The VLF hipot tester under Wuhan UHV can help many power workers conduct various power tests more conveniently.
The test results of VLF high-voltage generators are an important reference for determining whether cables can be put into operation, and are widely used in the power industry. This article will introduce the precautions for VLF high-voltage generators during the testing process.
1. Rongsheng effect
Due to the fact that the voltage withstand test process of cables is purely a capacitive load, when using an VLF high-voltage generator for voltage withstand test, the capacitive current generated in the test circuit will generate a certain amount of frequency impedance voltage drop on the winding of the voltage generator. This creates a capacitance rise effect when the actual voltage acting on the test cable is higher, and the longer the length and larger the capacity of the cable, the more obvious the capacitance rise effect. Therefore, when conducting voltage withstand test, it is required to measure the test voltage value on the end side of the cable. During the test, the voltage value must be carefully observed to avoid damage caused by excessive voltage on the test cable.
2. Voltage resonance
The capacitance of the test cable and the voltage generator form a series circuit. When the leakage reactance values of the two are equal or close, series resonance is highly likely to occur, which can also cause a significant increase in the voltage at the end of the test cable. If the voltage is too high, it will endanger the insulation of the test equipment and the test cable. Therefore, according to this special phenomenon, it is required to connect a damping resistor of appropriate capacity at the output end of the cable during the test to weaken the strength of voltage resonance and ensure that the tested cable or equipment does not suffer from excessive voltage damage.
3. Correct use of voltage measuring instruments for experimental equipment
When using VLF high voltage generators for withstand voltage testing, the measured voltage value cannot be based on the effective voltage data. A peak voltage meter must be used to measure the ultra-low frequency withstand voltage test voltage. This is a must be noted in order to truly reflect the highest voltage that the tested cable can withstand. So as to protect the tested cable or equipment from damage.
4. Safety protection measures for experimental operations
During the experimental operation, the operators must wear labor safety protective equipment and take corresponding safety protection measures. In all metal conductive parts that the human body will come into contact with, as well as the grounding of the testing equipment and the tested cable, a dedicated grounding wire must be used for reliable connection and confirmed to be correct before operation. A warning line should be set up in the work area to prevent harm to other personnel.
5. Precautions for relay protection circuit of experimental equipment
In the relay protection circuit of the test equipment, the power lines used for the control power supply and measuring instruments must be well isolated from the main circuit to prevent damage to the instrument and control circuit components caused by flashover or breakdown of the test cable.
