(1) Standard test circuit, also known as parallel method. It is suitable for the test product that must be grounded.

The disadvantage is that the high-voltage lead-to-ground stray capacitance is connected in parallel with CX, which will reduce the test sensitivity.

(2) Tandem method, which requires the low-voltage end of the test sample to float to the ground.

The advantage is that the transformer inlet capacitance, the high-voltage line-to-ground stray capacitance and the coupling capacitance CK are connected in parallel, which helps to improve the test sensitivity; the disadvantage is that the input unit will be damaged when the sample is damaged.

(3) Balance method test circuit: The two test samples are required to be close, at least the capacitance is the same order of magnitude.

Its advantage is that in the case of strong external interference, better interference suppression effect can be achieved, and the influence of transformer stray capacitance can be eliminated, and large capacitance test can be done; the disadvantage is that two similar samples are required, and when discharge occurs At the time, try to distinguish which sample is discharging.

Due to the limitation of the field test conditions (it is not easy to find two similar samples and ensure that one sample does not discharge), it is difficult to achieve the field balance method. In addition, when the series method is used, if the sample breaks down, It will cause relatively large damage to the equipment, so out of the idea of protecting the equipment, the parallel method is generally used in the field test.

The high-voltage filter can prevent the test product from breakdown during the test and damage other equipment, block the discharge current from entering the test transformer, and can suppress the harmonic interference from the high-voltage power supply. The isolation filter separates the interference of the power supply from the entire test system , Reduce the background interference of the entire test system.