The partial discharge detector (abbreviated as partial discharge tester) is the "stethoscope" for diagnosing the insulation status of high-voltage electrical equipment. It is mainly used to detect internal insulation defects in transformers, GIS, switchgear, cables, instrument transformers, and other equipment. It is core equipment for preventive testing, handover acceptance, and condition-based maintenance in the power sector.
Core Working Principle
When partial discharge occurs, it generates multiple physical signals. The mainstream detection technology routes include:
Detection Method Frequency Band Principle Applicable Equipment
Pulse Current Method (ERA) 10kHz～500kHz Measures pulse current through coupling capacitance, can quantitatively read discharge magnitude (pC) Laboratory/factory testing, transformers/cables
Ultra-High Frequency Method (UHF) 300MHz～3GHz Captures GHz-level electromagnetic waves generated by partial discharge, strong anti-interference capability GIS, transformers, switchgear
Acoustic Emission Method (AE) 20kHz～300kHz Receives acoustic signals generated by discharge, can assist localization Switchgear, transformer exterior
Transient Earth Voltage Method (TEV) 3MHz～100MHz Detects transient voltage response on metal cabinet surfaces Rapid screening of switchgear
High-Frequency Current Method (HFCT) 3MHz～30MHz Clamp-type sensor collects high-frequency pulses from grounding wires Cable body and accessories
Multi-mode fusion is the mainstream trend: a single method carries the risk of missed detection. Handheld devices generally integrate UHF+TEV+AE+HFCT, and through multi-signal cross-validation, the defect detection rate is increased to over 95%.
Core Selection: Match by Application Scenario
1. Factory Testing and High-Precision Diagnosis (Offline Quantitative)
Detection Sensitivity ≤0.1pC (laboratory conditions)
Sampling Rate ≥100MS/s, accuracy 14bit
Dynamic Range ≥70dB (high-end 120dB)
Number of Channels Multi-channel synchronization (6 or more channels), supports fiber-optic synchronization
Standards Compliance IEC 60270, GB/T 7354, calibration certificate required
Recommended route: Multi-channel pulse current method system, suitable for transformer/GIS factory handover and post-overhaul diagnosis, with traceable results.
2. Daily Inspection of Switchgear and Distribution Rooms (Live Inspection)
Detection Method TEV+UHF+AE multi-mode fusion
Weight ≤1.5kg, single-person operation
Battery Life ≥8 hours
Synchronization Method Internal synchronization + wireless synchronization (≥50m)
Protection Rating IP54 and above
Recommended route: Handheld multi-mode partial discharge tester, can screen hidden dangers without opening the cabinet, TEV rapid general survey + AE/UHF recheck and localization.
3. Multi-Point Inspection of GIS/Transformers/Cables (Preventive Testing)
Detection Method UHF+HFCT+AE combination
Multi-Unit Cascading Supports distributed synchronous acquisition
Wireless Transmission ≥1000m
Spectrum Analysis PRPD/PRPS spectra, AI defect recognition
Recommended route: Multi-function integrated partial discharge tester, supports multi-unit cascading to piece together a full-area view, suitable for substation preventive testing.
4. Long-Cycle Online Monitoring (Trend Monitoring)
Sensor Fixed three-in-one (HFCT+AE+UHF)
Communication Protocol IEC 61850/Modbus, 4G/5G/fiber optic
Protection Rating IP65 and above
Operating Temperature -40℃～+70℃
Recommended route: Fixed online monitoring device, long-term resident to capture early defects, data uploaded to the cloud for trend analysis.
Parameter Item Handheld Portable Type Benchtop/Multi-Channel System Online Monitoring Type
Detection Sensitivity ≤10pC (on-site) ≤0.1pC (laboratory) ≤50pC
Sampling Rate 50～200MS/s 100MS/s～2GS/s —
Dynamic Range 70dB 120dB —
Detection Frequency Band Multiple selectable ranges 10kHz～3GHz full coverage Determined by sensor
Number of Channels Single/dual channel 6～960 channels 3 channels
Data Storage 500～1000 sets More than 2000 sets Cloud storage
Overall Weight 0.7～3.5kg 10～30kg Sensor <1kg
Battery Life 8 hours External power supply External power supply
Essential Function Checklist (Hard Procurement Indicators)
Multi-detection method fusion: At least supports TEV+AE; high-end models integrate UHF+HFCT; a single method has a high risk of missed detection
PRPD/PRPS spectrum analysis: Phase-resolved partial discharge spectra are the core basis for determining discharge type (corona/floating/void)
Digital filtering and anti-interference: Hardware filtering (high-pass/low-pass/band-pass) + software algorithms (wavelet denoising/adaptive noise reduction), on-site signal-to-noise ratio ≥10:1
Multi-unit cascading and wireless synchronization: Essential for long-distance GIS/cable detection; wireless transmission distance ≥1000m is practical
Data export and report generation: Supports USB/Bluetooth/WiFi export, with PC software to generate Word reports
Calibration and traceability: Pulse current method equipment requires a calibration pulse generator and calibration certificate
Background noise recording: Record the environmental baseline before testing; signals below noise by 3dB are considered invalid
Headphone monitoring function: Real-time monitoring of discharge signals in ultrasonic mode to assist judgment
Local and Mainstream Manufacturer Resources
Yangzhou Local Manufacturers (Nearby Connection, Fast After-Sales Response)
A Jiangsu Province "Specialized, Refined, Distinctive, and Innovative" enterprise, participated in formulating the DL/T 846.4 partial discharge detector industry standard and GB/T 16927.1 national standard. Products cover partial discharge detectors, power-frequency partial-discharge-free test transformers, partial discharge test shielding rooms, and other complete equipment. 49 patents + 7 software copyrights, with deep technical heritage.
