Program Policy Manual - VOLUME V - Mine Safety and Health ...

MSHA PROGRAM POLICY MANUAL VOLUME V
Subpart G Trailing Cables
77.600 Trailing Cables; Short-Circuit Protection;
Disconnecting Devices
This Section does not permit the use of single element fuses
for trailing cable short-circuit protection. Dual element
fuses with adequate interrupting capacity may be used to
provide short circuit protection for single phase and d.c.
trailing cable circuits.
"Adequate interrupting capacity" means that the fuse or
circuit breaker is capable of interrupting the maximum shortcircuit
current the circuit may conduct without destruction
to the device.
This Section requires that short-circuit protection be
provided for each undergrounded power conductor. Therefore,
in direct current systems in which neither polarity is
grounded, protective elements shall be provided for both the
positive and negative lines. This necessitates the use of
either a fuse in each polarity or a two-pole circuit breaker.
A visual means of disconnecting power from trailing cables
must be provided so that it can readily be determined whether
or not the cable is deenergized. Enclosed circuit breakers
are not acceptable as visual evidence that power is
disconnected. Plugs and receptacles located at the circuit
breaker would be acceptable as the visible means of
disconnecting the power.
77.603 Clamping of Trailing Cables to Equipment
If a strain clamp is used, it shall be designed and installed
to prevent damage to the cable jacket. Cable grips, such as
Kellems grips, anchored to the machine, may be used in lieu
of strain clamps.
77.606 Energized Trailing Cables; Handling
Other protective devices such as insulated sleeves, insulated
jackets, insulated aprons, insulated cable handling hooks,
etc., are required by this Section when they are necessary to
prevent the energized trailing cable from contacting the
cable handler's body or clothing.
77.606-1 Rubber Gloves; Minimum Requirements
Rubber gloves with a rating of at least 20,000 volts shall be
worn while handling energized high-voltage trailing cables,
regardless of what other protective devices are used.
February 2003 (Release V-33)
183