DIFFERENTIAL-VOLTAGE OPERATING METHOD FOR AC VOLTAGE

PURPOSE:To decrease the operating errors of differential voltages caused by the error of a measuring when the difference in amplitudes and the difference in phases of the AC voltage across a breaker are operated in an automatic synchronous closing device, an automatic resetting device, a network relay or the like. CONSTITUTION:The difference in amplitudes and the difference in phases of two AC voltage across a breaker 1, which are measured with voltage measuring means 101 and 102 under the state wherein the breaker 1 is closed, are operated in differential- voltage-error-compensation-value operating means 103 and 104 beforehand. The results are made to be compensating values. When the difference in amplitudes and the difference in phases of the AC voltages across both ends of the breaker 1 are operated with a differential-voltage operating means 105, the compensating values are substracted, thereby making compensation. The methods for commanding the operation of the compensating values such as a method for issuing the operation command at the operation starting time of an apparatus, the method for issuing the operating command based on the external operation, the method for issuing the operating command by detecting the closding operation of the breaker and th method for issuing the operating command for every specified period are mary appropriately. Thus, the adequate compensating-value operating command is executed.