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Detection Technology

Partial discharge test interference

time:2021/3/31   source:华天电力  reading:776 time

Partial discharge is difficult to avoid for high-voltage electrical products, because the electric field intensity of a certain part is too high. There are two reasons for the high electric field intensity: ①There are bubbles or impurities inside the insulation; ②The electric field near the metal electrode inside the insulation is uneven, and the metal edges have angles or burrs.

The digital partial discharge detector is suitable for the partial discharge detection test of various high-voltage electrical equipment. It has new digital filtering and interference suppression functions, making the user's operation and diagnosis easier and more convenient. Can produce single-channel and dual-channel tests according to customer requirements, with multiple view display modes such as sine and dot matrix, digital filtering and interference suppression functions, combined with rich dynamic statistical analysis maps, so that on-site interference can be more effectively suppressed. Operation and diagnosis are easier.

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1. The form of interference during partial discharge measurement:

(1) Interference from the power supply network;

(2) The interference of various electromagnetic field radiation;

(3) Poor contact of the test circuit, corona at various parts and internal discharge of the test equipment;

(4) Interference of the grounding system;

(5) Discharge of floating potential of metal objects.

Second, the choice of interference suppression measures

There are many interference suppression measures, and it is often impossible to completely eliminate some interference at the substation site. In the actual test, as long as the interference is suppressed below a certain level, the partial discharge inside the sample can be effectively measured. This depends to a large extent on the analytical ability and experience of the tester.

1. Measures to suppress the interference of the power supply network.

1) Power supply filter. Set a low-pass filter on the primary of the high-voltage test transformer to suppress interference in the test power supply network. The cut-off frequency of the low-pass filter should be as low as possible, generally lower than 200-300Hz, and designed to suppress the interference from the two lines of the phase line and the neutral line (such as 220V power supply).

2) Shielded isolation transformer. The test power supply and the power supply for the test instrument are equipped with a shielded isolation transformer to suppress interference in the power supply network.

3) High voltage filter. A high-voltage low-pass filter is set on the high-voltage end of the test transformer to suppress interference in the power supply network.

2. Measures to suppress interference by using instrument functions and selecting wiring methods.

1) Balanced wiring method. Choosing a balanced wiring method can suppress electromagnetic radiation Ir and power interference Is.

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