Abstract: 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.

Abstract: Three-phase power equipment while still connected to the three-phase line has the insulation qualities of its various phases tested. All ground connections of said equipment except one are disconnected and that one is reconnected through ground current sensing means. Coupling units which may be capacitors are respectively connected between each of the three phases of the power line to which the power equipment is connected and ground. Each coupler unit is a reference phase current sensing means. Adjustable phase and magnitude adjustor means are used to couple the respective phase current sensing means to a summing means so that they are adding. The ground current sensing means is similarly coupled to the same summing means but opposed to phase current effects. A null detector coupled to the summing unit detects when balance occurs.