Five Key Tests for Circuit Breaker Life Extension – Which Tests Must Be Passed to Continue Service?

Insulation performance and main-circuit resistance testing are the primary items. Use a high-voltage meter to measure insulation performance, and simultaneously use a dielectric loss tester to obtain the dielectric dissipation factor. It is required that the increase in the dielectric dissipation factor compared to the factory value shall not exceed 30%, and the absolute value shall not exceed 0.8%, so as to verify that the insulation has not been affected by moisture or aging.

The resistance of the conductive circuit is measured using the DC voltage drop method. If the measured resistance exceeds 1.2 times the factory value, it indicates severe contact wear, which must be treated with caution.

Mechanical operation and secondary-circuit testing are equally critical. Perform opening and closing operations at 30%–65% of the rated voltage to verify the reliability of the mechanism under low-voltage conditions, and measure the mechanical travel speed.

Simultaneously, check the insulation of the secondary circuits to prevent aging of control wiring that could cause maloperation or failure to operate.

The AC withstand voltage test serves as the final assessment: apply 80% of the factory test voltage for one minute to verify the overall insulation margin.

Only after all five tests are passed can the vacuum circuit breaker be approved for continued service, but the extended service period should not exceed 5 years. The decision on life extension is not merely a relaxation of age limits; it must be based on test data.

Only when risks are controlled can continued use be justified – this is the true responsibility towards both the equipment and the power grid.

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