Transformer: Detect inter-turn insulation of windings, oil-paper insulation defects, and floating potential discharges. GIS/GIL: Detect free metal particles, tip discharges, and surface contamination or cracks on insulators. Power cables: Detect insulation aging or installation process defects (such as improper peeling of semi-conductive layers) in cable bodies, intermediate joints, and terminations. High-voltage switchgear: Live detection of discharges caused by aging of internal insulation components or poor contact. Instrument transformers, bushings, capacitors: Factory type tests and preventive tests. 3. Mainstream technical features and standards for 2025-2026: With the tightening of standards such as GB/T 7354-202X (new revision in progress), DL/T 417-2025 (Guidelines for On-site Partial Discharge Measurement of Power Equipment), and the development of smart grids, current PD detectors show the following trends:
- Wiring and calibration: Select sensors (such as coupling capacitors, HFCT clamps, ultrasonic probes) based on the type of test object, and perform system calibration (injecting known charge quantities).
- Background noise measurement: Measure environmental background noise under no-voltage or no-load conditions, and set suppression thresholds.
- Voltage withstand test: Gradually increase voltage according to standard regulations (e.g., pre-applied voltage -> measurement voltage -> voltage reduction), recording the discharge quantity (pC), discharge count, and inception/extinction voltage at each voltage level.
- Pattern analysis: Observe PRPD pattern characteristics to determine the discharge type and severity.
- Location and troubleshooting: If abnormalities are found, use multi-sensor joint positioning to locate the fault point.
- Report generation: Automatically generate standardized reports containing raw data, patterns, and diagnostic conclusions.
5. Selection recommendations
- Manufacturers/Laboratories (type tests): Must select a pulse current method PD detector that complies with GB/T 7354 / IEC 60270, requiring high accuracy (0.1pC resolution) and authoritative calibration sources.
- Substations/On-site maintenance (live detection): Prefer multifunctional portable PD detectors that integrate TEV + Ultrasonic + UHF functions, with strong anti-interference capabilities, suitable for inspection of switchgear, GIS, and transformers.
- Special cable testing: Choose a dedicated cable PD testing system, equipped with high-frequency current transformers (HFCT) and capacitive couplers, supporting oscillating wave (OWTS) testing technology (if conditions permit).
- Online monitoring systems: Select fixed online monitoring devices that support IoT transmission and have edge computing capabilities (preliminary front-end diagnosis).
6. Precautions
- Safety first: High-voltage testing must strictly comply with safety regulations, maintain safe distances, and ensure reliable grounding.
- Interference elimination: On-site radio, mobile phone signals, and motor operation can cause interference; proficiency in filtering and discrimination techniques is required.
- Comprehensive judgment: Do not judge solely based on the magnitude of discharge; combine discharge pattern characteristics, development trends, and historical equipment condition for comprehensive assessment.
