A Partial Discharge Tester (referred to as "PD tester") is a precision instrument used to detect whether there is a "partial discharge" phenomenon inside the insulation system of high-voltage electrical equipment.
If insulation material is compared to the "skin" of equipment, partial discharge is like tiny "needle-point discharge" or "bubble breakdown" under the skin. Although it does not immediately cause an overall short circuit, long-term partial discharge will gradually corrode the insulation material like termites gnawing at wood, eventually leading to serious equipment explosions or power outages.
Therefore, the partial discharge tester is the "physical examination CT machine" for power equipment (such as transformers, cables, and GIS), used to detect hidden dangers before the equipment is completely damaged.
⚙️ Core Working Principle
When partial discharge occurs, it is accompanied by physical phenomena such as electrical pulses, electromagnetic waves, ultrasonic waves, light, and heat. The PD tester captures these signals through sensors to judge the discharge condition.
Currently, the mainstream detection technologies mainly include the following, and different technologies correspond to different application scenarios:
Table
Detection Technology Abbreviation Core Principle Advantages Typical Application Scenarios
Pulse Current Method IEC 60270 Captures charge pulses generated by discharge Most accurate quantification, complies with international standards, and is the "gold standard" for factory tests. Laboratory, factory tests, and commissioning tests (requires power outage).
Ultra-High Frequency Method UHF Receives electromagnetic waves of 300MHz-3GHz Strong anti-interference, extremely high sensitivity, and easy to locate. Discharge monitoring inside GIS (gas-insulated switchgear) and transformers.
Acoustic Emission Method AE Captures mechanical vibration waves generated by discharge Accurate positioning, immune to electromagnetic interference, and can be measured non-contact. Surface discharge location on transformers and switchgear.
Transient Earth Voltage Method TEV Measures transient earth voltage induced on metal enclosures Easy to operate, no need to contact live parts. Daily inspection of switchgear (ring main units).
High-Frequency Current Transformer Method HFCT Clamps on grounding wire to measure high-frequency current Live detection, easy installation, and non-invasive. Online monitoring of cable and transformer grounding wires.
