Insulation resistance meter use and wiring precautions

Insulation resistance meter is a simple and commonly used direct reading instrument for measuring high resistance. It can be used to measure the insulation resistance of circuits, motor windings, cables, electrical equipment, etc. There are three terminals on the insulation resistance meter marked with grounding (E), circuit (L) and protection ring (G). When using, not only the wiring is correct, the end button is tightened, and the following items should be noted:

(1) Perform an open circuit test and a short circuit test on the insulation resistance meter before measuring to check whether the insulation resistance meter is normal. The specific operation is as follows: open the two connecting lines, shake the handle pointer to point at infinity, and then short the two connecting lines, the pointer should be at zero.

(2) The device under test must be disconnected from other power sources. After the measurement is completed, the device under test must be fully discharged (2 to 3 minutes) to protect the device and personal safety.

(3) The insulation resistance meter and the device under test shall be separately connected by a single strand, and the surface of the line shall be kept clean and dry to avoid errors caused by poor insulation between the wires.

(4) When the measurement is shaken, it will be placed in the horizontal position, and the handle will not be short-circuited when the handle is rotated. When measuring capacitors and cables, the wiring must be disassembled when the handle is rotated. Otherwise, the reverse charging will damage the insulation resistance meter.

(5) When shaking the handle, it should be slow and fast, evenly accelerate to 120r/min, and take care to prevent electric shock. During the shaking process, when the pointer has zero, it can no longer continue to shake, in case the coil inside the watch is damaged by heat.

(6) For larger capacity equipment, such as transformers, motors, cables, etc., it is sometimes necessary to measure the absorption ratio, that is, to measure the ratio of the two resistances of 60s and 15s. When R60/R15>1.3, it can be considered that the insulation is qualified, otherwise the insulation is damp and needs to be dried.

(7) In order to prevent the surface leakage resistance of the device under test, when using the insulation resistance meter, the intermediate layer of the device under test (such as the inner layer insulation between the cable cores) should be connected to the protection ring.

(8) A suitable insulation resistance tester should be selected depending on the voltage level of the equipment under test. For equipment with rated voltage below 500V, use 500V or 1000V insulation resistance meter; for equipment with rated voltage of 500V or above, use insulation resistance meter of 1000~2500V. The selection of the range should generally be careful not to make the measurement range excessively exceed the insulation resistance value of the device under test, so as not to cause a large error in the reading.

(9) It is forbidden to use the insulation resistance meter to measure in lightning weather or in equipment adjacent to the high-voltage conductor.