As power systems continue to demand higher reliability in power supply, traditional preventive testing during outages can no longer fully meet the timeliness requirements for equipment condition assessment. Zinc oxide surge arresters operate continuously under service voltage; once internal varistors become damp or aged, resistive leakage current increases directly, potentially leading to thermal breakdown and even system short-circuit accidents. Therefore, using live-line surge arrester testers to conduct online monitoring without power interruption—enabling real-time tracking and trend analysis of metal oxide surge arrester operating conditions—has become a key technology for power equipment condition monitoring and fault diagnosis.
I. Working Principle and Core Measurement Parameters
Currently, most live-line surge arrester testers employ harmonic analysis (projection method) as their fundamental measurement principle, with the implementation process divided into two steps:
Signal Synchronization and Acquisition: High-precision sensors synchronously capture the total leakage current signal from the arrester’s grounding lead, while phase reference signals are obtained via secondary circuits of busbar voltage transformers or through wireless non-contact probes.
Phasor Decomposition and Calculation: Based on digital signal processing techniques, the phase difference between total current and voltage is accurately calculated. Using vector projection formulas, the total current is decomposed into two components: resistive current (in phase with voltage) and capacitive current (90 degrees out of phase).
During field testing, a set of core parameters forms the basis for evaluating the insulation performance of surge arresters. The definitions of these indicators are as follows:
Total Current (Ix): The overall leakage current flowing through the arrester. Its amplitude fluctuation serves as a macroscopic indicator for assessing the general insulation condition of the equipment.
Resistive Current (Ir): A critical parameter reflecting the aging and moisture level of the resistive varistor elements. Increases in its fundamental and third-harmonic components serve as the primary basis for judging the degradation trend of the arrester.
Capacitive Current (Ic): The current component representing the arrester’s inherent capacitance characteristics, commonly used to assist in identifying surface contamination or external environmental interference.
Phase Angle (φ): The angle between voltage and total current. Changes in this value help identify structural variations among current components.
Active Power Consumption (P): A direct indicator of internal energy loss within the arrester, highly sensitive to internal insulation defects.
II. Key Technical Features and Functional Design of Live-Line Surge Arrester Testers
To adapt to the complex electromagnetic environment of substations and ensure accurate, reliable test data, such devices have undergone specialized optimization in technical architecture and functional configuration:
(1) Diversified Voltage Reference Acquisition Methods
Wired Acquisition: Directly connects to the secondary side of voltage transformers to obtain voltage signals, minimizing phase error and suitable for routine indoor testing.
Wireless Acquisition: Utilizes non-contact electric field coupling sensors mounted on insulated rods to pick up phase signals on the high-voltage side, then transmits them wirelessly via radio frequency back to the host unit. This approach eliminates safety risks associated with long secondary wiring and significantly enhances operational safety at high-voltage sites.
(2) Multi-Level Anti-Interference Mechanisms
To address measurement errors caused by capacitive coupling between three-phase arresters, the device incorporates embedded digital filtering software with compensation algorithms. During synchronized three-phase measurements, it performs vector synthesis and compensation calculations, effectively reducing interphase electromagnetic interference and ensuring high accuracy and repeatability in resistive current decomposition.
(3) Intelligent and Lightweight Integrated Configuration
Most mainstream units feature high-capacity lithium batteries, full-screen touch color LCD displays, and the ability to store large volumes of historical test data. They support USB export for archiving and come standard with compact thermal printers capable of generating standardized test reports directly at the site.
III. Application Scenarios and Selection Guidelines
(1) Primary Application Scenarios
Periodic Live-Line Inspection: Rapid screening of the health status of operating surge arresters under normal power conditions, enabling timely identification and mitigation of major safety hazards. Fault Post-Analysis: After a surge arrester is struck by lightning or the system experiences abnormal overvoltage, immediate live testing should be conducted to determine whether internal damage has occurred.
Supporting Condition-Based Maintenance: By establishing long-term trend records of resistive current through periodic inspections, this approach supports the transition of power equipment maintenance from traditional scheduled maintenance to condition-based maintenance.
(2) Basic Principles for Equipment Selection
Determine equipment type based on application scenario: Use DC parameter testers for high-precision calibration under de-energized conditions; for online monitoring of energized equipment, AC live-line testers must be selected.
Strictly verify measurement accuracy: For AC live-line testers, focus on verifying resistive current measurement accuracy—recommended accuracy should not be lower than ±2%. For DC testers, overall combined accuracy typically requires reaching ±1%.
Evaluate adaptability to field environment:
Interference resistance: Ensure the instrument can stably eliminate inter-phase coupling interference in substations with strong electromagnetic fields.
Operational portability: Prioritize devices that are lightweight, equipped with built-in high-capacity batteries, and support wireless phase synchronization to reduce operational burden at site.
Data management capability: Pay attention to storage capacity and data transfer interfaces such as USB and Bluetooth, ensuring convenient integration of test data into backend equipment management systems.
IV. Standards and Regulations to Follow
Implementation of surge arrester live testing operations and manufacturing of testing instruments must comply with current industry and national standards. Key reference documents include:
DL/T 848.1-2004 “General Technical Requirements for Surge Arrester Leakage Current Testers”
DL/T 596 “Preventive Testing Code for Electrical Equipment”
GB/T 11032 “AC Gapless Metal Oxide Surge Arresters”
Post time: Aug-13-2026