How to eliminate interference problems in partial discharge tester testing:
(I) External interference
1. Interference unrelated to power supply voltage
This type of interference is unrelated to the power supply voltage (the voltage applied to the test object) and does not change with the increase or decrease of the power supply voltage. It is generated by: opening and closing operations of electrical switches, welding arc striking, crane operation, brushes of rectifier motors, flash lamps, radio electromagnetic waves, and various industrial interferences, etc. These interferences invade through paths such as the power supply, test circuit, and ground wire.
2. Interference related to power supply voltage
This type of interference generally increases with the increase of power supply voltage. It can be generated by various parts in the test area. For example: test transformer, high-voltage lead wire, end of test object, poor contact of high-voltage line, contact between insulating objects in the high-voltage test area and the ground wire (or grounded metal objects), poor grounding of metal objects in the test area, and induced discharge of other objects, etc. The invasion paths of interference related to power supply voltage can invade the test circuit through the power supply, high-voltage conductor, space, and ground wire.
(II) Methods for eliminating external interference in partial discharge testers
1. Methods to eliminate interference unrelated to power supply voltage: Measures should be taken from aspects such as power supply, space, and grounding method. To eliminate space electromagnetic wave interference, the test room should be shielded. For interference invading from the power supply, isolation transformers and filter devices are generally added at the power inlet. To eliminate interference from the grounding grid, a single-point grounding method should be adopted.
2. Measures to eliminate interference related to power supply: The high-voltage lead wire can be thickened (using thicker corrugated pipe, thin iron sheet cylinder, or aluminum cylinder); anti-corona shields should be added to the ends of the test object; all ground wires and metal objects in the test area should be well grounded; insulating objects in the test area are strictly prohibited from contacting metal grounding bodies; there should be no metal objects such as screws or ground wire ends on the ground below the high-voltage line.
