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Detection Technology

Interference partial discharge detector

time:2020/9/2   source:华天电力  reading:292 time

The various interferences in the test will reduce the detection sensitivity of the partial discharge test. During the test, the interference level should be suppressed to the lowest level. Interference types usually include: power supply interference, grounding system interference, electromagnetic radiation interference, discharge interference of various components of the test equipment, and various contact interference.

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1. Suspended potential discharge interference. The induced floating potential discharge caused by ungrounded metal objects adjacent to the test circuit is also a common interference. Its characteristic is that it increases with the increase of test voltage, but its waveform is generally easier to identify. The countermeasures for elimination are moving away and grounding.

2. The interference of corona discharge and contact discharge at each connection. Corona discharge occurs in the conductive parts of the test circuit at high potential, such as the flanges, metal caps, test transformers, coupling capacitor ends, and high-voltage leads of the test sample. In the test circuit, the contact discharge interference will also occur due to the poor contact of each connection. The characteristics of these two interferences increase with the increase of the test voltage. Elimination of this interference is to adopt anti-corona measures (such as anti-corona ring, etc.) at the high-voltage end, use a corona-free conductive round tube for the high-voltage lead, and ensure good contact between the connections.

3. Test the internal discharge interference of transformer and coupling capacitor. This discharge is easily confused with the internal discharge of the sample. Therefore, the partial discharge level of the test transformer and coupling capacitor used should be controlled below a certain allowable amount.

4. Power interference. The power supply used by the detector and the test transformer is connected to the low-voltage distribution network, and various high-frequency signals in the distribution network can directly cause interference. Therefore, shielded power isolation transformers and low-pass filters are usually used for suppression, and the effect is very good.

5. Grounding interference. The test loop grounding method is improper. For example, in a grounding grid system with two points or more grounded, various high-frequency signals will be coupled to the test loop via the grounding wire to cause interference. This interference generally has nothing to do with the test voltage. One point grounding is used for the test circuit to reduce this interference.

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