How to eliminate interference problems in partial discharge tester testing:
(I) External interference
1. Interference unrelated to the 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: the 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 the power supply, test circuit, and ground wire paths.
2. Interference related to the power supply voltage
This type of interference generally increases with the increase of the power supply voltage. It can be generated by various parts in the test area, such as: test transformer, high-voltage leads, ends of the test object, poor contact of high-voltage lines, 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 the power supply voltage can invade the test circuit through the power supply, high-voltage conductors, space, and ground wire.
(II) Methods for the partial discharge tester to eliminate external interference
1. Methods to eliminate interference unrelated to the power supply voltage: Measures should be taken from the aspects of power supply, space, and grounding methods. To eliminate interference from space electromagnetic waves, 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 the power supply: The high-voltage leads can be thickened (using thicker corrugated pipes, thin iron sheet cylinders, or aluminum cylinders); 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 grounded metal bodies; there should be no metal objects such as screws or ground wire ends on the ground below the high-voltage lines.
