METHOD AND APPARATUS FOR MONITORING CAPACITOR BUSHINGS FOR A THREE-PHASE AC SYSTEM

A method for monitoring capacitor bushings (2a, 2b, 2c) for a three-phase AC system, wherein each capacitor bushing (2a, 2b, 2c) has a conductor (4), which is connected to one of the system lines (5a, 5b, 5c) of the AC system, and an electrically conductive lining (3) that surrounds the conductor (4), comprises the steps that-an upper capacitance (C0a, C0b, C0c) and a lower capacitance (C1a, C1b, C1c) are ascertained for each capacitor bushing (2a, 2b, 2c); -a measured voltage (U1a, U1b, U1c) is detected at each capacitor bushing (2a, 2b, 2c), which measured voltage is present between the respective lining (3) and an earth potential (13); -an actual capacitance (C0a′, C0b′, C0c′) is computed for each capacitor bushing (2a, 2b, 2c), which actual capacitance is dependent on the respective measured voltage (U1a, U1b, U1c), the respective lower capacitance (C1a, C1b, C1c) and on the measured voltage (U1b, U1c, U1a), the lower capacitance (C1b, C1c, C1a) and the upper capacitance (C0b, C0c, C0a) of one of the other capacitor bushings (2a, 2b, 2c); the respective upper capacitance (C0a, C0b, C0c) is compared with the respective actual capacitance (C0a′, C0b′, C0c′) for each capacitor bushing (2a, 2b, 2c); a monitoring signal is produced that is dependent on the results of the capacitance comparisons.