FAULT JUDGING APPARATUS FOR GAS INSULATED ELECTRIC APPARATUS

摘要

PURPOSE:To obtain a fault judging apparatus for gas insulated electric apparatus that is capable of judging the presence or absence of a ground fault or short circuit with accuracy, regardless of the waveform of signals for gas pressure in a gas compartment. CONSTITUTION:A gas insulated electric apparatus is composed of a plurality of gas compartments in succession as follows: A power application conductor is placed in a cylindrical metal case, and an insulating spacer is placed at both ends of each compartment-to-be to partition the case and to insulate and support the power application conductor. Each gas compartment is filled with insulating gas. A fault judging apparatus for gas insulated electric apparatus judges the presence or absence of a ground fault or short circuit in the power application conductor, by detecting a variation in gas pressure of the gas compartment of such a gas insulated electric apparatus by means of a gas pressure detector installed on the metal case. A waveform shaping circuit shapes the gas dynamic pressure signal corresponding to a variation in gas pressure, detected by the gas pressure detector, into a pulse signal based on an external threshold signal. A pulse cycle measuring circuit detects the cycle signal corresponding to the cycle of the pulse signal. A judging circuit judges the presence of a ground fault or short circuit if the detected cycle signal is equal to 1/2 of the cycle of the commercial frequency.