Main Detection Technologies and Methods A. Electrical Method (Pulse Current Method - IEC 60270 Standard) Principle: Measure the pulse current generated at both ends of the test object through a coupling capacitor and detection impedance. Advantages: Quantitatively accurate (unit: pC), it is the benchmark method for factory and type tests. Disadvantages: Weak anti-interference capability, requiring a shielding room or complex on-site noise reduction; limited transmission distance for low-frequency signals. Applicable to: Factory tests and laboratory precision measurements of transformers, instrument transformers, and cables. B. Ultra-High Frequency Method (UHF Method) Principle: Use built-in or external antennas to receive 300MHz-3GHz electromagnetic waves generated by PD. Advantages: Extremely strong anti-interference capability (avoiding low-frequency grid noise), extremely high sensitivity, suitable for online monitoring and GIS (Gas Insulated Switchgear) detection. Disadvantages: Difficult to directly calibrate to pC values (usually expressed in dBm or relative amplitude), requiring the establishment of correlation models. Applicable to: GIS/GIL, transformers, high-voltage cable terminations. C. Acoustic Emission Method (AE Method) Principle: Use piezoelectric sensors in contact with the equipment enclosure to receive mechanical vibration waves generated by PD. Advantages: Precise positioning (via time-difference of arrival), immune to electromagnetic interference, can distinguish between internal and surface discharges. Disadvantages: Signals attenuate quickly in solids/liquids, short detection distance, requiring multi-point deployment. Applicable to: Transformer tanks, GIS enclosures, cable joint positioning. D. High-Frequency Current Transformer Method (HFCT Method) Principle: Clamp-type sensors are placed on grounding wires to sense high-frequency current signals. Advantages: Non-invasive, easy installation, no need for outage (online detection), suitable for cables and rotating machines. Applicable to: High-voltage cables, generator/motor stator windings. 3. 2026 Technology Development Trends and Characteristics Current partial discharge testers have evolved significantly compared to a few years ago: Multi-sensor Fusion: Single methods are prone to misjudgment; modern instruments integrate UHF + AE + HFCT + TEV (Transient Earth Voltage) modules simultaneously. The system automatically synthesizes multiple signal features, greatly improving defect identification accuracy (>95%). AI Intelligent Diagnosis and Pattern Recognition: Built-in deep learning algorithms automatically analyze PRPD patterns (Phase-Resolved Partial Discharge patterns). Can automatically identify typical defect types: internal void discharge, protrusion discharge, floating potential discharge, surface discharge, and provide confidence scores. Equipped with "self-learning" capability, continuously enhancing recognition ability as the database updates. Wireless Synchronization and Networked Monitoring: Abandoning cumbersome fiber optic synchronization lines, adopting high-precision GPS/Beidou timing or wireless RF synchronization technology to achieve multi-channel distributed measurement. Supports the Internet of Things (IoT), with real-time data upload to the cloud, enabling remote expert consultation and trend analysis. Portable and Handheld: Inspection instruments weigh <2kg, featuring touchscreens, long-lasting batteries, and even integrated AR (Augmented Reality) functionality, directly overlaying discharge source locations on the screen. Anti-interference Algorithm Upgrades: Advanced algorithms such as wavelet transform and neural network filtering are used to extract weak PD signals from extremely strong on-site electromagnetic noise backgrounds (signal-to-noise ratio improvement of over 20dB). 4. Main Application Scenarios Table Application Object Common Detection Methods Detection Purpose Power Transformers UHF (internal/external), AE, HFCT Detect winding insulation, oil-paper insulation voids, suspended impurities, protrusion discharge. GIS/GIL (Gas Insulated Switchgear/Line) UHF (internal sensors), AE Core application. Detect spacer cracks, metallic particles, conductor burrs, poor contact. High-Voltage Cables and Accessories HFCT, TEV, OWTS (Oscillating Wave) Detect water trees/electrical trees in cable body, defects in intermediate joint manufacturing, moisture in terminations. Rotating Machines (Generators/Motors) PDCoupler, HFCT, TEV Detect stator winding slot looseness, end-winding insulation wear, semiconductor coating detachment. Instrument Transformers (CT/PT) Pulse Current Method, UHF Detect insulation moisture, capacitive screen breakdown, internal floating discharge. Switchgear (Medium Voltage) TEV (Transient Earth Voltage), AE Rapid screening of surface discharge and floating discharge in busbars, circuit breakers, and insulators within cabinets. 5. Main Brands and Market Overview (2026 Perspective) International First-Line Brands: OMICRON (Austria): Industry benchmark, MPD series known for high precision and powerful software analysis, widely used in laboratories and high-standard field applications. Doble (USA): Dominant in the North American market, specializes in online monitoring systems. HV Diagnostics / Techimp (Italy): Leading in cable oscillating wave testing. PDD (UK): Focuses on ultrasonic and TEV technologies. Leading Domestic Brands (China): Wuhan Moen (MOEORW), Wuhan Huatian Electric Power, Shanghai Sute: Provide cost-effective portable and online monitoring equipment, with technology approaching international levels, especially rapid progress in UHF and AI diagnostics. Xi'an Gaode, Baoding Tianwei: Deep accumulation in transformer and GIS-specific detection. Products transformed from research institutes under State Grid/China Southern Power Grid: Customized for specific grid needs, with excellent compatibility.