1. AC power frequency withstand voltage test

1. Operation method of AC power frequency withstand voltage test

(1) Reliably connect the test transformer with the operation box (set) and the test product and accessories. The shell and operating system of the test transformer must be reliably grounded. The high-voltage tail X end of the test transformer and the measurement winding F end must be reliably grounded.

(2) The test personnel have a clear division of labor, clean up the site (if possible, pull up the shielding net), and send a dedicated person to monitor and observe the status of the test product.

(3) Check whether the voltage regulator is in the zero position, whether the input power is normal, and the test product should be clean and absolutely dry.

(4) Before the load test, an airlift test is generally to be carried out. That is, the test voltage is increased to the test voltage when the test product is not connected, various meters are proofread, and the ball gap is adjusted.

(5) Turn on the power, slowly increase the voltage, pay close attention to various meters, when the voltage rises to the test voltage, start timing, after 1 minute, quickly reduce the voltage, after the voltage is reduced to zero, cut off the power, The test product can be replaced or the test can be ended.

(6) In the process of boosting or withstand voltage, if the following abnormal conditions are found, immediately reduce the voltage and cut off the power supply. Stop the test and find out the reason:

① The pointer of the voltmeter oscillates a lot;

② It is found that the insulation is burnt or smoked;

③ There is an abnormal sound in the test product.

2. A complete set of accessories for power frequency withstand voltage

(1) In the power frequency withstand voltage test, Rl should be selected according to the rated capacity of the transformer. For example, when the rated output of the high-voltage side is 100-300mA, 0.5-Ω/N (test voltage) can be used. Water resistance is commonly used as current limiting resistance. The length of the tube can be considered as 150kV/m, and the thickness of the tube should have sufficient heat capacity. (Preparation method of water resistance liquid: use swallow distilled water to add an appropriate amount of copper sulfate to prepare various resistance values).

(2) The setting value of the ball gap is generally 110% to 120% of the test electric tilt. The ball gap protection resistance can be selected at 1Ω/V (test voltage). When the voltage exceeds the setting value of the ball gap, the ball gap discharges. Products play a protective role.

(3) In the power frequency withstand voltage test, the measured voltage on the low-voltage side (instrument voltage) is not very accurate. The reason is that due to the leakage reactance of the test transformer, there must be a voltage drop or capacity rise, which makes the voltage on the test product low The voltage reflected on the instrument on the low-voltage side is higher or higher. In order to accurately measure the voltage applied on the tested product, an RCF resistor-capacitor oscillator is often connected to the high-voltage side to measure the voltage