What is the reason for the large contact resistance during testing?

There are two main reasons why Contact Resistance Tester tests high contact resistance of high voltage switches:

First, the reason for the loop resistance tester

1. The accuracy of the tester itself, it is important to ensure that the accuracy of using the resistance tester is completely correct.

2. Check the terminal blocks on the resistance tester panel to see if there is any contact loosening or oxidation.

3. Make sure that the resistance tester is wired correctly, and check whether the voltage input line is connected to the inside of the current output line.

4. The current clamp of the resistance tester ensures reliable contact with the product under test to avoid excessive contact resistance and affect the test results.

5. Ensure sufficient test time and carry out the test according to the time specified in the national standard.

Second, the contact resistance of the high-voltage switch itself is too large.

1. Whether the ends of the high-voltage switch are grounded. If both ends are grounded, a parallel circuit is formed. The test results are the loop resistance of the circuit breaker and the ground resistance of the substation. The correct thing to do is that at least one end of the high voltage switch is not grounded.

2. The surface of the dynamic and static contact of the high-voltage switch is oxidized.

3. Mechanical impurities or carbides remain between the dynamic and static contacts of the high-voltage switch.

4. The pressure and high pressure switch are moving, and the static contact is reduced (such as mechanical jamming, contact snapping, annealing, etc., resulting in a drop in contact pressure).

5. The contact area of the dynamic and static contacts of the loop resistance tester is reduced, and the static contact of the high-voltage switch is reduced (improper adjustment or displacement of the contact surface during operation, and the load current and short-circuit current are interrupted for many times, resulting in a decrease in the effective contact area).