Out of Megohmmeter Misuse

Megohmmeter is a kind of measuring instrument that is mainly used to detect electric lines and insulation resistance of electrical equipment and home appliances. It is easy to cause certain misunderstandings during the use of Megger. These errors have great influence on the use of Megohmmeters. Today Xiao Bian came to give you a detailed introduction about the misuse of Megger.

Misunderstanding 1:

The megohmmeter's rated voltage is not compatible with the voltage of the electrical equipment under test. That is, different megohmmeters should be used to test transformer high voltage and low voltage coils; AC 2kV is applied to the insulation of the 0.4kV side coil as the withstand voltage test voltage, no breakdown, flashover, etc. within 60s, and 10kV is applied AC 42kV as withstand voltage test voltage. Therefore, the measurable value of the high voltage to the low voltage, high voltage to the ground and the core to the insulation resistance should be 2500V, the range is 2500MΩ or more Megohmmeter. The 0.4kV side of the low voltage can only use 500V or 1000V megohmmeter. If 500V and 1000V megohmmeters are used to measure the high voltage side where the rated voltage is higher than 500V and 1000V, there are errors in the measurement results. If the insulation resistance value of the low-voltage side is measured with a megohmmeter with a high rated voltage, the insulation may be damaged.

Misunderstanding 2:

Did not take two people with the measurement method of operation. "After reading the above values, the test piece should be disconnected without stopping the rotation of the handle, and then the shake can be stopped to prevent the megohmmeter from being damaged due to the charge feedback discharge of the test piece." This is generally used. Instructions for use are common in manuals or textbooks. However, a considerable number of testers shake the cable after the connection. Therefore, many megohmmeter components are damaged, or the megohmmeter is scrapped and repaired after one or two uses. When we use a megohmmeter, we use a two-person operation method to measure. After the test line is connected, one person is responsible for rotating the megohmmeter handle and reading, and the other person is holding the test end to align the sample to listen to the operator of the megohmmeter handle. Command; "pass the sample, pull, discharge" password. Thanks to the use of the Megohmmeter method in conjunction with the operation, the high-level test of our bureau used the ZC series of megohmmeters from 1992 to 2000 to remain intact.

Misunderstanding three:

The use of general flower lines and plastic-bonded wires instead of dedicated megohmmeter lines is an extremely non-standard practice. Because the general flower line, plastic wire insulation value is much lower than the dedicated test line. The special test line will not affect the insulation value due to laps of the test sample by hand. On the contrary, the general flower line and the rubber-bonded wire may also injure the operator during the shaking test. At the same time, it is necessary to properly maintain dedicated test lines, including dedicated power cords and test probes for the ZC48-type electronic megohmmeter.