Circuit breaker AC withstand voltage test characteristics and precautions - Database & Sql Blog Articles

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The AC withstand voltage test is the most direct and effective method to finally check the insulation state of the oil circuit breaker. During the test, the general methods, procedures and precautions of the AC withstand voltage test shall be observed, and the following items shall be noted for the characteristics of the circuit breaker.

1. Test procedure: The AC withstand voltage test shall be carried out after the tests of insulation resistance, leakage current, dielectric loss tangent and insulating oil are passed. For filter oils or newly refueled circuit breakers, the test should be carried out with the oil fully static. The rest time is generally not less than 3 h to avoid unnecessary discharge or breakdown due to the presence of air bubbles.

2. The multi-oil circuit breaker should be tested in the closed state. Multi-oil circuit breakers with three phases in the same fuel tank shall be tested in phase separation; when one phase is tested, the other two phases and the fuel tank are grounded together.

3. The oil-less circuit breakers should be tested under closing and opening respectively. The purpose of the test in the closed state is to test the electric strength of the strut insulator, and the test purpose in the open state is to test the electric strength of the bushing insulator between the fuel tank and the conductive rod. When testing under the opening, a voltage should be applied between the in-phase moving contact and the stationary contact.

4. Since the circuit breaker has small capacitance and the test capacity rise phenomenon is not obvious, there is no special requirement for the test voltage, and the test voltage can be directly measured from the low voltage side of the test transformer.

5. Analysis and judgment of the test results: There is no significant change in the insulation resistance before and after the test, and the general drop is not more than 30%. During the test: If there is intermittent sound of slight discharge in the fuel tank, the fuel tank should be put down for inspection. If necessary, the oil should be re-filtered. If a dull breakdown or smoke is found, it is considered unqualified. At this time, it should be overhauled. Handling; if the organic insulating material burns out, it should be replaced and the cause should be identified and cannot be easily retested.