A Partial Discharge Tester (referred to as “PD Tester”) is a precision instrument used to detect whether “partial discharge” phenomena exist within the insulation system of high-voltage electrical equipment.
If the insulation material is compared to the equipment's “skin,” partial discharge is like tiny “needle-point discharges” or “bubble breakdowns” beneath the skin. Although it does not immediately cause a complete short circuit, long-term partial discharge will gradually corrode the insulation material, much like termites gnawing at wood, eventually leading to severe equipment explosions or power outages.
Therefore, the Partial Discharge Tester serves as a “CT scanner” 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 determine the discharge condition.
Currently, the mainstream detection technologies mainly include the following, each corresponding 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 from 300MHz to 3GHz Strong anti-interference, extremely high sensitivity, and easy to locate. Monitoring internal discharges in GIS (Gas-Insulated Switchgear) and transformers.
Acoustic Emission Method AE Captures mechanical vibration waves generated by discharge Accurate positioning, immune to electromagnetic interference, and allows non-contact measurement. Locating surface discharges on transformers and switchgear.
Transient Earth Voltage Method TEV Measures transient voltage to ground induced on metal enclosures Easy to operate and does not require contact with live parts. Daily inspections of switchgear (ring main units).
High-Frequency Current Transformer Method HFCT Clamps onto grounding wires to measure high-frequency currents Live detection, easy installation, and non-invasive. Online monitoring of cables and transformer grounding wires.
