Comparison of Main Detection Methods Table Detection Method Frequency Range Applicable Equipment Advantages Disadvantages Pulse Current Method (IEC 60270) < 1 MHz Transformers, Cables, Instrument Transformers Quantitative Accuracy (pC value calibration), International Standard Arbitration Method Poor Anti-interference, Requires Power Outage, Complex Connection Ultra-High Frequency Method (UHF) 300 MHz - 1.5 GHz GIS, Transformers, Cable Terminals Extremely Strong Anti-interference, High Sensitivity, Locatable Difficult to Quantify Absolutely (Usually Expressed in mV or dBm) Ultrasonic Method (AE) 20 kHz - 300 kHz All High-Voltage Equipment (External) Precise Location (Slow Sound Wave Propagation, Easy Distance Calculation), External Non-Contact Signal Attenuation Fast, Subject to Mechanical Vibration Interference Transient Earth Voltage Method (TEV) 3 MHz - 100 MHz Switchgear Extremely Simple Operation, No Power Outage Required, Rapid Screening Only Applicable to Metal Enclosure Surfaces, Weak Depth Detection Capability 2026 Best Practice: Typically Use "UHF + AE" Combined Location (for GIS/Transformers) or "HFCT + TEV" Combined Screening (for Cables/Switchgear). 4. Typical Application Scenarios and Processes A. GIS (Gas-Insulated Switchgear) Scenario: Once discharge occurs inside GIS, the consequences are catastrophic. Method: Use UHF internal/external sensors + ultrasonic sensors. Process: Install UHF sensors at the GIS spacer insulators. Synchronously collect signals and generate PRPD patterns. If abnormalities are found, move the ultrasonic sensor to slide on the enclosure, using the "acoustic-electric time difference" to precisely locate the discharge chamber or even specific components (such as disconnector contacts). B. Power Cables (XLPE) Scenario: Intermediate joints in long-distance cables are high-risk areas for faults. Method: High-Frequency Current Transformer (HFCT) clamped on the grounding wire, combined with Oscillating Wave Test System (OWTS). Process: Use OWTS to generate damped oscillating high voltage to stimulate potential defect discharge. HFCT captures discharge signals. Using traveling wave reflection principle, based on the time difference of signal arrival at both ends, accurately calculate the fault joint distance (accuracy ±1 meter). C. Large Transformers Scenario: Inter-turn insulation of windings, aging of oil-paper insulation. Method: Pulse Current Method (mandatory for factory/acceptance tests) + UHF Method (online monitoring). Process: Apply high voltage on the low-voltage side, detect discharge quantity (pC) through coupling capacitors, and simultaneously use UHF sensors to listen inside the oil tank to exclude external interference. 5. Key Selection Indicators (2026 Edition) Table Indicator Dimension Recommended Parameters/Requirements Description Detection Frequency Band Wideband Coverage (e.g., 10kHz - 3GHz) Supports Multiple Sensor Access, Adapts to Different Equipment Sampling Rate ≥ ≥ 1 GS/s (Preferably 5 GS/s) Captures Narrow Pulse Details, Improves Location Accuracy Dynamic Range > 80 dB Can Measure Weak Background Noise and Strong Discharge Anti-Interference Capability Equipped with Adaptive Filtering, Wavelet Denoising, AI Recognition Complex Field Environment, Anti-Interference is Core Indicator Location Function Supports Acoustic-Electric Combined Location, Traveling Wave Ranging Must Tell Users "Where the Fault Is" Pattern Analysis Built-in AI Defect Recognition Library, Supports 3D PRPD Automatically Outputs Diagnostic Reports, Reduces Manual Misjudgment Portability Host Weight < 5kg, Battery Life > 8 Hours Adapts to Field, High-Altitude, Narrow Space Operations Synchronization Method Supports Power Frequency Synchronization, GPS Synchronization, Laser Synchronization Ensures Accurate Phase Analysis 6. Mainstream Market Brands (2026 Reference) International Leaders: Omicron (Austria): Absolute industry benchmark. Its MPD 800/600 series paired with TETTEX test sources, software analysis functions (such as PhasorPlot) are extremely powerful, with the richest AI library, making it the top choice for high-end laboratories and research institutions. Doble (USA): Rich experience in online monitoring systems and aging equipment assessment. Haefely (Switzerland): Excellent in the integration of high-voltage test sources and PD detection. Domestic Mainstream: Wuhan Haomai Electric, Wuhan Huatian Electric: Domestic PD equipment has obvious advantages in cost-effectiveness and localized services. In recent years, significant progress has been made in UHF sensor sensitivity and AI algorithms, and they have been widely included in the bidding lists of State Grid and China Southern Power Grid. Shanghai Siyuan Hongrui, Baoding Tianwei Group Instrument Factory: Deep accumulation in transformer-specific PD detection and online monitoring systems. Xi'an High Voltage Research Institute transformed enterprises: Internationally advanced level in UHF detection technology for UHV GIS. 7. Operational Precautions and Safety Warnings Safety First: PD testing is usually conducted under high-voltage live or pressurized test conditions. Operators must maintain sufficient safety distance, wear full protective equipment, and strictly implement the work ticket system. Grounding is Crucial: All sensor shells, instrument shells, and non-pressurized ends of the test object must be reliably grounded at a single point. Poor grounding will introduce huge ground loop interference, leading to test failure. Background Noise Measurement: Before formal testing, background noise must be measured under no voltage condition to establish a baseline. Only signals significantly higher than background noise are considered valid PD. Phase Synchronization: PRPD patterns rely on accurate power frequency phase. Ensure the instrument's phase synchronization with the test power supply is correct (0 degrees/180 degrees aligned), otherwise the pattern will be garbled and defect types cannot be identified. Comprehensive Judgment: Do not draw conclusions based solely on one data point (such as pC value). Combine discharge pattern shape, discharge inception/extinction voltage, sound characteristics, and equipment historical operating conditions for comprehensive diagnosis. Summary Partial Discharge Testers are the "gatekeepers" of high-voltage equipment health. In 2026, choosing an excellent PD tester is not just about its sensitivity, but also its anti-interference algorithms, multi-sensor fusion capabilities, and AI intelligent diagnosis level. It can not only tell you the equipment is "sick," but also "what disease it has" and "where the disease is," thereby guiding precise maintenance strategies and avoiding blind overhauls or operation with faults. If you need to understand specific PD testing solutions for specific equipment (such as "110kV GIS" or "10kV switchgear"), or want to compare the cost-effectiveness of "offline testing" and "online monitoring," please let me know!
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