Coil insulation diagnostic method for high-voltage rotating electrical machines

摘要

PROBLEM TO BE SOLVED: To detect the positions of the partial discharges generated clearly and to enable a coil insulation to be applied to a high voltage rotary electric machine by comparing frequencies or the like, at which partial discharges occur in a coil for diagnosis and a coil for actual mounting. SOLUTION: A voltage with a low frequency is applied to a coil for diagnosis before hand and raised gradually to find the maximum dischargeable electric charge value of a partial discharge and a partial discharge start voltage Vi. Once the voltage is turned off, an AC voltage is applied with the voltage value and frequency thereof higher than the partial discharge start voltage Vi, while the maximum dischargeable electric charge value is not given. Then, the frequency is lowered gradually to find a frequency (f) at which a partial discharge giving the maximum dischargeable electric charge value will occur. A correlation of the frequency involving the occurrence of the partial discharge is obtained previously with the applied voltage, the partial discharge start voltage and the known position of the partial discharge generated. The position of the partial discharge to be generated in a coil mounted actually is diagnosed by comparing the frequency involving the occurrence of the partial discharge, the applied voltage and the partial discharge start voltage between the coil for diagnosis and the coil for mounting.