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The preventive test of high voltage test transformer refers to the regular inspection or test of equipment already in operation according to specified test conditions (such as specified test equipment, environmental conditions, test methods, and test voltage), test items, and test cycles, in order to discover hidden dangers in operating power equipment and prevent accidents or damage to power equipment. It is an important measure to determine whether power equipment can continue to operate and ensure safe operation.
The preventive test of high voltage test transformer can be carried out through the following aspects:
1. Measure insulation resistance
A common and simple test method, usually measured with a megohmmeter. Based on the insulation resistance value of the test object measured at 1 minute, it can detect whether the insulation has concentrated defects, overall moisture, or penetrating moisture.
2. Measure leakage current
Its principle is basically the same as measuring insulation resistance, and the nature of detected defects is roughly the same. However, the power supply used in leakage current measurement is generally provided by high-voltage rectifier equipment, and the leakage current is directly read with a microammeter. It has the characteristics of adjustable test voltage, high sensitivity, good measurement repeatability, convertible insulation resistance value, and the ability to judge insulation defects by measuring absorption ratio.
3. Measure dielectric loss angle
As a highly sensitive test item, it can detect overall moisture, deterioration, degradation, and local defects (through or not through) in small test objects of electrical equipment insulation. However, when the test object is large and the defect volume is relatively small, this method is difficult to detect. It is widely used in electrical manufacturing and in handover and preventive tests of electrical equipment.
4. AC withstand voltage test
One of the destructive tests, it can further diagnose insulation defects of electrical equipment. The AC withstand voltage test is a strict, effective, and direct test method for identifying the insulation strength of electrical equipment. It can detect weaknesses in insulation during normal operation and plays a decisive role in determining whether electrical equipment can continue to operate.
5. DC withstand voltage test
In addition to detecting equipment insulation moisture and deterioration, it has a special role in detecting certain local defects in insulation. The DC withstand voltage test can detect defects that some AC withstand voltage tests cannot. These two tests cannot replace each other and must be applied simultaneously in preventive tests, especially for motors, cables, etc., which should undergo DC withstand voltage tests.
6. Non-destructive test and destructive test
① Non-destructive test: It is conducted at a lower voltage (lower than or close to the rated voltage). Among them, measuring insulation resistance, leakage current, and dielectric loss angle are non-destructive tests.
② Destructive test: It refers to tests conducted at voltages higher than the working voltage, also known as withstand voltage tests. During the test, a specified test voltage is applied to the insulation of electrical equipment to test its withstand capability under this voltage. Both DC withstand voltage test and AC withstand voltage test are destructive tests.
These two types of tests have a certain order: non-destructive tests should be performed first, followed by destructive tests, to avoid unnecessary breakdown accidents.
Note: The above information and technical parameters are compiled and released by Yangzhou Darui Electric Co., Ltd.
