Online Partial Discharge Tester
An online partial discharge tester, typically referring to an online partial discharge monitoring system, is a device capable of performing 7x24-hour uninterrupted monitoring while power equipment (such as switchgear, cables, GIS, transformers, etc.) is in normal operation. By capturing and analyzing partial discharge signals generated by insulation degradation inside the equipment in real time, it enables early warning and assessment of equipment health, driving the shift from "reactive repair" to "proactive prevention" in maintenance strategies.
Core Technologies and Working Principles
Modern online partial discharge monitoring systems generally adopt a multi-modal sensing fusion approach, integrating multiple detection technologies to complement each other, significantly enhancing detection sensitivity, localization accuracy, and anti-interference capability in complex electromagnetic environments.
Ultra-High Frequency (UHF) Method
Principle: Receives electromagnetic wave signals in the 300MHz-1.5GHz frequency band.
Features: High sensitivity (up to 1-5pC), strong anti-interference capability, especially suitable for fully metal-enclosed equipment like GIS. UHF signals attenuate minimally within the GIS chamber but decay rapidly in solid insulation (e.g., XLPE cables), which is advantageous for defect localization.
High-Frequency Current Transformer (HFCT) Method
Principle: Uses high-frequency current transformers clamped onto cable grounding wires or shielding layers to inductively couple partial discharge pulse currents.
Features: Non-contact installation without power outage. Signals can propagate along cables over long distances (up to 1 km or more), allowing a few sensors to cover long cable runs, making it the preferred method for cable system monitoring.
Transient Earth Voltage (TEV) Method
Principle: Monitors millivolt-level transient voltages on the metal enclosure surface of switchgear caused by internal discharges.
Features: Primarily used for switchgear, assessing discharge severity based on signals on the enclosure surface; easy to install.
Acoustic Emission (AE) Method
Principle: Uses piezoelectric sensors to capture mechanical vibration signals in the 20kHz-300kHz frequency band.
Features: Completely immune to electromagnetic interference, often used in combination with UHF or TEV methods for cross-validation and precise localization, effectively reducing false alarm rates.
Typical System Architecture
A complete online partial discharge monitoring system typically comprises the following four layers:
Perception Layer: Deploys various sensors (UHF, HFCT, TEV, AE, etc.) installed non-invasively via magnetic mounts, rails, or through-core methods, without altering the original electrical and mechanical structure of the equipment.
Transmission Layer: Supports multiple communication methods such as fiber optics, Ethernet, 4G/5G, and LoRa, ensuring stable data transmission back to the backend in complex environments.
Analysis Layer: Equipped with intelligent algorithms or expert analysis systems to automatically distinguish partial discharge signals from interference noise such as corona and switching operations, performing discharge pattern recognition, trend analysis, and fault diagnosis.
Application Layer: Through web or mobile monitoring platforms, enables visualization of equipment health status, graded alarms, historical data query, and remote operation and maintenance management.
Main Application Scenarios
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Equipment Type Common Detection Methods Core Advantages
GIS/GIL UHF + AE Extremely high sensitivity to defects such as internal conductor burrs and floating potentials; UHF signals experience low attenuation within metal enclosures.
Power Cables HFCT + AE/UHF HFCT enables long-distance monitoring, suitable for online monitoring of cable joints and terminations; dual-end HFCT can achieve meter-level localization.
Switchgear TEV + UHF + AE Multi-technology fusion effectively overcomes strong electromagnetic interference in switch stations, achieving high-accuracy fault early warning.
Transformers/Motors HFCT + UHF + AE Comprehensive monitoring of insulation status in windings, bushings, and other parts; supports combined online and offline detection.
Key Performance Indicators
When selecting a system, the following technical parameters deserve attention:
Detection Sensitivity: Measures the system's ability to detect weak discharges; for example, UHF method can reach 1-5pC, HFCT method can reach 5pC or higher.
Detection Frequency Band: Determines the system's anti-interference capability and signal feature extraction ability; e.g., UHF commonly uses 300-1500MHz, HFCT commonly uses 100kHz-100MHz.
Localization Accuracy: Especially important for long-distance equipment like cables; dual-end localization accuracy can reach within ±3 meters.
Anti-Interference Capability: Whether the system incorporates anti-interference designs such as hardware shielding, software filtering, and multi-signal cross-validation, directly affecting alarm accuracy.
Installation Method: Whether it supports installation without power outage, and whether sensors are compact and safe without affecting normal equipment operation.
Market and Manufacturer Overview
Currently, online partial discharge monitoring products on the market are mainly provided by manufacturers with system integration and algorithm capabilities, rather than pure sensor manufacturers.
Domestic Manufacturers: Such as Kanggaote (offering multifunctional integrated devices like "Nezha" and "Zilong"), Huafu Chuangjian, Hangzhou Xihu Electronics Research Institute, Jiangsu Jiuchuang Electric, Shaanxi Public Intelligence, etc., with product lines covering GIS, switchgear, cables, and other scenarios, emphasizing multi-mode fusion, edge computing, and domestic adaptation.
International Manufacturers: Such as Power Diagnostix (ICMmonitor series), whose products are characterized by high integration, powerful expert analysis software, and compliance with international standards, suitable for permanent online monitoring of transformers, cables, motors, and other assets.
When selecting, it is recommended to comprehensively evaluate the manufacturer's technical solutions, product performance, and engineering implementation experience based on factors such as the type of equipment to be monitored, on-site electromagnetic environment, budget, and whether integration with existing intelligent operation and maintenance platforms is needed.
