Partial discharge tester detects extremely weak partial discharges in insulation systems



A partial discharge tester (referred to as "PD tester") is a "precision physical examination instrument" and "early warning system" for the insulation health of power equipment. Its core function is to capture extremely weak partial discharge (PD) signals in the insulation systems of high-voltage electrical equipment (such as transformers, cables, switchgear, etc.), thereby detecting hidden dangers of insulation degradation before serious breakdown faults occur.

Simply put, partial discharge is like tiny "electric sparks" generated inside the insulation layer. Although it does not immediately cause equipment short circuits, long-term partial discharge will continuously corrode insulation materials and eventually lead to major accidents. The task of the PD tester is to keenly "hear" or "see" these weak signals.

⚡ Core Detection Technologies (Multi-dimensional Sensing)

Since partial discharge generates various physical signals such as electrical, acoustic, and optical, modern PD testers typically integrate multiple detection technologies to adapt to different equipment and field environments:

Pulse Current Method (Traditional Quantitative Standard): This is the oldest and most mature method (compliant with IEC 60270 standard). It captures pulse current signals generated by discharges through coupling capacitors, enabling precise measurement of discharge magnitude (usually in picocoulombs, pC). It is mainly used for quantitative analysis in laboratories or factory acceptance tests.

Ultra-High Frequency Method (UHF, Strong Anti-interference): Partial discharges radiate UHF electromagnetic waves from 300MHz to 3GHz. UHF sensors are specifically designed to capture these signals. Since common field interferences like corona and welding have lower frequencies, the UHF method offers strong anti-interference capability, making it particularly suitable for internal detection of gas-insulated switchgear (GIS) and transformers.

Transient Earth Voltage Method (TEV, Ideal for Switchgear Inspection): When partial discharge occurs inside switchgear, electromagnetic waves penetrate through gaps in the metal enclosure, generating transient earth voltages on the cabinet surface. TEV sensors can be attached to the cabinet surface for non-contact detection, making them very suitable for routine live quick inspections of high-voltage switchgear up to 35kV.

Acoustic Emission Method (AE, Precise Location): Discharges generate mechanical vibrations and emit ultrasonic waves. By using contact or non-contact ultrasonic sensors to receive these acoustic signals, not only can discharges be detected, but also precise spatial location of discharge points can be achieved using time differences in sound propagation, completely unaffected by electromagnetic interference.