Omicron CP TD1 - Page 95

95
Capacitance and DF Measurement on High-Voltage Bushings
Table 7-1 Bushing faults, part 1 [4.3]
Failure Possible results Methods of detection
Cracked porcelain Moisture enters;
Oil and/or gas leaks;
Filler leaks out
Visual inspection;
Power factor test;
Hot-collar test
Deterioration of
cemented joints
Moisture enters;
Oil and/or gas leaks;
Filler leaks out
Visual inspection;
Power factor test;
Hot-collar test
Gasket leaks Moisture enters;
Oil and/or gas leaks;
Filler leaks out
Visual inspection;
Power factor test;
Hot-collar test;
Hot-wire test for
moisture;
Insulation resistance
Moisture in insulation Moisture enters Power factor test;
Hot-collar test
Solder seal leak Moisture enters;
Filler leaks out
Visual inspection;
Power factor test;
Hot-collar test;
Hot-wire test for
moisture;
Leak detector
Broken connection
between ground sleeve
and flange
Sparking in apparatus
tank or within bushing;
Discolored oil
Power factor test;
Uncharacteristic odor;
Dissolved gas-in-oil
analysis (DGA);
Thermographic scanning
Voids in compound Internal corona Visual inspection;
Power factor test;
Hot-collar test
Displaced grading shield Internal sparking
discolors oil
Hot-collar test;
Uncharacteristic odor;
Thermographic
scanning;
Dissolved gas-in-oil
analysis (DGA)
Electrical flashover Cracked or broken
porcelain;
Complete failure
Visual inspection;
Hot-collar test