Ground circuit impedance measurement apparatus and method

A ground circuit impedance measurement device, comprising:

• means for circulating AC current through a ground circuit and means for measuring an AC voltage drop across the ground circuit to determine circuit impedance, further comprising:
• a ground circuit having an electrical AC current source for providing electrical power to the around circuit;
• a main circuit breaker and a visible disconnect switch;
• a high voltage coupler at the end of the circuit;
• an ammeter and voltmeter;
• means for adjusting AC current to 25 amperes or less, thereby simulating a around fault by passing the AC current through the ground circuit;
• means for measuring total AC voltage drop across the ground circuit;
• and
• means for determining around impedance by dividing the AC voltage drop by the AC current reading to determine impedance directly.

A method of measuring ground impedance by dividing an indicated AC voltage by an indicated AC current on cables longer than one mile, comprising:

• a) providing a ground circuit in an underground coal mine having an electrical AC current source for providing electrical power to the ground circuit;
• b) disconnecting power by opening a main circuit breaker and a visible disconnect switch;
• c) inserting a high voltage coupler at the end of the circuit;
• d) connecting the electrical AC current source with an ammeter and voltmeter by alligator clips to two phase wires and to a ground wire;
• e) providing and adjusting electrical AC current to 25 amperes or less, thereby simulating a ground fault by passing the electrical AC current through the ground circuit;
• f) measuring total AC voltage drop across the ground circuit wherein the power wires of the circuit being measured serve as a means of transmitting voltage and current data;
• and
• g) determining ground impedance by dividing the AC voltage drop by the AC current reading to determine impedance directly and displayed automatically.