Although this type of discharge does not immediately cause equipment short circuits, its long-term presence can gradually corrode the insulation layer like "termites boring into wood," eventually leading to major failures. Therefore, this instrument is a core tool for preventive testing and condition-based maintenance in power systems.
Combining the latest technological developments (as of 2026), I will provide you with a detailed interpretation of the core principles, mainstream technologies, and purchasing considerations for this instrument:
1. Core Principle: How Does It "Hear" Discharges?
When partial discharge occurs, it generates various physical and chemical phenomena. The tester captures these signals to assess the health of the equipment. Currently, the mainstream detection technologies mainly include the following four types:
Table
Detection Technology Abbreviation Principle and Features Applicable Scenarios
Pulse Current Method ERA/IEC 60270 The most classic and authoritative. It captures the pulse current generated by discharge through detection impedance, allowing precise quantification (measuring in pC). It is the standard method for factory and type tests. Offline quantitative testing of transformers, cables, and instrument transformers.
Ultra-High Frequency Method UHF Strong anti-interference. It receives electromagnetic waves from 300MHz to 3GHz radiated by discharges. It has extremely high sensitivity and can avoid most low-frequency interference in the field. Online monitoring of GIS (Gas-Insulated Switchgear) and transformers.
Ultrasonic Method AE Precise positioning. It captures mechanical vibration sound waves generated by discharges. Using the "time-of-flight method" (time difference between multiple sensors), it can precisely locate the discharge source. Fault location in transformers, GIS, and high-voltage cables.
Transient Earth Voltage Method TEV Non-contact and convenient. It detects electromagnetic pulse voltages induced on the surface of metal enclosures due to internal discharges. No power outage is required; testing is done directly on the enclosure surface. Live-line inspection of switchgear and ring main units.
2. Instrument Types and Functional Classification
With technological development, current partial discharge testers are mainly divided into two categories:
Portable Inspection Instruments (Handheld)
Features: Small size, light weight (typically <5kg), built-in battery, operated like a tablet.
Functions: Integrated with multiple sensor interfaces such as TEV, ultrasonic, and earth electrical wave. Mainly used for daily inspections of substations and distribution rooms to quickly identify hidden dangers.
Intelligence: Modern instruments are equipped with AI algorithms that can automatically identify interference signals and generate PRPD (Phase-Resolved Partial Discharge) patterns to assist in judging discharge types (such as corona, floating discharge, and air gap discharge).
Online Monitoring Systems (Fixed)
Features: Long-term installation on critical equipment with real-time data upload.
Functions: 24/7 continuous monitoring, combined with edge computing technology, immediately alarms when abnormal trends are detected, achieving a transition from "periodic maintenance" to "condition-based maintenance."
3. New Technology Trends in 2026
According to the latest industry developments, partial discharge testing technology is evolving in the following directions:
Multi-parameter Fusion: No longer a single method, but a fusion analysis of electromagnetic (UHF), acoustic (AE), and optical signals, greatly improving diagnostic accuracy.
Standard Updates: The traditional IEC 60270 standard was renamed to "Charge-based Partial Discharge Measurement" in 2025, and the new GB/T 42287-2022 standard also places greater emphasis on the standardization of electromagnetic and acoustic methods.
High Frequency and Digitalization: Sampling rates are increasing (e.g., above 200MS/s), enabling the capture of nanosecond-level weak signals; instruments are commonly equipped with touchscreens and wireless transmission functions, supporting remote expert diagnosis.
4. Purchasing and Usage Recommendations
If you need to purchase or use such instruments, it is recommended to focus on the following core indicators:
The detection target determines the technical route:
Testing switchgear: Prefer instruments with TEV + ultrasonic functions.
Testing GIS: Must choose instruments with UHF (ultra-high frequency) + ultrasonic functions.
Testing cables/transformers for factory use: Need pulse current method instruments that comply with the IEC 60270 standard.
Anti-interference capability: The field electromagnetic environment is complex, so the instrument must have anti-interference functions such as digital filtering and time-domain windowing; otherwise, all you measure is noise.
Sensitivity: Detection sensitivity should be at least at the 0.5pC (picocoulomb) level to discover early minor insulation defects.
Data analysis software: Hardware is just the foundation; powerful host computer software (capable of automatically generating reports and performing pattern analysis) can greatly improve work efficiency.
In summary, the partial discharge tester is a "mine detector" for ensuring the safety of the power grid. For maintenance personnel, mastering PRPD pattern analysis and multi-sensor joint positioning is key to maximizing the value of this instrument.
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