Partial Discharge Tester (PD Tester) is a diagnostic tool for insulation of high-voltage electrical equipment, serving as a
stethoscope" and "microscope". It can detect tiny discharge phenomena inside the equipment that are invisible to the naked eye but gradually erode the insulation, making it the most effective means to prevent sudden failures in high-voltage equipment (such as transformers, GIS, cables, and generators). By 2026, with the development of power grid equipment towards Ultra-High Voltage (UHV) and the increasing complexity of renewable energy integration, PD testing has evolved from simple "qualitative detection" to a comprehensive diagnostic system of "high-precision positioning + intelligent pattern recognition + online continuous monitoring". 1. Core Principle: Why measure partial discharge? What is partial discharge (PD)? When there are bubbles, impurities, sharp corners, or moisture inside the insulation of high-voltage equipment, the electric field strength at these defects will concentrate. Although the overall insulation is not broken down, tiny repetitive breakdown discharges occur at the defects. Hazards: Electrical corrosion: electrons generated by discharge bombard the insulation material. Thermal effect: local high temperature accelerates insulation aging. Chemical corrosion: produces ozone (
