Never

When may work be performed on energized high voltage lines underground?

Deenergized, disconnected, locked out, tagged, and grounded. These precautions must be taken by a qualified person.

What precautions must be taken before work is performed on surface or underground high voltage lines?

Before use (DUH!!!!!!)

When should an electrician inspect his personal protective equipment?

Discarded and replaced prior to the performance of any electrical work.

What should be done with equipment that is found to be defective?

ASTM standards part 28 published in 1968

All rubber protective equipment used on work on energized high-voltage surface lines shall be electrically tested by the operator in accordance with what standards?

Once each month Once every three months Once every six months Once a year

How often shall rubber gloves be tested? Rubber sleeves? Rubber blankets? All other protective equipment?

Wear high voltage gloves and use insulated sticks or pullers

What are two precautions to be taken when operating disconnects or cutout switches on energized high voltage surface lines?

Idle days and shifts The exceptions are rectifiers and transformers

When should underground power circuits be deenergized and what are two exceptions to this rule?

Undervoltage Grounded phase Short circuit Overcurrent

All three phase circuit breakers must be equipped to trip under what four electrical conditions?

Surface

Where must circuit breakers protecting high voltage circuits entering an underground area be located?

40 to 60 percent

Ground check relays may be used for under voltage protection if the relay coils are designed to trip the circuit breaker when line voltage decreases to what percent of the nominal line voltage?

The smallest conductor

One circuit breaker may be used to protect two or more branch circuits if the circuit breaker is adjusted to afford overcurrent protection for what conductor?

Monthly be a qualified person

How often must high voltage circuit breakers protecting underground circuits be tested and examined and by whom?

Visual examinatin Break continuity of the ground check circuit Actuate at least two relays

What are three items that tests and exams for high voltage circuit breakers protecting underground circuits be tested and examined?

In a secure book that is not susceptible to alteration or electronically in a computer system so as to be secure and not susceptible to alteration

What type of record of testing, examinatins and repairs or adjustments of all circuit breakers protecting high voltage circuits which enter any underground area of the mine must be made and maintained by the operator?

1 year and available to authorized representative of the secretary, the representative of miners and other interested persons.

How long must records be retained at a surface location at the mine and to whom shall these records be made available?

100 Maximum fault current continuously and it shall be insulated to phase to phase of voltage of the system

On high voltage systems the grounding resistor where required must limit the voltage drop in the grounding circuit external to the resistor to not more than how many volts under fault conditions? What minimum current rating is required for this grounding resistor and it shall be insulated from ground for a voltage equal to what?

100 feet

Visual disconnects must be installed within how many feet of the point where high voltage circuits enter the underground portion of the mine?

When either the ground or pilot check wire is broken or other no less effective device approved by the Secretary to assure such continuity.

High voltage resistance grounded systems shall include a fail safe ground check circuit to monitor cointinuously the grounding circuit to assure continuity. The ground check circuit shall cause the circuit breaker to open when what condition exists?

96 volts

What is the maximum voltage allowed on high voltage ground check circuits?

There must be metallic shields around each power concutor. The grouding conductor must be one half the size of the power wire and the ground check conductor must be External No. 8 AWG Internal No. 10 AWG

What are the shielding requirements for underground hig voltage cables used in resistance grounded systems? What size grounding conductor is required? What size insulated ground check conductor is required?

All components

Splices made in high voltage cables shall provide continuity of what?

It shall be grounded to the ground conductor in the cable. The ground check should be broken first and the ground conductor shall be broken last.

How shall all exposed metal on medium and high voltage metallic couplers be grounded? It shall be constructed so that which conductor is broken first when the coupler is being disconnected? Which shall be broken last?

Phase to phase

How must single phase loads be connected in three phase resistance grounded systems?

They shall be installed only in REGULARLY INSPECTED air coursers and haulageways, protected against DAMAGE, guarded where men regularly work or pass under them unless they are 6 AND 1/2 FEET or more above the floor or rail, securely anchored, properly insulated guarded at ends and protected from contact with trolley wires and other LOW voltage circuits.

What are the requirements for installation of underground high voltage transmission cables?