West Virginia Code of State Rules › Agency 36 - Coal Mine Health And Safety › Title 36 - LEGISLATIVE EXEMPT RULE BOARD OF COAL MINE HEALTH AND SAFETY › Series 36-48 - Rules And Regulations Governing High Voltage Continuous Miners › Section 36-48-3 - High Voltage Protection

Current through Register Vol. XLI, No. 28, July 12, 2024
3.1. The
				nominal voltage of power circuits shall not exceed 2,400 volts.
3.2. The nominal voltage of the control
				circuits shall not exceed 120 volts.
3.3. The ground-fault current shall be
				limited by a neutral grounding resistor to not more than 0.5 ampere. Current
				transformers used for the ground-fault protection shall be the single-window
				type and shall be installed to encircle all three-phase conductors.
3.4. The trailing cable for the 2,400-volt
				continuous miner circuit shall be provided with instantaneous ground-fault
				protection set at not more than 0.125 ampere. The ground-fault protection
				device shall be equipped with an impedance measuring feature, "Look-Ahead"
				circuit, to guard against closing the circuit breaker on a circuit that has an
				existing ground-fault condition.
3.5. The neutral grounding resistor shall be
				provided with backup ground fault protection that will de-energize the primary
				of the transformer if a ground fault occurs with the neutral grounding resistor
				open. This protection shall be set at 40% of the maximum voltage that could
				appear across the neutral grounding resistor during a ground fault. A time
				delay set at the lowest practical value that permits reliable coordination
				shall be permitted. The time delay shall not exceed 0.250 second.
3.6. The neutral grounding resistor for the
				transformer supplying power to the 2,400-volt continuous miner shall be
				provided with thermal protection that will de-energize the incoming
				high-voltage circuit supplying power to the power center if the grounding
				resistor is subjected to a sustained ground-fault. The thermal protection shall
				operate at either 50 percent of the maximum temperature rise of the grounding
				resistor, or 1500 C (3020
				F), whichever is less. The thermal protection shall not be dependent upon
				control power and may consist of a current transformer and overcurrent relay in
				the grounding resistor circuit.
3.7. The trailing cable for the continuous
				miner shall be provided with instantaneous short-circuit protection set at no
				more than the setting specified in the continuous miner approval documentation
				or 75 percent of the minimum phase-to-phase short-circuit current available at
				the continuous miner, whichever is less.
3.8. The short-circuit protective device
				shall contain no intentional time delay and shall be based on the maximum
				asymmetrical starting current or have a time delay of no more than 0.05 seconds
				and be based on the maximum symmetrical starting current. The time delay
				settings shall not exceed the settings specified in the approval
				documentation.
3.9. Guarding made
				of grounded metal or nonconductive flame-resistant material shall be provided
				to minimize the possibility of miners contacting the high-voltage trailing
				cable and to protect the high-voltage trailing cable from damage. The
				high-voltage trailing cable shall be installed on well insulated insulators or
				guarded at the following locations:
3.9.a.
				The high-voltage trailing cable shall be guarded at the power center cable
				coupler for a distance of 10 feet.
3.9.b. The high-voltage trailing cable shall
				be installed on well insulated insulators from the power center to the last
				open crosscut and shall be guarded at any location on the working section where
				it may be damaged by moving equipment. That portion of the trailing cable that
				is located in or inby the last open crosscut shall be hung when other equipment
				cables must cross the high-voltage trailing cable.
3.9.c. The high-voltage trailing cable shall
				be provided with a guard that extends from the high-voltage miner cable
				entrance gland for a distance of a minimum of 10 feet.