Testing method for insulation performance of transformer bushing

Testing method for insulation performance of transformer bushing

Insulation resistance measurement

-Testing method: Connect the measuring lead of the megohmmeter to the corresponding terminal of the bushing. When measuring the main insulation of the bushing, connect one end of the megohmmeter to the bushing conductor and the other end to the bushing shell or grounding terminal; When measuring the insulation of the final screen, connect one end to the final screen and the other end to ground. Apply the specified voltage and read the stable insulation resistance value. Generally, the insulation resistance of the final screen should not be less than 1000M Ω.

Measurement of dielectric loss tangent (tan δ) and capacitance

-Testing method: The positive wire method is used for ungrounded bushings. Connect the high-voltage output of the tester to the bushing conductive rod and the measuring wire to the end screen; The reverse wiring method is used for grounding the bushing, connecting the high-voltage output to the terminal screen, and grounding the measuring wire. Pre set test voltage, start measurement, record dielectric loss value and capacitance.

Frequency domain dielectric spectroscopy (FDS) testing

-Testing method: By measuring the capacitance and dielectric loss values of the transformer bushing at frequencies of 0.1mHz-10kHz, analyzing the measurement results using a model, and judging the insulation state based on the dielectric mass spectrum curve.

AC withstand voltage test

-Testing method: Connect the sleeve to the test circuit, gradually increase the voltage to the specified test voltage value, maintain it for a certain period of time, and observe whether there are any abnormal phenomena such as discharge and flashover in the sleeve.

partial discharge test

-Testing method: Pulse current method, ultrasonic testing method, etc. can be used to apply voltage on the casing and detect the presence and magnitude of partial discharge signals.