Why should the insulation performance of electrical equipment be strictly required?

Electrical test equipment: According to the different test functions and requirements, the test of electrical equipment can be divided into two categories: insulation test and characteristic test. 1, insulation test: insulation defects of electrical equipment, one of which is hidden during manufacturing; One is developed under the influence of the outside world. External effects include working voltage, overvoltage, humidity, mechanical force, thermal effect and chemical effect. The insulation defects caused by the above reasons can be divided into two categories: (1) concentrated defects, such as porcelain cracking of insulators; Local wear and extrusion rupture of generator insulation; The air gap of cable insulation is partially discharged under the action of voltage, which gradually damages the insulation; Other mechanical damage, local humidity, etc. (2) Distributed defects. Refers to the decline of the overall insulation performance of electrical equipment, such as organic substances in insulation such as motors and bushings. The existence of internal insulation defects reduces the insulation level of electrical equipment. We can detect hidden defects through some experimental methods. Testing methods are generally divided into two categories: a. nondestructive testing. It refers to measuring various characteristics at low voltage or by other methods without operating insulation to judge the defects inside insulation. Practice has proved that this method is effective, but some defects can not be fully exposed because of the low test voltage. At present, it is not possible to judge the insulation level reliably by it alone, and it is necessary to continuously improve the nondestructive testing method. B. destructive test or pressure test. This test requires strict insulation, especially the concentrated defects that expose dangerous traps. Through this test, a certain level and margin of insulation can be ensured. Its disadvantage is that it may damage the insulation of the tested equipment to a certain extent, but it is still a main method in insulation testing at present. In order to avoid the harmless damage of destructive test to insulation and increase the difficulty of repair, destructive test is often carried out after nondestructive test. If NDT shows insulation abnormality, it is necessary to carry out NDT after finding out the reason and eliminating it. 2. Characteristic test: Tests other than general insulation tests are collectively called characteristic tests. This kind of test mainly tests some electrical or mechanical characteristics of electrical equipment, such as transformer, transformer ratio test and polarity test; Measurement of DC resistance of coil: resistance of conductive loop of circuit breaker; Opening and closing time and speed test, etc. The purpose of the above tests is the same, that is, to expose defects. , but each has certain limitations. Testers should make a longitudinal comparison based on the test results, combined with the factory and historical data, and make a horizontal comparison with the test data and standards of the same type of equipment, and judge the defects or weak links of the equipment through comprehensive analysis, so as to provide a basis for maintenance and operation.