Principle of DC resistance tester

Many electrical equipment also need to be tested for insulation resistance regularly during use. Various electrical equipment in various companies, especially high-voltage equipment, will be damp or partially damaged to varying degrees, which will reduce the insulation resistance of the electrical equipment and directly threaten the safe operation of the electrical equipment and the personal safety of the staff. In order to prevent accidents, various preventive tests must be carried out on electrical equipment regularly.

Factors that affect the insulation resistance measurement value include: temperature, humidity, measurement voltage and action time, residual charge in the winding and surface condition of the insulation. By measuring the insulation resistance of electrical equipment, the following purposes can be achieved:

(1) Understand the insulation performance of the insulation structure. A reasonable insulation structure (or insulation system) composed of high-quality insulation materials should have good insulation performance and high insulation resistance;

(2) Understand the insulation quality of electrical products. If the insulation quality of electrical products is poor, their insulation performance will be significantly reduced;

(3) Understand the moisture and contamination of insulation. When the insulation of electrical equipment is damp or contaminated, its insulation resistance will usually drop significantly;

(4) Check whether the insulation can withstand the withstand voltage test. If a withstand voltage test is performed when the insulation resistance of the electrical equipment is lower than a certain limit, a large test current will be generated, causing thermal breakdown and damaging the insulation of the electrical equipment. Therefore, various test standards usually stipulate that the insulation resistance must be measured before the withstand voltage test.