I. Test Equipment
The test uses a power frequency withstand voltage tester, with a test voltage frequency of (49~61)Hz. The voltage measurement value is kept within ±3% of the specified voltage value. For low-voltage cables, a variable transformer is usually used to generate voltage, while medium and high-voltage cables can also use a series resonance circuit to generate voltage.II. Sample Preparation
Sample Cutting
For 750V and below PVC insulated wire and cable, rubber insulated cable finished cable voltage test sample length is at least 10m, insulated wire core voltage test sample length is at least 5m;
Low-voltage power cable routine test whole reel, type test sample length of (10-15)m.
III. Test Procedure
Wiring Method
The conductor is connected to high voltage, other conductors and metal layers or water are grounded.
Voltage Increase Method
The voltage should start from a sufficiently low value (usually below 40% of the specified applied voltage), then slowly increase the voltage so that it can be accurately read on the meter. When the voltage exceeds 75% of the test voltage, the voltage can be increased at a rate of 2% per second to meet the requirements.
Voltage Reduction Method
The voltage should be reduced to below 40% of the specified test voltage before the power supply can be cut off.
IV. Safety Precautions
(1) The operator of the withstand voltage tester must wear rubber insulating gloves and pad rubber insulating mats to prevent high voltage electric shock; the withstand voltage tester must be reliably grounded.
(2) Before the test starts, the equipment needs to be functionally checked to ensure that the sample breakdown equipment can be powered off.
(3) During the test of the withstand voltage tester, the grounding terminal of the instrument and the test body must be reliably connected, and open circuit is strictly prohibited.
(4) Once the test lamp and alarm of the withstand voltage tester are damaged, they must be replaced immediately to prevent misjudgment.
V. Test Record
(1) Sample number, sample specifications, model.
(2) Test date, atmospheric conditions.
(3) The value and time of the applied voltage.
(4) Test results.
