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Common problems of loop resistance tester

time:2020/9/30   source:华天电力  reading:253 time

Common problems in the field test of loop resistance tester:


1. The voltage wiring circuit is open or poorly connected (the contact resistance is unlimited when the wiring is disconnected). When there is strong electromagnetic interference around the test. For example, the bus is charged. At this time, the live bus uses air as a medium, which will interfere with the capacitance of the tester. Due to the interference, the differential mode voltage of the two voltage test lines appears at both ends of the voltage acquisition line of the loop tester.


Micro Ohmmeter.png


If the external interference is large, the loop resistance tester will display a value much larger than the resistance value of the product under test. At this time, if the tester has sufficient field test experience, the test result can be judged to be abnormal and the problem can be solved , Can attract attention and finally get the correct test results. However, if the tester is not experienced enough, the resistance value of the switching circuit may be misjudged. And may use power failure to deal with defects, which will cause unnecessary losses to future power generation. If the interference intensity is not too great, the value displayed by the instrument is only within the qualified resistance range of the circuit breaker. This situation is the same as the result of "poor contact of the voltage circuit" and may also lead to misjudgment.


2. The voltage wiring circuit is disconnected, the loop resistance tester is turned on, and there is no strong electric field interference at the test site. In this case, there is basically no differential mode voltage input by the amplifier. Therefore, the test parameter displayed by the instrument is close to zero. If the tester has sufficient field test experience, it can be determined that the voltage loop test line of the instrument is abnormal. After eliminating the abnormality of the instrument voltage loop test line, the final correct test result can be obtained. Otherwise, you may mistake the tester for a problem and interrupt the test. Replacement or refurbishment of the instrument will delay the power-off time and bring unnecessary trouble to the test work.


3. Poor connection of voltage circuit wiring. In most cases, after long-term operation. The terminals of the circuit breaker will produce an oxide film or oil film on the outer surface of the terminal block, and poor contact may occur. In addition, the voltage test clamp itself must produce a certain contact resistance, which will seriously affect the test results.


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