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Measuring insulation resistance of cables

Information Source:Henan Huadong Cable Co., Ltd  Release date:2014-02-25

In the testing of cable insulation, often use megohmmeter, but some people may not know about the mechanism, often take the wrong line or the use of incorrect error is large, sometimes even will cause the accident or equipment, we carried on a simple introduction to the matters and methods note ohmmeter to measure cable, may share with you.

Megger while at work, its produce high voltage, and measurement of objects and electrical equipment, so must be properly used, otherwise it will cause the accident accident or equipment. Before use, must do the following preparations.

Must be cut off the power before the measurement test equipment is 1, and the short circuit, must not be allowed to live measurement.
On 2 may induce high voltage electrical equipment, must eliminate this possibility, could be measured.
3 the measured surface should be clean, reduce the contact resistance, ensure the validity of measurement results.
To check the megger is in normal working state of the 4 measurements before, mainly to check the "0" and "control" two. The handle is rotated, the motor rated speed, megger short-circuit should be refers to "0" position, should begin to "∞" position.

M ohm meter when in use should be placed on a stable, firmly in place, and far away from the external electric conductor and the outer magnetic field of.
In measurement, but also pay attention to the correct wiring of megohmmeter, otherwise it will cause unnecessary errors and even mistakes.

Mega ohm meter wiring column in a total of three: one for the "L" line end, a "E" as the end, another "G" shield end (also called protection rings). Generally measured insulation resistance are connected to "L", "E", but when the measured surface of insulator leakage serious, shielding ring must be measured or not measured part is connected with "G". This leakage current is negative side by side "G" directly into the shield generator to form a loop, and no longer measuring mechanism through the mega ohm meter. This fundamentally eliminate the effect of surface leakage current, special attention should be paid to the insulation resistance between the measurement of cable core and appearance, must receive the shield end "G", because when the air humidity is big or the cable insulation surface is not clean, the surface leakage current is very large, in order to prevent the measured because of its internal insulation leakage effects caused by measurements, a metal screen loop in the cable is connected with the megohmmeter, "G" end.

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