| 摘要 |
PURPOSE:To detect real earth resistance by subtracting the current of an earth system which is connected to an earth system to be detected from a current flowing through the latter system. CONSTITUTION:Earth networks 121 and 122 of other electric stations are connected to an earth network 7 through aerial earth wires. A current transformer 13 is connected between a constant current amplifier 5 and the earth network 7 to detect a current I flowing through the earth network 7 and current transformers 141 and 142 are connected between the earth network 7 and other earth networks 121 and 122 to detect currents I1 and I2 flowing through the earth networks 121 and 122. An adder 15 is connected to output terminals of the current transformers 13, 141, and 142 and the currents I1 and I2 flowing to other earth systems are subtracted from the current I flowing to the earth system to be measured, thus obtaining a current I0. The current I0 is the earth current of this electric station and the current voltage V is measured by a voltage measuring part 8 to measure only the earth resistance of this electric station with high precision.
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