Partial discharge（PD） is a pulsed discharge that produces a series of physical phenomena and chemical changes such as light, sound, electrical and mechanical vibrations in and around electrical equipment. When insulation defects occur in high-voltage electrical equipment, partial discharge signals will be generated. Through the detection and analysis of these signals, it can be judged whether there are hidden dangers of insulation inside the high-voltage electrical equipment, and the further expansion of potential accidents can be prevented. So regular PD testing is critical as part of a condition-based management (CBM) regime. This enables operators to obtain baseline PD readings to assess insulation quality, locate PD activity and determine maintenance goals

GTPD-92 partial discharge detector developed by our company is a multi-functional hand-held instrument. It is based on TEV, ultrasonic, UHF and high-frequency current(HFCT) detection methods to test the partial discharge of the HV equipment, and can read the partial discharge amplitude and spectrum. The waveform can provide storage and readout functions of two-dimensional and three-dimensional maps, etc., and can better evaluate the partial discharge of electrical equipment. partial discharge detector is suitable for partial discharge detection of electrical equipment such as GIS, switch cabinets, transformers and power cables. The equipment is portable and easy to operate, and all detections do not have any impact on the operation of high-voltage equipment. The product can observe the measurement signal in multiple cycles, identify the frequency of discharge, and analyze it through various modes, which can clearly determine the fault.

The partial discharge detector adopts a brand-new design and uses the currently popular Android system, which is easier to operate and use. In addition, it integrates 5 million pixel cameras to take pictures to facilitate inspection records; RFID is conducive to expanding the application of the Internet of things; internal integration discharge type library is provided to facilitate the comparison and verification of discharge conditions.

GTPD-92 partial discharge tester Technical Specification

Host parameters
Detectable channels	4 Channels 1 TEV 1 US 1 UHF(Wireless, optional) 1 HFCT(Wireless, optional)
Sampling accuracy	12bit
synchronous mode	Internal synchronization, external synchronization, and photosynchronization
TEV
Detecting bandwidth	3M-100MHz
Detecting range	0～60dB
Detecting deviation	±2dB
resolution	1dB
Max.number of pulses per cycle	720
Mini. Pulse frequency	10Hz
Output interface	Standard SMA connection host
Non-contact US
Center frequency	40kHz
Resolution	0.1uV
Accuracy	±0.1uV
Detecting range	0.5uV～1mV
Output interface	Standard SMA connection host
Contact US
Center frequency	20kHz～300kHz
Resolution	50 Ω
Accuracy	0.1mV
Detecting range	0.1mV～1V
Output interface	Standard SMA connection host
UHF(optional)
Detecting bandwidth	300MHz～1.5GHz
Output mode	BNC interface-Signal conditioning unit, wireless connection to the host
Receive mode	Antenna receive
Transmission mode	Coaxial cable
Detecting sensitivity	≤60dBm
HFCT(optional)
Detecting bandwidth	1M-30MHz
Transfer impedance	>5mV/mA (10MHz )
Output impedance	50 Ω
Detecting range	-20~80dB
Detecting deviation	±1dB
Accuracy	1dB
Output interface	BNC Interface-Signal conditioning unit, wireless connection to the host
Hardware
Display screen	A 5.0-inch TFT True color LCD screen
Resolution	800×480
Operation mode	Touch / button
Storage	TF Card
Sound interface	3.5 mm Stereo headphone jack
Power	DC-12V/2A DC Power
Extended function	USB-Type/500Mega pixel camera/RFID/Wi-Fi/Bluetooth
Power
Internal Power	battery powered（4800mAH 7.4V）
Working time	About 7 hours, and the filling time is about 3 hours
Dimension
L×W×H	235 mm×133 mm×48 mm
Weight	0.85 kg
Environment
Use ambient temperature	-20℃～50℃
Storage environment temperature	-40℃～70℃
Humidity	10%-90%（Non-condensation）
Height above sea level	≤3000 m

GTPD-92 partial discharge tester Operation Interface

Infrared Thermography,UHF,TEV,HFCT,Ultrasonic sensors: Which test tells you more in PD Testing?

Infrared Thermography (IRT) and Partial Discharge (PD) testing are two widely adopted condition monitoring techniques in modern power systems, each with distinct applications and technical strengths. IRT detects surface temperature anomalies to identify potential faults caused by increased electrical resistance, such as loose connections, overloads, or deteriorated contacts. Based on passive thermal radiation measurement, IRT is simple to operate, allows for non-intrusive and live inspections, and is particularly effective for components like switchgear, busbars, and cable terminations. However, it has notable limitations: it can only detect faults that produce significant heat and cannot identify early-stage insulation degradation or internal defects. The results are also influenced by ambient temperature, surface emissivity settings, and operator experience. In contrast, PD testing detects small electrical discharges occurring within or on the surface of insulation systems. These discharges often indicate the onset of insulation breakdown, such as voids, cracks, surface contamination, or moisture ingress, allowing for much earlier detection of critical insulation failures.

PD testing employs various sensor technologies, including Ultra High Frequency (UHF), Transient Earth Voltage (TEV), High-Frequency Current Transformers (HFCT), and ultrasonic sensors. These systems analyze signal amplitude, phase, repetition rate, and waveform characteristics to assess discharge severity and type. PD signals typically exhibit short-duration, high-frequency pulses, and can propagate through metallic enclosures, making them suitable for metal-clad medium-voltage equipment. TEV measurements are effective for detecting internal discharges, while ultrasonic methods are better suited for surface or corona discharges. Unlike IRT, PD testing not only identifies defects before any heat is generated but also supports long-term condition-based monitoring and trending analysis. It is particularly applicable for critical equipment such as cable terminations, ring main units, GIS, and transformer windings. However, PD testing requires more sophisticated instrumentation and trained personnel to distinguish real signals from background noise and to minimize false positives.

According to international standards and industry best practices, IRT and PD testing should be used as complementary techniques. For instance, NFPA 70B in the United States recommends regular infrared and PD inspections for high-voltage equipment (>1000V). Similar guidelines are found in the UK and Australia for substations and critical assets. For metal-enclosed equipment, TEV and ultrasonic PD testing can be performed externally through the panel, while IRT is ideal for detecting heat-related issues in cable connectors, bus joints, and breaker contacts. In older systems or environments with significant electromagnetic interference, combined techniques (e.g., simultaneous TEV and ultrasonic monitoring) enhance diagnostic accuracy and confidence in results.

In summary, IRT is well-suited for identifying resistive faults and surface heating, while PD testing is more effective at detecting internal insulation degradation at an early stage. Integrating both methods enables a comprehensive asset monitoring strategy, combining surface thermal detection with internal dielectric diagnostics. Industry standards recommend joint application, and the reliability of the results depends heavily on the competency of the operators. Certified training (e.g., FLIR Level I/II for thermography or PD specialist training from EA Technology) is strongly recommended. By selecting the appropriate method based on asset type, voltage level, and environmental conditions, utilities and asset managers can significantly improve system reliability and reduce the risk of unplanned outages and catastrophic failures.

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