What is the Reason for larger Contact Resistance When Testing?
Contact Resistance Tester test high voltage switch contact resistance with larger resistance value is mainly for two reasons:
First, the reason of the contact resistance tester. 1, The accuracy of the contact resistance tester itself, it is important to ensure that the accuracy of the contact resistance tester is completely correct. 2. Check the terminal on the contact resistance tester if there is contact loosening or oxidation. 3. Make sure that the contact resistance tester is wired correctly, and check whether the voltage input line is connected to the inside of the current output line. 4. Ensures reliable contact of the current clamp of the contact resistance tester with the test object to avoid excessive contact resistance and affect the test result. 5. Ensure sufficient test time and conduct tests according to the time specified by national standards.
Second, the contact resistance of the high-voltage switch itself is too large. 1. Whether the two ends of the high-voltage switch are grounded. If both ends are grounded, a parallel circuit is formed. The test results are the circuit resistance of the circuit breaker and the ground resistance of the substation. The correct approach is to at least not ground one end of the high-voltage switch. 2. Oxidation of the surface of the dynamic and static contacts of the high-voltage switch. 3. Residual mechanical impurities or carbides between the dynamic and static contacts of the high-voltage switch. 4.High voltage switch, static contact drop (such as mechanical jam, contact bullet breakage, annealing, etc., resulting in contact voltage drop). 5. The contact area of the contact resistance tester is reduced by the contact area of the high voltage switch (improper adjustment or displacement of the contact surface during operation, and the load current and the short-circuit current are interrupted many times, resulting in a decrease in the effective contact area).