What should be noted when using insulation resistance tester

Measurement of insulation resistance, generally used insulation resistance tester for testing. Insulation resistance tester is also called digital megohmmeter, pointer megohmmeter, insulation meter, insulation resistance tester, high-voltage insulation resistance tester, insulation resistance measuring instrument, insulation characteristics tester, high-voltage megohmmeter, megohmmeter with absorption ratio function, megohmmeter with polarization index function, electric shaking table, electronic insulation resistance tester, high-power high-voltage megohmmeter and so on.

(A) insulation resistance tester principle:

Insulation resistance tester is mainly through a voltage excitation of the device or network under test, and then measure the current generated by the excitation, using Ohm's law to measure the resistance. These electrical testers apply a much higher voltage when making resistance measurements compared to the ohmmeter function equipped on a digital multi-meter (DMM), for example. Megohmmeters employ voltages that typically range from 50 V to as high as 5 kV; whereas typical digital multimeters typically have voltages of less than 10 V. For insulation testing, where a wide range of resistance values need to be measured, with an upper limit of up to 10 TΩ, higher voltages are required.

(2) Insulation Resistance Tester Performance:

Insulation resistance testers, often referred to as megohmmeters or high-resistance meters, are widely used to measure the insulation resistance of generators, motors, power transformers, wiring, appliances, and other electrical devices (such as cables for control, signaling, communications, and power). They are often used in routine maintenance programs to indicate changes in insulation resistance of motors over months or years. A large change in insulation resistance can indicate a potential failure. So it becomes necessary to calibrate the megohmmeter periodically to ensure that the meter itself has not changed over time.

(C) insulation detector use:

Insulation detector in the work, itself generates high voltage, and the measurement object is electrical equipment, so it must be used correctly, otherwise it will cause personal or equipment accidents. In the use of megohmmeter before, first of all, we must do the following various preparations:

(1) before the measurement must be measured before the equipment power cut off, and short-circuit discharged to ground, never allow the equipment charged for measurement to ensure the safety of persons and equipment

(2) on the equipment that may induce a high voltage, it must be eliminated after the possibility of such measurements can only be carried out.

(3) The surface of the measured object should be clean to reduce the contact resistance and ensure the correctness of the measurement results.

(4) Measurement should be checked before the megohmmeter is in normal working condition, mainly to check its "0" and "∞" two-point position. That is, shake the hand generator handle, so that the motor to reach the rated speed. Megohmmeter in the short-circuit, the pointer should point to the "0" position; open circuit, the pointer should point to the "∞" position.

(5) Insulation tester should be placed in a stable, solid place, and away from large external current conductor and external magnetic field.

(6) must be correctly wired. Megohmmeter generally have three terminals, which L connected to the measured object and the earth insulated conductor part, E connected to the measured object shell or the earth. g connected to the shield of the measured object or do not need to measure the part. Measurement of insulation resistance, generally only "L" and "E" end. But in the measurement of the insulation resistance of the cable to ground or the measured equipment leakage current is more serious, it is necessary to use the "G" end, and the "G" end of the shield or shell. After the line is connected, you can turn the crank in a clockwise direction. Shake the speed should be slow and fast, when the speed reaches about 120 revolutions per minute (ZC-25 type), to maintain a uniform speed of rotation, 1 minute after the reading. And to read while shaking. Can not stop reading.

(7) shaking test will be placed in the horizontal position of the megohmmeter, shaking the knob between the end of the rotation is not allowed to short circuit. Shake the handle should be slow and fast, if you find that the pointer points to zero that the insulator may be short-circuited, then you can not continue to shake the handle. In order to prevent the table coil heat damage.

Reading completed. The measured equipment will be discharged. Discharge method is to measure the use of the ground wire from the megohmmeter down and the equipment under test can be shorted (not insulation tester discharge).

(D) insulation tester notes:

(1) prohibited in the lightning or high-voltage equipment near the measurement of insulation resistance, only in the equipment is not charged. There is no induced electricity in the case of measurement.

(2) shaking measurement process. The measured equipment can not be someone working.

(3) insulation detector line can not be twisted together. To separate.

(4) megohmmeter did not stop turning before or before the equipment under test is not discharged. It is strictly prohibited to touch with hands. Remove the wire, do not touch the metal part of the lead.

(5) At the end of the measurement. For large capacitance equipment to be discharged.

(6) megohmmeter terminal leading to the measurement of flexible wire insulation should be good, between the two wires and between the wire and ground should be maintained at an appropriate distance, so as not to affect the measurement accuracy.

(7) in order to prevent the measured equipment surface leakage resistance, the use of megohmmeter. The intermediate layer of the equipment under test (such as the inner insulation between the cable shell core) should be connected to the protective ring.

(8) To periodically calibrate its accuracy.