Measurement of cable insulation resistance of Zhengzhou first cable Co., Ltd. of Zhengzhou Cable Co., Ltd

  　　  Measurement of cable insulation resistance of Zhengzhou first cable Co
, Ltd
Megohmmeter is often used in the insulation test of cable, but some people may not understand its mechanism
It is often connected to the wrong line or used incorrectly, resulting in great error, and sometimes even personal or equipment accidents
Now we briefly introduce the matters needing attention and methods when megohmmeter measures cable, and would like to encourage you When the megger is working, it generates high voltage, and the measuring object is electrical equipment, so it must be used correctly, otherwise it will cause personal accident or equipment accident
Make the following preparations before use 　　1
Before measurement, the power supply of the tested equipment must be cut off and discharged in a short circuit to the ground
The equipment must not be charged for measurement 　　2
For the equipment that may induce high voltage, the possibility must be eliminated before measurement 　　3
The surface of the measured object shall be clean to reduce the contact resistance and ensure the correctness of the measurement results 　　4
Before measurement, check whether the megger is in normal working condition, mainly check its & ldquo; 0” And & ldquo& infin;& rdquo; Two o'clock
That is, shake the handle to make the motor reach the rated speed
In case of short circuit, the megger should point to & ldquo; 0” Position, which should be at & ldquo& infin;& rdquo; Location 　　5
The megger shall be placed in a stable and firm place and away from large external current conductor and external magnetic field When measuring, pay attention to the correct wiring of the megger, otherwise it will cause unnecessary errors or even errors There are three terminals of the megger: one is & ldquo; L” That is, the line end, one of which is & ldquo; E” That is, the ground end, and another & ldquo; G” Namely * end (also known as protective ring)
Generally, the measured insulation resistance is connected to & ldquo; L”、& ldquo; E” However, when the leakage on the surface of the tested insulator is serious, the * ring or the part that does not need to be measured must be connected with & ldquo; G” The ends are connected
In this way, the leakage current passes through the * terminal & ldquo; G” It flows directly back to the negative end of the generator to form a loop without flowing through the measuring mechanism of the megger
In this way, the influence of surface leakage current is fundamentally eliminated
In particular, it should be noted that when measuring the insulation resistance between the cable core and the surface, it must be connected to the * end & ldquo; G”， Because when the air humidity is high or the cable insulation surface is not clean, the leakage current on the surface is very large
In order to prevent the influence of the measured object on its internal insulation measurement due to leakage, a metal * ring is generally added on the outside of the cable, which is similar to the & ldquo; G” End to end