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Analysis for DC Resistance Tester principle

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For many electrical equipment, during the use should make insulation resistance test regularly , for example, during annual plum raining and thunderstorms season, various of electrical equipments form different enterprises, especially for high-voltage equipment, it will suffer different levels of moisture and partial damage, and reduce the insulation resistance, it will direct threaten the personal safety and safe operation of electrical equipment. To avoid accidents, the electrical equipment must be regularly conducted various preventive tests. Also the safety requirements stipulated regulate that: for household appliance, the basic insulation is 2MQ; reinforced insulation is 7MQ, which used to ensure the normal operation and  staff’s safety and electrical equipment.Insulation resistance is the resistance which between the insulating material separating two conductors, and the insulation resistance tester is used to measure the insulation resistance value. To guarantee the safety of electrical equipment operation, for insulation resistance which between the different polarity (different phase) conductors, or between the conductor and casing, it make a minimum requirement. The DC high voltage generator as electrical appliances manufacturer, the production of electrical equipment should make insulation resistance tests under certain voltage before delivery, to ensure proper operation and personal safety.

So it’s important to understand insulating features of the instrument. The factors which influence the Insulation resistance measurements values as follows: temperature, humidity, measured voltage, acting time, residual charge in the windings and surface conditions of insulating. By measuring the insulation resistance of electrical equipment, that can get these purposes:

(1) To understand the insulation structure. The reasonable insulation structure is made of high quality insulating material (or insulation system), it should have good insulation properties and high insulation resistance;

(2) To understand the electrical insulation products processing quality. For poorly insulated electrical products, the insulation performance will be decreased;

(3) To understand the moistening insulation and contaminated situation, when the insulation of electrical equipment from moisture and contamination, the insulation resistance will always decrease;

(4) To check if the insulation is able to withstand the voltage test. When make withstand voltage test, the insulation resistance value of electrical equipment is under a certain limit, it will generate a large test current, causing thermal damage to insulation breakdown and electrical equipment. Thus, for wide range standard tests, it necessary to measure the insulation resistance before test the withstand voltage.

This shows, the insulation resistance magnitude can reflect insulation, and can effective find out defects in general damp, local damp, sever damp penetrating defects. Therefore, to measure the insulation resistance is one of the important way to understand the equipment insulation, and also an indispensable part in insulation preventive test.