Insulating tools and safety equipment are indispensable tools and appliances for electrical maintenance, live operation, and live inspection. To ensure the safety of personnel engaged in operation and maintenance as well as live work, it is necessary to conduct acceptance tests on newly used insulating tools and safety equipment.
Electrical test items: Insulation resistance measurement, power frequency AC withstand voltage test.
Measurement of insulation resistance
For the measurement of insulation resistance on the surface of insulating tools, a 2500V megohmmeter should be used. During the measurement, the test electrodes (with a width of 2 cm) at the “L” and “E” terminals of the megohmmeter can be placed about 2 cm apart, and then moved parallelly to cover the entire effective surface. During this process, continuously rotate the meter (or the electric megohmmeter should continue to work), and the insulation resistance value should remain unchanged. Under normal temperature and humidity conditions, the measured insulation resistance value should not be lower than 700 MΩ.
Power frequency alternating current withstand voltage test
The test voltage for insulating tools is determined based on the possible operating overvoltage values that the tools may encounter, with an additional 10% margin. The test voltage is set at 1.1 times the larger working voltage in the system, and the insulating tools are subjected to a withstand voltage test.
The operating overvoltage of the 6-10kv system is considered at 4 times the line voltage. The test voltage is: 4 x 10 x 1.1 = 44kV.
The operating overvoltage of the 35kv system is considered at 4 times the phase voltage. The test voltage is: 89kV.
When applying the test voltage to the effective insulation length of the insulating tool, it is often limited by the test equipment. Due to the high test voltage, the test should be conducted in segments. At this time, the test voltage per centimeter of the insulating length of the tool should be increased by 20% based on the above calculation value. Thus, the test voltage value that should be added per centimeter length can be calculated according to the minimum effective insulation length of the insulating tool.
The test method is as follows:
Withstand voltage test for insulating rods, ropes and ladders: Use fine bare copper wire or fine bare aluminum wire as electrodes, wrap them around the test items, and evenly distribute them at equal intervals on all parts (for example, spaced 30 cm apart).
Insulation glove and boot withstand voltage test: Fill the glove and boot with water, with the water surface 5 cm above the upper edge. Place them in a water tank and immerse them in water. Adjust the lifting frame of the water tank according to the different heights of the glove to make the water levels inside and outside the glove the same. Insert the electrodes into the glove and apply pressure. Pay attention to keeping the part of the glove that is exposed above the water surface dry.
Insulation pad type withstand voltage test: Metal plates can be used as electrodes. The distance between the electrodes should be adjusted to be in direct contact with the test sample. The diameter of the electrodes is 2.5mm. The voltage is applied to the two electrode plates. The test sample is pulled through the two electrode plates. All parts that are used should undergo the test. A sufficient distance should be left at the edge to avoid surface discharge during the test.
Clear inspection of the electric discharge voltage of the high-voltage tester: It is advisable to use a test transformer with a relatively small variation in voltage, which is suitable for accurately reading the voltage value. The voltage should be increased uniformly and slowly. When the light is clear and stable, read the indication value of the voltmeter. This voltage is the clear electric discharge voltage. Generally, it should be repeated 2-3 times.
Post time: Mar-10-2026