Classification And Field Application Of Partial Discharge Testers

The partial discharge tester is a crucial instrument for evaluating the insulation condition of high-voltage electrical equipment. To assist you in comprehensively understanding and making an appropriate choice, I will provide a detailed introduction from the aspects of classification, application, and selection.
Firstly, based on the differences in detection principles, partial discharge testers can be classified into the following categories. Each of them has its own applicable scenarios and technical characteristics.
The pulse current method is a standard testing method recommended by the International Electrotechnical Commission. It achieves quantitative measurement by detecting the pulse current generated by partial discharge. The results are expressed in picocoulombs and have high accuracy. However, since it requires connecting the detection circuit while the equipment is off, this method is mainly applied in offline detection scenarios such as laboratories and equipment factory tests.
The ultrasonic method utilizes sensors to capture the acoustic wave signals generated during discharge, especially the ultrasonic waves that are inaudible to the human ear. Its significant advantage is its strong resistance to electromagnetic interference, and it can physically locate the discharge point, making it highly suitable for equipment inspection while the equipment is in operation. It is also capable of detecting discharge phenomena on the equipment surface.
The transient voltage method is specifically used for detecting switch cabinets. When local discharge occurs inside the cabinet, electromagnetic waves will induce a transient voltage on the surface of the metal cabinet. By detecting this voltage signal, the internal insulation defects of the switch cabinet can be quickly screened out. It is currently the mainstream technology for live inspection of switch cabinets.
The ultrahigh frequency method detects the ultra-high frequency electromagnetic wave signals triggered by discharges. The frequency is usually between 300 MHz and 3 GHz. Because the signals in this frequency range can effectively avoid common air disturbances such as corona, it has strong anti-interference ability and high sensitivity, and is particularly suitable for monitoring and locating internal discharges in enclosed equipment such as gas-insulated switchgear and transformers.
The high-frequency current method couples the high-frequency current signals generated by discharge by installing high-frequency current transformers on the grounding wire or the body of the power cable. This method is mainly used for live detection and online monitoring of power cables and their accessories, and can effectively identify insulation problems in the cable body and at the joints.
Ultrasonic Partial Discharge Detector
In practical applications, these methods have clearly defined roles and responsibilities.
In the factory tests and laboratory precision measurements of power equipment, the pulse current method local discharge tester is the preferred choice. It can conduct precise quantitative analysis of the apparent discharge quantity of the equipment, providing accurate data support for the assessment of the equipment's insulation performance.
In the daily operation and maintenance of substations, for enclosed high-voltage equipment such as gas-insulated switchgear and transformers, ultra-high frequency detection technology plays a crucial role. Maintenance personnel can conduct inspections using handheld ultra-high frequency partial discharge testers, or they can install online monitoring systems to keep track of the insulation status of the equipment in real time.
The daily live-line inspection of switch cabinets places greater emphasis on efficiency and convenience. At this time, a handheld partial discharge tester that integrates transient ground voltage method and ultrasonic method is very practical. The transient ground voltage function can quickly scan the surface of the cabinet, while the ultrasonic function can precisely locate the abnormal points that are detected. The combination of the two can effectively improve the inspection efficiency.
For the condition monitoring of power cables, the high-frequency current method plays a crucial role. By installing sensors on the grounding wire or terminals of the cables, it is possible to effectively capture the weak discharge signals at the cable body and joints, providing a basis for the assessment of the cable's operating status and the decision-making for maintenance.