The zero partial discharge withstand voltage test device is a core testing instrument in the field of insulation performance evaluation for high-voltage electrical equipment. Its most critical technical feature is extremely low self-generated partial discharge under high-voltage output conditions, typically controllable within 5 picocoulombs (pC). This characteristic effectively eliminates background interference from the testing system, ensuring that the detected partial discharge signals accurately and truthfully reflect the actual insulation condition of the equipment under test, thereby providing reliable basis for insulation performance assessment.
As power systems continue to upgrade their voltage levels and operational reliability and stability requirements become increasingly stringent, the application value of zero partial discharge withstand voltage test devices has become more prominent. These devices are widely used in key stages such as quality control during manufacturing, on-site commissioning acceptance, and routine preventive maintenance of power equipment, making them indispensable core equipment for safe operation and maintenance of high-voltage electrical systems.
I. Technical Principles and Equipment Classification
Based on different technological approaches, mainstream zero partial discharge withstand voltage test devices can currently be categorized into three types. Each type differs in structural principles, performance characteristics, and applicable scenarios, enabling adaptation to diverse inspection needs for various high-voltage electrical equipment.
(1) Variable Frequency Series Resonance Type Device
The core operating principle of variable frequency series resonance devices is frequency-adjusted resonance technology. By precisely adjusting the output frequency of the power source, the inductance of the reactor forms a stable resonant circuit with the equivalent capacitance of the equipment under test. In resonance, the entire circuit exhibits purely resistive characteristics, requiring only minimal active power from the source to compensate for circuit losses, while reactive power circulates back and forth between the reactor and the test object. This enables a small-capacity power source to generate high test voltages.
These devices feature compact structure, small size, light weight, and low demand for on-site power supply capacity, offering excellent adaptability. The output voltage is a standard sine wave with waveform distortion controlled below 3%, and they exhibit superior quality factor, significantly reducing energy consumption during testing. They are primarily used for on-site commissioning tests of power cables, gas-insulated switchgear (GIS), generators, and large transformers.
(2) Gas-Insulated Zero Partial Discharge Test Transformer
Gas-insulated zero partial discharge test transformers abandon traditional oil-paper insulation structures and instead use sulfur hexafluoride (SF₆) gas as the primary insulating medium. SF₆ gas offers excellent insulation and arc-quenching properties, and the medium itself does not create conditions conducive to partial discharges, fundamentally eliminating insulation-related partial discharge interference from the device’s own structure.
This type of device achieves industry-leading partial discharge performance, with typical background discharge levels controllable below 3 pC, and high-precision models capable of maintaining stable values between 1 and 3 pC. Compared to conventional equipment, it completely eliminates environmental hazards associated with oil leakage and demonstrates stronger adaptability to complex on-site conditions such as extreme temperatures and high humidity. It is primarily suitable for factory quality inspections of high-voltage GIS equipment and gas-insulated transmission lines (GIL), and also meets the withstand voltage testing requirements for power transformers and insulating bushings at 110 kV and above.
(3) Zero Partial Discharge Induction Withstand Voltage Device
Zero partial discharge induction withstand voltage devices utilize an excitation transformer to drive a series resonance circuit and are specifically developed for electromagnetic-type voltage equipment. These devices can output high-voltage test voltages at twice the rated frequency, effectively avoiding core saturation issues during testing, thus ensuring accuracy in both withstand voltage and partial discharge measurements from a technical standpoint.
The primary function of this equipment is to test and verify the electrical withstand strength of longitudinal insulation in transformer windings. It is mainly suited for induction withstand voltage tests and partial discharge measurements on power transformers and voltage transformers ranging from 110 kV to 500 kV.
II. Key Technical Parameters During equipment selection and practical operation, it is essential to carefully verify key technical parameters, as these directly determine whether the equipment can meet high-voltage testing requirements across various application scenarios. The core parameters are as follows:
(1) Partial Discharge (PD) Level
Partial discharge level is the most critical performance indicator for non-partial-discharge withstand voltage test equipment. According to industry standards, the background partial discharge of the device itself should be controlled within 5 pC. For high-precision and highly demanding testing environments, equipment with a background PD level of 1–3 pC or lower should be selected. The lower the background noise of the equipment, the higher the accuracy in detecting weak insulation defects in the tested equipment, resulting in more precise test results.
(2) Output Voltage and Capacity
The rated output voltage of the device must fully cover the higher standard test voltages required by the equipment under test, while the rated capacity must satisfy the capacitive current demands generated during operation. For large-capacitance test specimens such as long-distance power cables and large-capacity transformers, the required reactive power for the test must be accurately calculated based on the equivalent capacitance of the equipment and the standard test voltage, thereby determining the appropriate capacity configuration. This prevents insufficient test capacity from compromising detection effectiveness.
(3) Frequency Adjustment Range
For variable-frequency series resonant devices, the typical frequency adjustment range is 30–300 Hz. For special test specimens with unique structures or materials, a wider frequency adjustment range is necessary to precisely match circuit resonance conditions, ensuring compliance with industry testing standards and enabling smooth test execution.
(4) Waveform Quality and Stability
The output voltage of the equipment must be a pure sine wave. Industry standards generally require waveform distortion to be kept within 3%–5%. Frequency stability should be better than or equal to 0.05%, enabling high-precision control of voltage and frequency throughout the test process, thus minimizing interference caused by waveform distortion or frequency fluctuations on test data.
III. Application Scenarios and Selection Recommendations
Performance advantages of different types of non-partial-discharge withstand voltage test equipment vary significantly, and selection should be made according to the specific test object and working environment to ensure both testing efficiency and measurement accuracy.
For on-site commissioning tests of long-distance power cables, variable-frequency series resonant devices are preferred. Cables typically have large capacitance, and this type of equipment significantly reduces the demand for on-site power supply capacity through resonance principles. Additionally, its portability and adaptability to diverse outdoor field conditions make it highly practical for on-site operations.
For factory tests and on-site withstand voltage testing of high-voltage GIS equipment, gas-insulated non-partial-discharge test transformers are suitable. These devices feature extremely low background partial discharge levels, enabling accurate detection of minor internal insulation defects and meeting stringent quality inspection and acceptance standards for high-voltage equipment.
For induction withstand voltage tests on power transformers and voltage transformers, non-partial-discharge induction withstand voltage devices should be used. Their dedicated high-frequency voltage output characteristics effectively prevent core saturation issues, allowing precise verification of the longitudinal insulation endurance and operational reliability of windings.
Post time: May-29-2026