What are the most common testing methods for high voltage bushings?

Common testing methods include insulation resistance testing, capacitance measurement, power factor (tan delta) testing, and partial discharge (PD) testing. Capacitance and power factor tests help assess the insulation condition, while PD testing detects electrical discharges within the bushing that could indicate insulation breakdown. Dissolved gas analysis (DGA) of the bushing oil is also performed to detect faults.