I. Classification of Partial Discharge Test Instruments
Based on different detection principles, partial discharge test instruments can be classified into various types, each with its own applicable scenarios and technical features.
Pulse Current Method
As a standard testing method, this approach quantitatively measures the pulse current generated by partial discharge, with results expressed in picocoulombs and high precision. This method requires the connection of the detection circuit when the equipment is de-energized and is mainly suitable for offline testing scenarios such as laboratories and equipment factory tests.
Ultrasonic Method
This method uses sensors to capture the sound wave signals generated by discharge, focusing on the ultrasonic waves that are imperceptible to the human ear. It has strong resistance to electromagnetic interference and can physically locate the discharge point, making it suitable for on-line inspection when the equipment is in operation, and can detect surface discharge phenomena of the equipment.
Transient Ground Voltage Method
This method is mainly used for switchgear detection. When partial discharge occurs inside the switchgear, electromagnetic waves will induce a transient voltage on the metal cabinet surface. By detecting this voltage signal, internal insulation defects of the switchgear can be quickly screened, making it the mainstream technology for on-line inspection of switchgear.
UHF Method
This method detects the ultra-high frequency electromagnetic wave signals generated by discharge, with a frequency range typically between 300 MHz and 3 GHz. This frequency band can effectively avoid common interference such as corona in the air, and has the characteristics of strong anti-interference ability and high sensitivity. It is suitable for internal discharge monitoring and location of gas-insulated switchgear, transformers, and other enclosed equipment.
High-Frequency Current Method
This method couples the high-frequency current signals generated by discharge by clamping a high-frequency current transformer on the grounding wire or the body of the power cable. It is mainly used for on-line detection and monitoring of power cables and their accessories, and can effectively identify insulation problems in the cable body and joints.
II. Practical Application of Partial Discharge Test Instruments
Instruments with different detection principles have clear divisions of labor in practical applications and are suitable for different testing scenarios.
In the factory tests of power equipment and precise measurement work in laboratories, the pulse current method partial discharge test instrument is the recommended equipment, which can precisely quantitatively analyze the apparent discharge quantity of the equipment and provide accurate data for the assessment of equipment insulation performance.
In the daily operation and maintenance of substations, for enclosed high-voltage equipment such as gas-insulated switchgear and transformers, the UHF detection technology is the core. Maintenance personnel can use handheld UHF partial discharge test instruments for inspection or install on-line monitoring systems to continuously monitor the internal insulation status of the equipment.
For the daily on-line inspection of switchgear, the handheld partial discharge test instrument integrating the transient ground voltage method and the ultrasonic method is highly applicable. The transient ground voltage function can quickly scan the surface of the cabinet, and the ultrasonic function can precisely locate abnormal points. The combination of the two methods can effectively improve the inspection efficiency.
For the condition monitoring of power cables, the high-frequency current method is the main approach. By installing sensors on the grounding wire or terminal of the cable, weak discharge signals from the cable body and joints can be captured, providing a basis for the assessment of cable operation status and maintenance decisions.
Post time: Mar-12-2026