Partial Discharge (PD) refers to the discharge phenomenon that occurs in local areas within the insulation system of power equipment, which is often an early sign of insulation material degradation. A partial discharge tester is an instrument specifically designed to detect partial discharge phenomena in power equipment. By using a partial discharge tester, power engineers can promptly identify hidden defects in equipment and prevent failures.
Working Principle
The working principle of a partial discharge tester is based on detecting changes in the electromagnetic field generated during partial discharge. When partial discharge occurs, it is accompanied by the emission of electromagnetic waves. These signals are captured by specific sensors, then processed through amplification, filtering, and other preprocessing steps, and finally displayed on a display unit.
Specifically, the detection principles of a partial discharge tester mainly include the following aspects:
Electrical Measurement Method: The most commonly used methods are the pulse current method and the radio interference voltage method. Taking the pulse current method as an example, when a partial discharge occurs in the test object, a transient voltage change is generated at its terminals, producing a pulse current in the circuit composed of the test object, coupling capacitor, and detection impedance. The pulse current generates a pulse voltage across the detection impedance. By collecting, amplifying, and displaying this pulse voltage, basic parameters of partial discharge, especially the discharge magnitude, can be obtained.
Non-Electrical Measurement Method: Detection is performed by measuring non-electrical physical quantities such as thermal effects, optical effects, and acoustic effects generated by partial discharge.
Usage Method
The usage method of a partial discharge tester typically includes the following steps:
Equipment Check: Before use, check the equipment to confirm battery level, date, and time, and verify that all functions are normal.
Signal Check: In the absence of abnormal signals, ensure that the earphones emit a slight, uniform buzzing noise, and that the curve drawing area on the test interface shows the center line aligned with 0dB, with the average value 10dB lower.
Scanning Detection: Hold the instrument and scan the switchgear panel at a constant low speed. When a PD signal is detected, a distinct discharge sound can be heard through the earphones, and the amplitude curve on the screen rises, with both the average and maximum values increasing.
Locate Discharge Point: The inspector can repeatedly measure the target location from different angles to eliminate environmental noise, and use the built-in laser locator of the PD detector to determine the exact location of the discharge point.
Save Results: After confirmation, press the save button on the device screen to store the test results for later management, analysis, and targeted maintenance.
Set Parameters: As needed, set parameters such as output voltage, units, reading settings, discharge count, and sensor.
Adjust Trigger Mode: By default, the multifunctional PD tester host selects the "Auto" mode. If the host does not detect a trigger within a certain period, it forces a trigger.
Technical Parameters
Technical parameters of a partial discharge tester may include:
Frequency Response Range: Typically from several hundred kHz to several MHz.
Sensitivity: Usually between a few picocoulombs (pC) and tens of picocoulombs.
Display: Large LCD screen.
Battery Life: Typically capable of continuous operation for several hours.
Weight: Lightweight and portable.
Anti-Interference Capability: Able to operate normally under a certain level of electromagnetic interference.
Application Scenarios
Partial discharge testers are widely used in the maintenance and fault diagnosis of power equipment, for example:
GIS/GCB and Switchgear: Used to detect PD faults inside GIS/GCB and switchgear.
Transformers: Used to detect PD phenomena inside transformers.
Cables: Used to detect PD conditions in high-voltage cables.
Power Transformers: Used to detect PD conditions inside power transformers.
Motors and Instrument Transformers: Used to detect PD phenomena inside motors and instrument transformers.
Bushings and Capacitors: Used to detect PD conditions inside bushings and capacitors.
Conclusion
As an important tool for power equipment maintenance, the partial discharge tester helps power engineers promptly identify equipment issues, prevent potential failures, and ensure the stable operation of the power system through regular detection of partial discharge phenomena in power equipment. With continuous technological advancement, future partial discharge testers will become more intelligent and portable, further improving detection efficiency and accuracy.
