Zinc oxide arresters are key devices in power systems for protecting electrical equipment from damage caused by lightning overvoltage and operating overvoltage. Their core component is the ZnO valve plate, and during normal operation, a small leakage current composed of capacitive and resistive currents flows through the valve plate. The capacitive current is generated by the stray capacitance of the arrester and is mainly determined by the operating voltage, remaining relatively stable. The resistive current is the current flowing through the resistance of the valve plate, and its value change can directly reflect the degree of deterioration of the valve plate, such as moisture and aging.
When the valve plate deteriorates, the resistive current will increase significantly, leading to an increase in the power consumption and temperature of the arrester. In severe cases, it can cause thermal breakdown of the equipment and lead to damage. Therefore, monitoring the resistive current is an effective and direct method to determine the health status of zinc oxide arresters. The zinc oxide arrester resistive current tester is a dedicated instrument specifically designed for separating and measuring the resistive current, a key parameter, in on-site or laboratory environments.
I. Measurement Principle and Core Technology
The measurement principle of the zinc oxide arrester resistive current tester focuses on the separation of capacitive current and the extraction of resistive current. Different technical routes have different applicable scenarios and measurement performances. The mainstream and common technical types are as follows:
Harmonic analysis method: An early measurement technology, it is easily affected by grid voltage harmonics and has low measurement accuracy. It has been gradually phased out.
Compensation method (fundamental wave method): By measuring the phase of the total current and voltage, the capacitive current is calculated and compensated to obtain the resistive current. It has strong anti-interference ability and is currently the mainstream measurement technology in the industry.
Third harmonic method: Applicable to gapless zinc oxide arresters, it calculates the resistive current by measuring the third harmonic current. It is only suitable for specific types of zinc oxide arresters.
When selecting, it is recommended to prioritize instruments using the compensation method or intelligent instruments with multiple algorithm modes and automatic switching capabilities to ensure the accuracy of the measurement results and the anti-interference ability of the equipment.
II. Measurement Functions
The measurement functions of the tester directly determine the diagnostic ability for the health status of zinc oxide arresters. They need to cover basic parameters and key derived parameters, and advanced analysis functions can be selected based on diagnostic requirements. The core measurement function requirements are as follows:
Basic parameter measurement: It should have the ability to measure the total current, fundamental wave of resistive current, and capacitive current, providing basic data for the judgment of the arrester’s state.
Key derived parameter measurement: Power consumption is an important indicator reflecting the degree of deterioration of the valve plate. The instrument should have the function of measuring power consumption.
Harmonic analysis function: Advanced models can analyze the 3rd, 5th, 7th, etc. harmonic components of the resistive current, enabling more precise diagnosis of arrester fault types.
Phase angle measurement function: It can measure the angle between the current and voltage, which is the technical basis for the compensation method measurement and provides support for the accurate extraction of resistive current.
III. Signal Input Methods
The signal input of the tester is divided into voltage signals and current signals. Different input methods have different accuracies and applicable scenarios, and should be selected based on the actual on-site test conditions. The specific input requirements are as follows:
Voltage signal input
PT secondary side sampling: The standard method for voltage signal sampling, directly obtaining the synchronous voltage signal from the secondary side of the voltage transformer, with high measurement accuracy, and is the recommended method for on-site testing.
Built-in electric field induction rod sampling: Applicable to on-site testing scenarios without PT access, it is convenient to operate, but the measurement results are easily affected by the on-site electric field distribution, and the accuracy is slightly lower than that of PT secondary side sampling.
Current signal input: Obtain the current signal from the two ends of the arrester counter or the grounding lead-down line through a dedicated clamp-on current clamp. The accompanying clamp-on sensor needs to meet the requirements of high precision and high sensitivity.
IV. Technical Indicators Technical indicators are the core for evaluating the measurement performance of the tester. Special attention should be paid to measurement accuracy, measurement range and anti-interference ability. The specific requirements are as follows:
Measurement accuracy: The measurement accuracy of resistive current should usually be better than ±(5% reading + 5 digits) to ensure the accuracy of basic parameter measurement.
Measurement range: The full current measurement range should cover from tens of μA to tens of mA, and the resistive current measurement range should cover from tens of μA to several mA, to meet the current measurement requirements of zinc oxide arresters under different working conditions.
Anti-interference ability: There is strong electromagnetic interference in the power field. The instrument should have good stability and measurement repeatability to ensure reliable measurement data output in complex interference environments.
V. User-friendliness and Humanized Design
The tester should be adapted to the test environment and work requirements of the power field. The humanized design in aspects such as display operation, data management and battery life directly affects the on-site test efficiency. The core design requirements are as follows:
Display and operation: Equipped with a large-screen LCD display and a Chinese operation menu to reduce the difficulty of on-site operation and improve operation convenience.
Data storage and transmission: It should have a large-capacity data storage capability, be able to save multiple on-site test data, and support USB export or data transmission to a computer via Bluetooth, Wi-Fi, etc., for convenient data processing later.
Battery life: Equipped with a built-in lithium battery, the battery life should meet the work requirements of a full day on-site, suitable for on-site tests without external power supply.
Software support: Equipped with a corresponding upper computer software to manage test data, perform trend analysis and generate reports, improving the efficiency of data application.
VI. Standard Compliance
When selecting, it is necessary to ensure that the design, production and performance indicators of the zinc oxide arrester resistive current tester meet or exceed the requirements of relevant national, industry and international standards to ensure the compliance and authority of the instrument and measurement results.
Post time: Jan-28-2026