| 摘要 |
A system and a method to determine the impedance of an electrical facility being disconnected from its high or medium voltage power supply. A signal injectionunit injects a test signal at a main frequency between a reference point of an electric circuit and ground, where the electric circuit is connected with the facility and injects another test signal at a second main frequency between a reference point of the electric circuit and ground. A signal conversion unit measures a first response voltage and a first response current in the electric circuit, where the first response voltage and the first response current result from the test signal and measures a second response voltage and a second response current as a result to the other test signal. A processing device determines an impedance to ground of the facility from the first response voltage and the first response current and determines another impedance to ground from the second response voltage and second response current, analyses impedances to ground of the facility, where this analysing includes comparing each determined impedance to ground with a predetermined value, and determines a safety state of the disconnected electrical facility based on the analysed impedances to ground. |
