Partial Discharge Tester, often referred to as PD Detector



is a core precision instrument used in power systems to detect whether there are partial discharge defects inside the insulation of high-voltage electrical equipment.

Its core function is to accurately assess the insulation health of high-voltage equipment such as transformers, cables, and switchgear by capturing various weak signals (such as electrical pulses, electromagnetic waves, ultrasonic waves, etc.) generated by partial discharges in the insulating medium, thereby detecting and locating hidden dangers before equipment breakdown occurs.

Currently, mainstream PD testers generally adopt multi-sensor fusion and digital anti-interference technology, featuring high sensitivity, strong anti-interference capability, and intelligent pattern recognition functions.

The following is a detailed introduction to the core principles, functions, and technical characteristics of such instruments:

⚡ Core Working Principle

When air gaps, impurities, or defects appear inside the insulation of high-voltage equipment, local, non-penetrating discharges can occur under the influence of an electric field. PD testers mainly capture these discharge signals through the following principles:

Pulse Current Method (IEC 60270 standard): This is the most classic quantitative detection method. By using coupling capacitors and detection impedances, the pulse current signals generated by partial discharges are picked up, and after amplification and filtering, the apparent discharge quantity (in picocoulombs, pC) is accurately measured.

Ultra-High Frequency Method (UHF): Partial discharges excite ultra-high-frequency electromagnetic waves with frequencies ranging from 300MHz to 1500MHz. UHF sensors can effectively capture these signals, making them particularly suitable for detecting GIS (Gas-Insulated Switchgear) and transformers, with strong resistance to low-frequency interference.

Acoustic Emission Method (AE): The transient pressure waves generated by discharges radiate ultrasonic waves outward. Through contact or non-contact ultrasonic sensors, these acoustic signals can be captured and are often used for precise spatial location of discharge sources.

Transient Earth Voltage Method (TEV): Mainly used for detecting metal-enclosed equipment such as switchgear. The electromagnetic waves generated by discharges induce currents on the inner surface of the metal enclosure and propagate outward to form transient earth voltages, which can be detected on the surface of the equipment enclosure using magnetic-capacitive coupling sensors.