2021

What measures can be taken to prevent oxidation of high-voltage circuit breaker contacts?

High-pressure circuit breakers operate very frequently and are subject to mechanical and electrical factors, often resulting in failure to trip. For circuit breakers already in operation, if a fault recurs on the load side of the circuit breaker, failure to trip will inevitably cause cascading tripping, expanding the scope of accidents and power outages; therefore, it should be eliminated as soon as possible.

Measures to reduce contact resistance and prevent contact oxidation include:
(1) Use materials with low resistivity and compressive strength to manufacture contacts.
(2) Increase the pressure between the contact surfaces using springs or spring washers.
(3) For easily oxidized copper, brass, and bronze contacts, plate the surface with a protective layer of tin, lead-tin alloy, or silver to prevent increased contact resistance due to oxidation.
(4) Apply a layer of neutral Vaseline oil to the surface of aluminum contacts to prevent oxidation.
(5) Use welded copper-aluminum transition joints.
(6) In the structure of breakable contacts, there is a certain degree of relative sliding between the moving and static contacts, which can wipe off the oxide layer during opening and closing (called self-cleaning), thereby reducing contact resistance.

The DHL-100P intelligent loop resistance tester is developed by Dingsheng Electric Power according to the Ministry of Electric Power standard SD301-88 "Rules for the handover and preventive testing of AC 500KV power equipment" and the new version of "Preventive testing rules for power equipment", which stipulates that the DC current for measuring the contact resistance of circuit breakers and isolating switches shall not be less than 100, to ensure the accuracy of the test results. The loop resistance tester adopts the latest switching power supply technology, which can continuously output large current for a long time, overcoming the shortcomings of instantaneous current of pulse power supply, and can effectively break through the oxide film of switch contacts, obtaining good test results.