What are the common defects in electrical equipment insulation?



During manufacturing, operation, maintenance, installation, storage, and transportation, due to various factors, the insulation of electrical equipment often has the following two types of defects:

One type is concentrated defects that are small in scope but highly harmful. For example, local damage caused by mechanical damage during manufacturing and assembly, local extrusion, ceramic cracking, and internal bubbles. The insulation defects of this type are prone to expand under high voltage and strong electric fields, and are often the main cause of equipment insulation accidents.

 

The other type is distributed defects that are wide in scope. For example, overall moisture absorption or contamination of insulation due to poor sealing, or during long-term operation, under the action of strong electric fields and high temperatures, the dielectric ages, causing overall insulation performance to decline, insulation resistance to decrease, loss to increase, heating to be severe, further accelerating aging, and shortening the insulation life of equipment.

 

 

How are insulation test items for electrical equipment classified?

 

Regularly testing the insulation of electrical equipment can timely discover insulation hazards and deal with them, which is an effective measure to avoid major accidents during the operation of electrical equipment and ensure the normal operation of equipment. Insulation test items can be divided into two major categories.

 

One category is non-destructive tests. These tests have lower test voltages, do not harm equipment insulation, and are simple and easy to perform. By measuring relevant insulation parameters, the insulation condition is judged. Commonly performed non-destructive tests include insulation resistance and absorption ratio measurement, DC leakage current measurement, dielectric loss tangent measurement, and voltage distribution measurement of insulator strings.

 

The other category is destructive tests. The test voltage of these tests is much higher than the rated voltage of the tested equipment, causing some damage to equipment insulation during the test, but they can effectively detect some serious defects in equipment insulation. They are appraisal tests. Commonly performed destructive tests include DC withstand voltage and AC withstand voltage tests.