-voltage cables, other than
trailing cables, shall not be moved or handled at any time while
energized, except that, when such centers and transformers are moved
while energized as permitted under this subsection, energized high-
voltage cables attached to such centers and transformers may be moved
only by a qualified person and the operator of such mine shall require
that such person wear approved and tested insulated wireman's gloves.
(Pub. L. 91-173, title III, Sec. 308, Dec. 30, 1969, 83 Stat. 780.)
References in Text
For the operative date of this subchapter, referred to in subsec.
(d), see section 509 of Pub. L. 91-173, set out as an Effective Date
note under section 801 of this title.
Section Referred to in Other Sections
This section is referred to in section 861 of this title.