Mainly engaged in the R&D, production, sales, and on-site installation and maintenance of partial discharge equipment, while also providing partial discharge/infrared/ultraviolet/ultrasonic testing services for power equipment, with complete capabilities from equipment to testing services.
A high-tech enterprise, with product lines covering partial discharge detection systems, transformer comprehensive test benches, etc., serving the power/communications/railway/petrochemical and other industries.
KJF2002 partial discharge detector, using high-frequency pulse current method (ERA), sensitivity 0.02pC, amplifier frequency band with multiple selectable ranges, pointer + digital dual-meter display, suitable for quantitative testing of motors/transformers/cables.
TPJFC-C handheld switchgear partial discharge detector, integrating TEV+ultrasonic, color LCD screen, effective detection distance 15m, with headphone monitoring and laser aiming localization, suitable for daily inspection of distribution rooms.
Jiangsu Flir Infrared Measurement and Control Technology Co., Ltd. (Development Zone Zhigu Technology Complex): Mainly engaged in the sales and maintenance of partial discharge testers and technical services for switchgear/GIS/cable partial discharge testing, while also acting as an agent for imported power construction machinery.
Partial discharge detection sensitivity 1pC, intelligent noise reduction system can filter over 99% of interference, passed CNAS laboratory certification and EU CE certification, 8 major warehousing service centers nationwide, technical team arrives on site within 48 hours.
Its predecessor was the High-Voltage Test Equipment Manufacturing Plant of Wuhan High Voltage Research Institute (1992). In 2025, it obtained the invention patent for "Integrated Partial-Discharge-Free Withstand Voltage Test Device and Partial Discharge Detection Method," with winning bid records from multiple provincial companies of State Grid/China Southern Power Grid.
The partial discharge inspection instrument integrates acoustic imaging + multi-principle partial discharge + infrared thermal imaging, with an overall weight of 1.3kg and 7-hour battery life, lifetime maintenance for the entire series + 24-hour technical response, and repeat purchase records from old customers in Wuxi, Jiangsu in 2026.
KVPD partial discharge complete equipment, KVZJF partial discharge inspection instrument, matched with partial-discharge-free power-frequency withstand voltage test devices, providing comprehensive solutions for transformer test stations.
Products cover partial discharge detection equipment, transformer detection equipment, etc., with customers across provincial and municipal power/steel/petrochemical enterprises.
Other Well-Known Domestic Brands
Beijing Kanggaote (KGT): Representative of the domestic multi-mode fusion route. The "Jinzha" handheld type (UHF+HF+AE+TEV+VDS) is suitable for switchgear inspection, while the "Nezha" multi-function type extends to GIS/transformers/cables, supporting multi-unit cascading + data cloud upload.
Austrian OMICRON: Imported benchmark of the MPD series, 14-bit ADC/64MS/s sampling, background noise <0.015pC, fiber-optic synchronization channel spacing up to 2km, suitable for laboratory-grade high-precision diagnosis and large-scale factory testing.
UK EA Technology: Pioneer of TEV technology. The UltraTEV series has a built-in health scoring system, suitable for large-scale standardized daily inspection.
Implemented Standards
GB/T 7354-2018: High-voltage test techniques - Partial discharge measurements (current national standard)
IEC 60270: International standard for partial discharge measurement
DL/T 846.4-2016: General technical specifications for high-voltage testing equipment - Part 4: Partial discharge measurement
DL/T 417-2019: Guide for on-site measurement of partial discharge in power equipment
DL/T 596-2021: Preventive test code for electric power equipment
DL/T 1630-2016: Technical specification for UHF partial discharge detection of gas-insulated metal-enclosed switchgear
Precautions for Use
The pulse current method must be calibrated first: Before testing, use a calibration pulse generator to inject a standard charge amount and confirm system sensitivity
Record background noise first: Before formal testing, record the environmental baseline; signal amplitude below noise by 3dB is considered invalid
Cross-validate with multiple sensors: Abnormalities in a single channel need to be rechecked with other methods to avoid misjudgment
Maintain a safe distance during live detection: Use insulating rods and strictly comply with safety regulations
Combine PRPD spectra with load analysis: Repeatedly measure the same measuring point under different loads/temperatures to establish a trend file
Pay attention to cabinet structure in UHF detection: Metal shielding attenuates signals, and sensor position directly affects detection results
