Wuhan Xinsheng Neng recommends the ultra low frequency high voltage generator, which is generally used for the withstand voltage test of power cables, and also for the insulation withstand voltage test of large power transformers.
It is characterized by no damage to the tested cables, and it can also test the cables that are starting to aging but can still be used, so it is a no-damage voltage test method.
This test is more accurate than the DC high voltage test in determining the connection errors of new and repaired cables at their joints and end heads.
Industry standard "Ultra-Low Frequency (0.1Hz) Voltage Test Method for xLPE insulated power Cables up to and including 35kV". According to the requirements of this industry standard, the test procedures are as follows:
All the electrical equipment connected with the test product shall be separated from the test cable, and the test equipment (ultra-low frequency high voltage generator, etc.) shall be reliably grounded by bare copper wire.
Use 10000V megohm meter to test the insulation resistance of each phase of the test cable, and record the test value.
Test voltage peak: 3VO, test time: 60min.
When the capacitance of the test cable is within the load capacitance capacity of the test equipment, the three-phase core of the test cable can be connected in parallel and the voltage withstand test can be carried out at the same time.
Connect the test equipment with the test cable with a flexible connection cable, turn on the power supply, and start the voltage boost test. During the process of voltage boost, the high voltage circuit should be closely monitored, and the test cable should be monitored for abnormal sound. When it rises to the test voltage, it begins to record the test time and read the test voltage.
After the test time, first reduce the voltage to zero, and then cut off the power supply. If no destructive discharge occurs in the test, it is considered to have passed the voltage test.
Voltmeter are generally found in the process of pressure and pressure pointer swing is bigger, ammeter indicates a sharp increase in voltage regulator to step-up voltage basic stagnating or declining, and the current increasing amplitude is bigger, try the cable emits an odor, smoke or abnormal phenomenon such as a sound or flash flipping, should immediately stop the booster, step-down power cuts after find out the reason. If these phenomena are found to be caused by the weak insulation part of the test cable, it is considered that the voltage test is not qualified. If it is determined that the test cable is caused by air humidity or dirty surface, the test cable should be cleaned and dried before testing.
During the test, if the test is interrupted due to unexpected loss of power supply due to non-test cable insulation defects, the full time connection should be re-established after the cause is found and the power supply is restored.
