Voltage withstand test - electrical performance test

Date：2021-11-01 18:26:32Views：3794

Voltage withstand test is one of the main methods to test the overvoltage withstand capacity of electrical appliances, electrical equipment, electrical devices, electrical circuits and electrical safety appliances.

The withstand voltage test is to detect the leakage current flowing through the insulation system of the tested object and apply it to the insulation system at a voltage higher than the working voltage; while the power leakage current (contact current) is to measure the leakage current of the tested object under the most unfavorable conditions (voltage and frequency) under the normal operation of the tested object.In short, the leakage current of voltage withstand test is the leakage current measured without working power supply, and the power supply leakage current (contact current) is the leakage current measured under normal operation.

For electronic products with different structures, the measurement of contact current also has different requirements, but in general, the contact current can be divided into ground leakage current, surface to ground contact current surfadet0lineleakage current and surface to surface leakage current.

Basic principle of withstand voltage test

Apply a voltage higher than the normal working voltage to the insulator of the equipment under test for a specified period of time. If the insulation is good enough, the voltage applied will only produce a small leakage current. If the leakage current of an insulator of the tested equipment remains within the specified range within the specified time, it can be determined that the tested equipment can operate safely under normal operating conditions.

Voltage withstand test method

1. Hydraulic test

1) During the test, an exhaust port shall be set at the top of the container, and the air in the container shall be exhausted during liquid filling. During the test, the outer surface of the container shall be kept dry.

2) When the wall temperature of the pressure vessel is approximately the same as the liquid temperature, it can be pressurized.

3) During the test, the pressure shall rise slowly. After reaching the specified test pressure, the pressure holding time shall generally not be less than 30min, and then reduce the pressure to 80% of the specified test pressure for a long enough time to check all welded joints and connecting parts. In case of leakage, retest after repair.

4) The pressure shall remain unchanged during the inspection, and continuous pressurization shall not be used to maintain the pressure. During the hydraulic test, do not tighten the bolts under pressure or apply external force to the pressure components.

5) For spherical storage tanks, the hydraulic test method shall meet the requirements of 8.10.4.4 in GB 12337-1998.

2. Pneumatic test

1) Safety measures shall be taken for pneumatic test, which shall be approved by the general technical director of the test unit. During the pneumatic test, the safety department of the test unit shall supervise the implementation of safety measures on site.

2) During the test, the pressure shall rise slowly. When it reaches 10% of the specified test pressure and does not exceed 0.05Mpa, maintain the pressure for 5min, and conduct the initial leakage inspection for all welded joints and connecting parts with soap solution or other leakage detection solution. If there is any leakage, repair and retest. After passing the initial leakage inspection, slowly increase to 50% of the specified test pressure. If there is no abnormality, then increase the pressure step by step according to 10% of the specified test pressure until the specified test pressure. After maintaining the pressure for 30min, reduce the pressure to 87% of the specified test pressure and maintain it for a long enough time, and check the leakage of all welded joints and connecting parts again. In case of leakage, retest according to the above provisions after repair.

3) The pressure shall remain unchanged during the inspection, and continuous pressurization shall not be used to maintain the test pressure. During the pneumatic test, it is strictly prohibited to fasten bolts under pressure and apply external force to pressure components.

4) For spherical storage tanks, the pneumatic test method shall also meet the requirements of 8.10.5.5 in GB 12337-1998.

Purpose of voltage withstand test

All products have a default voltage / current tolerance at the beginning of design. The withstand voltage test is to evaluate the insulation capacity of the product by giving the product a high voltage far beyond the normal condition and measuring the leakage current. When the leakage current exceeds a certain value, it will cause harm to the operator and even endanger life safety. Therefore, withstand voltage test is a common but important electronic safety test.

The withstand voltage test is to apply a high test voltage to the test object, and then maintain it for a period of time and then reduce it to zero. The voltage application time of different products is different, ranging from 2s to 5min, which is determined according to the different requirements of different test objects. Some matters need to be paid attention to in the withstand voltage test. Grounding measures need to be taken in the withstand voltage test, During the test, you must stand on the insulating pad or sit on the stool padded with insulating materials. You can't touch the metal part of the instrument with your hands, because the test voltage of the instrument is tens of kilovolts, which will cause personal safety. The withstand voltage tester can't test in the overtime environment, because the humid air will become a conductor, Breakdown will occur during the test, resulting in inaccurate test results.

The voltage withstand test includes long-term test and field test. The long-term test is the kind of test with high requirements. The delivery test is widely used. Generally, the test time is less than 5S, and it is qualified if the detected overvoltage meets the requirements of the specified value. The delivery test of the voltage withstand test is widely used in industries such as insulation materials, switchgear plants, wire and cable material plants, etc, Become one of the essential tests.

Measurement standard of voltage withstand test

During the withstand voltage test, the measurement standards are different for the tested objects with different technical specifications. For the general tested equipment, the withstand voltage test is to measure the leakage current value between the live wire and the shell. The basic requirement is: double the working voltage of the tested object plus 1000V as the standard voltage. The test voltage of some products may be higher than this specified value. According to iec61010, the test voltage must gradually rise to the required test voltage value (such as 5kV, etc.) within 5S to ensure that the test voltage value is stably added to the tested insulator for no less than 5S. At this time, the leakage current value of the measured circuit can be compared with the leakage current threshold specified in the standard to judge whether the insulation performance of the tested product meets the standard.

After the test, the test voltage must be gradually reduced to zero within the specified time. During the withstand voltage test, the measurement standards are different for the tested objects with different technical specifications. For the general tested equipment, the withstand voltage test is to measure the leakage current value between the live wire and the shell. The basic requirement is: double the working voltage of the tested object plus 1000V as the standard voltage. The test voltage of some products may be higher than this specified value. According to iec61010, the test voltage must gradually rise to the required test voltage value (such as 5kV, etc.) within 5S to ensure that the test voltage value is stably added to the tested insulator for no less than 5S. At this time, the leakage current value of the measured circuit can be compared with the leakage current threshold specified in the standard to judge whether the insulation performance of the tested product meets the standard. After the test, the test voltage must be gradually reduced to zero within the specified time.

It is a test to judge whether the insulation material and space distance of the equipment meet the requirements by giving the equipment a voltage higher than its rated voltage and maintaining it for a certain time. Voltage withstand test is an important part of electrical safety standard, which is used to find local defects, moisture and aging of product insulation.