Online Partial Discharge Tester
An online partial discharge tester (online partial discharge detector/monitoring system) is a professional device used for real-time monitoring of the insulation status of high-voltage electrical equipment. It can continuously collect partial discharge (PD) signals 24/7 while the equipment is in normal operation, and use intelligent algorithms to assess equipment health in real time, achieving a shift from "passive repair" to "active prevention" in maintenance mode. Working Principle
Online partial discharge testers are based on multiple detection principles. Modern equipment typically employs a multi-modal sensor fusion approach, where various technologies complement each other, significantly improving detection rates and positioning accuracy:
High-Frequency Current Transformer (HFCT): Couples PD pulse current signals on cable ground wires through Rogowski coils. It offers strong anti-interference capability and easy installation, suitable for retrofitting live cables without power outage.
Ultra-High Frequency (UHF): Receives electromagnetic pulse signals in the 300MHz to 3GHz band. It provides non-contact monitoring, high detection frequency, strong anti-interference capability, and can locate discharge points. Widely used in substations of 110kV and above.
Acoustic Emission (AE): Uses piezoelectric sensors to capture mechanical vibration signals in the 20kHz to 300kHz band. It excels in resisting electromagnetic interference and is suitable for detecting cable joints, terminations, and other components.
Transient Earth Voltage (TEV): Assesses discharge severity by monitoring millivolt-level transient voltages on the surface of switchgear cabinets. Mainly used in switchgear inspection systems. System Architecture
Online PD monitoring systems typically adopt a four-layer design: "sensing layer - transmission layer - analysis layer - application layer":
Sensing layer: Deploys composite sensor arrays (UHF+AE+TEV+HFCT) with magnetic or rail-mounted non-invasive installation, plug-and-play.
Transmission layer: Supports multiple communication methods such as LoRa, 4G/5G, fiber optics, and Ethernet, ensuring stable data transmission in complex electromagnetic environments.
Analysis layer: Equipped with a deep learning-based discharge pattern recognition engine, automatically generating PRPD/PRPS patterns and distinguishing partial discharges from corona interference, switching operation noise, etc.
Application layer: Through a monitoring platform, it enables equipment health index assessment, graded alarms, trend prediction, and remote operation and maintenance management, supporting viewing on both web and mobile platforms. Key Technical Parameters
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Parameter Typical Range
Detection Sensitivity ≤0.1pC (laboratory) / ≤5pC (online system)
Detection Frequency Band 100kHz～100MHz (HFCT) / 300MHz～3GHz (UHF)
Sampling Rate 100MS/s～200MS/s
Detection Channels 3～6 channels synchronous acquisition
Positioning Accuracy ≤1m (cable scenarios)
Protection Rating IP65 and above
Operating Temperature -40℃～+70℃
MTBF >50,000 hours
Communication Protocol IEC 61850 / Modbus Main Application Scenarios
Power transformers: Monitor insulation degradation of windings and bushings to prevent flashover faults.
GIS equipment: Non-contact detection of internal insulation defects in switchgear.
High-voltage cables: Insulation status monitoring and fault location for cable bodies, joints, and terminations.
Generators/motors: Stator winding insulation monitoring.
Renewable energy stations: Insulation fault early warning for wind/solar inverters and box-type transformers.
Data centers/industrial plants: Scenarios with high requirements for power supply reliability. Equipment Classification
Based on usage, they can be divided into three main categories:
Fixed online monitoring systems: Permanently installed at equipment sites, monitoring 24/7, supporting remote data access and email alarms, suitable for important substations and critical equipment.
Mobile/portable temporary monitoring systems: Plug-and-play, can be quickly deployed without equipment outage, suitable for temporary monitoring, warranty verification, periodic inspections, and similar scenarios.
Handheld live inspection instruments: Multi-sensor fusion design (TEV+UHF+AE+HFCT), supporting live inspections without power outage, quickly screening discharge defects. Major Manufacturers
Domestic Manufacturers
NARI Technology: GIS PD online monitoring system integration and condition assessment software.
Pinggao Group: PIM-9600 UHF PD online monitoring system, passed Q/GDW 10540.5-2025 type tests.
Shaanxi Public Electric: GZPD-01G GIS partial discharge online monitoring system.
TBEA: PDP-SMART portable intelligent PD online detection system, suitable for 66～500kV cables.
Wuhan Zhongyuan Huadian: Multi-sensor fusion monitoring technology, sensitivity ≤50pC.
Wuhan Moen Intelligent Electric: MEJFD-1000 series online partial discharge detector.
Beijing Bodian Xinli: Transformer PD online monitoring system.
Hangzhou Xiazhong Electronics: Switchgear, transformer, and GIS PD online monitoring devices.
International Manufacturers
OMICRON (Austria): MONTESTO 200 mobile monitoring system, PD measurement uncertainty within ±5%.
Siemens Energy (Germany): Synchronous monitoring of UHF + ultrasonic + TEV + SF6 gas decomposition products.
Hitachi Energy (Switzerland/Japan): Station-wide distributed UHF sensor array architecture.
Prysmian (Italy): GIS/GIL monitoring system based on ultra-wideband current sensing and traveling wave positioning technology. Executive Standards
GB/T 7354-2018: Partial discharge measurement
DL/T 1430-2015: Technical guide for live detection of partial discharge in high-voltage electrical equipment
DL/T 417: Guide for on-site partial discharge measurement of power equipment
IEC 60270: International standard for partial discharge measurements
Q/GDW 10540.5-2025: Type tests for PD monitoring equipment in the power industry
