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Reasons for excessive circuit breaker resistance

time:2020/12/2   source:华天电力  reading:289 time

Test standards for circuit resistance of high-voltage circuit breakers and the reasons for excessive resistance. The resistance of the circuit breaker's conductive circuit mainly depends on the contact resistance between the moving and static contacts of the circuit breaker. The resistance of the conductive circuit of a high-voltage circuit breaker mainly depends on the contact resistance between the moving and static contacts of the circuit breaker. The existence of contact resistance increases the loss of the conductor when it is energized and increases the temperature of the contact. Its value directly affects the current carrying capacity during normal operation, and to a certain extent the short-circuit current cut-off capacity. Therefore, the resistance of each phase of the circuit breaker is an important data for the installation, maintenance, and quality acceptance of the circuit breaker.


The loop resistance value is a parameter that characterizes whether the conductive loop is well connected. Various types of products have specified values within a certain range. If the loop resistance exceeds the specified value, it is likely that a certain connection of the conductive loop has poor contact. The local temperature rise in the poor contact area increases during high current operation. In severe cases, it may even cause a vicious cycle to cause oxidation burns. Special attention should be paid to circuit breakers used for high current operation.


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The contact resistance increases due to oxidation of the contact surface and poor contact fastening. When a large current flows, the temperature of the contact point increases, which accelerates the oxidation of the contact surface and further increases the contact resistance. Continuing will cause serious accidents, so it is necessary to measure the contact resistance frequently or regularly.


If the loop resistance tester is tested, the circuit resistance of the circuit breaker is too large. Please focus on checking the following parts of the circuit breaker, and initially repair the excessive circuit resistance of the circuit breaker.


1. Whether the connecting screws between the static contact base and the support, and the middle contact and the support are tightened. Whether the spring is flattened, check for looseness or discoloration.


2. Whether the contact fingers of the moving contact, the static contact and the middle contact are defective or singeed, and whether the surface coating is intact.


3. Whether the elasticity of each contact finger is even and suitable. Whether the spring behind the contact finger falls off, is annealed or discolored, replace the damaged parts.


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