James G. Biddle Company

Harry L Latham, Jr

Grounding of poles in a power distribution system is checked by disconnection of the ground wire from the buried grounding conductor (rod) and measurement of the reference ground by conventional techniques. If necessary the grounding conductor is enlarged to lower ground resistance to an acceptable level between 5 and 10 ohms. A pulse generator is then connected between the grounding conductor and the ground lead at the reference pole to generate and transmit through the system netural wire a pulse, preferably on the order of 5 kHz to simulate lightning strikes on the systme neutral. Adjacent poles are then checked one at a time using a current type pickup with peak detector equipment. It is necessary to disconnect the ground wire from the ground connector. A first value is obtained by checking the effects of a pulse in the neutral wire of the distribution system adjacent the selected pole and the output is adjusted by a potentiometer to read 100. Then the pickup is moved to the ground wire and a measurement is made as a pulse passes through the system. The output shown on the meter is in terms of the percentage of the current taken at the neutral. That percentage is applied to a lookup table created by a simulated system in order to give the ground resistance at the selected pole. Additional ground conductors may be added if necessary until ground resistance is sufficiently low. The process is repeated from pole to pole. Equipment is provided in the system to give the input pulse and make current detection at each selected pole using a peak detection reading.

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Huntingdon Valley, PA, United States of America

Harry L Latham, Jr