I. Overview
High-voltage power equipment mainly includes power transformers, gas-insulated switchgear (GIS), power cables, etc. During operation, these equipment are subjected to two types of core transient overvoltage impacts: lightning-induced lightning overvoltage caused by lightning strikes, and operational overvoltage triggered by switch operations and system faults. The impulse voltage test instrument (system) can precisely simulate these two types of transient voltage waveforms to evaluate the insulation performance of high-voltage power equipment.
Unlike the simple impulse equipment used for low-voltage electrical appliance testing, the impulse voltage test system for high-voltage power equipment is a large-scale complete test device. The equipment can achieve an output voltage of several thousand kilovolts, and its overall technical architecture is more complex. It also has strict safety design and operation control requirements, and the comprehensive technical threshold and safety standards are much higher than those of the simple low-voltage testing equipment.
II. Core Test Waveforms and Their Engineering Significance
The high-voltage impulse voltage test system needs to be capable of generating various standard test waveforms, which can fully adapt to different insulation assessment scenarios of high-voltage power equipment. The parameters, simulation conditions, and assessment focuses of various standard waveforms are as follows:
Full-wave lightning impulse: The standard typical parameters are a 1.2 μs wave front and a 50 μs half-peak value. It mainly simulates the working condition of direct lightning current injection into the equipment, and is applicable to the insulation performance assessment of all types of high-voltage power equipment such as transformers, bushings, and lightning arresters. It is the most versatile basic test waveform.
Half-wave lightning impulse: The standard wave front is 1.2 μs, and the voltage cutoff time is controlled within the range of 2 to 6 μs. It mainly simulates the actual working condition of lightning waves being interrupted and gap breakdown by the equipment. It is mainly used to assess the withstand performance of longitudinal insulation structures such as transformer windings and layers. This waveform causes a sudden voltage change and generates extremely high voltage oscillation gradients, which is the most destructive to the longitudinal insulation of transformer windings and is the key waveform for detecting insulation defects in transformers.
Operational impulse wave: The standard typical parameters are a 250 μs wave front and a 2500 μs half-peak value. It mainly simulates the routine operation conditions such as power grid circuit breaker closing, reclosing, and fault clearance. It focuses on assessing the insulation performance of transmission line insulator strings, busbar-to-ground clearances, and external insulation of equipment and cable insulation. This waveform has a long duration and high output energy, and is highly likely to cause surface flashover of equipment insulation. It is the core test basis for high-voltage external insulation assessment.
Steep wave: The wave front time is less than 0.1 μs. It mainly simulates the extremely fast transient overvoltage (VFTO) working condition of the system, and is targeted at assessing the withstand ability of precise insulation structures such as GIS insulators and the insulation of the first turn of equipment windings. It can effectively detect minor insulation defects.
III. System Composition and Technical Characteristics
The complete high-voltage impulse voltage test system is a multi-unit collaborative working complete device, not a single test equipment. Each functional unit has clear division of labor and mutual cooperation, jointly achieving the output of standard impulse voltage waveforms. The core components and technical characteristics are as follows:
Impulse voltage generator body: It is the core unit of the entire system. Based on the Marx circuit principle, it realizes high-voltage output through a working mode of parallel charging of multiple capacitors and series discharge. The upper limit of the output voltage is positively correlated with the number of stages, and the more stages, the higher the achievable test voltage.
Charging device: It mainly provides a stable and controllable DC high-voltage power supply for the capacitor group of the generator. The device integrates voltage stabilization and current stabilization functions, and is equipped with a rapid fault protection mechanism to ensure the stability and safety of the charging process, laying the foundation for precise waveform output.
Waveform adjustment component: It includes wavehead resistors, wave tail resistors, waveform adjustment capacitors, and waveform adjustment inductors, which are the key components determining the accuracy of the output waveform parameters. During the actual test process, modulation operations need to be carried out based on the capacitance parameters of different test equipment. By optimizing and adjusting the resistance-capacitance parameters, the output waveform can meet the standard tolerance requirements. The tolerance for the leading edge parameters is ±30%, and the tolerance for the half-peak parameters is ±20%.
Voltage divider and measurement system: The mainstream structure is a resistance-capacitance voltage divider, which can accurately convert the high-voltage signals generated during the test into low-voltage measurable signals. It is combined with a digital recorder and a peak voltage meter to complete the voltage data acquisition and reading. The measurement system needs to be regularly subjected to metrological calibration to strictly ensure that the overall measurement uncertainty is controlled within 3%, ensuring the accuracy and reliability of the test data.
Truncation device: This is a dedicated unit for generating lightning impulse waveforms. The common structure is a multi-stage ignition gap or a three-electrode gap. It can forcibly breakdown and discharge when the test voltage rises to the preset threshold, accurately completing the voltage truncation action, meeting the requirements of the impulse test conditions.
Computer control and measurement system: This is the core control unit of the modern high-voltage impulse test system. It integrates functions such as program-controlled charging, automatic waveform acquisition, intelligent parameter calculation, data storage, and automatic generation of test reports, significantly improving the efficiency of test operations, and enabling traceability and replay of test data.
The entire high-voltage test system adopts low-loop inductance optimization design, featuring excellent high-load adaptability. When connected to long cables, GIS busbars, and other large-capacity test samples, it can still stably output standard test waveforms. The industry’s general technical standards require that the voltage utilization coefficient of the equipment be no less than 90%.
Four. Main application scenarios
The high-voltage impulse voltage test system runs through the entire life cycle of high-voltage power equipment, covering the entire process of research and development, production, installation, and operation and maintenance. The core application scenarios are divided into four categories:
Type test: Applied in the stage of new product type determination, applying the rated impulse withstand voltage according to national and industry standards to comprehensively verify the insulation design margin of the equipment, confirming the rationality and reliability of the product design, and providing core test basis for product type determination.
Factory inspection: Applied in the production and factory inspection stage, following product standards, conducting tests on each unit or sampling tests to detect insulation defects in the production and manufacturing process, ensuring the consistency and stability of the manufacturing quality of the same batch of products.
Handover and acceptance test: Applied in the acceptance stage after the equipment is installed on site. Under the premise of having test conditions, conducting impulse voltage tests to verify that the insulation of the equipment has not been damaged during transportation, hoisting, and installation, ensuring the safe operation of the equipment.
Scientific research and development: Applied in the research and development scenarios of power equipment, used for verifying the insulation performance of new insulating materials and new equipment structures, and can also conduct scientific research tests such as simulation of overvoltage faults in the power grid and analysis of insulation failure mechanisms.
This system is compatible with a wide range of high-voltage power equipment categories, mainly including oil-immersed and dry-type power transformers, voltage and current transformers, high-voltage circuit breakers and GIS equipment, power cables and their supporting accessories, insulators, bushings, metal oxide surge arresters, and other core transmission and distribution equipment.
Five. Standard system and compliance requirements
The high-voltage power equipment impulse voltage test work must strictly comply with current national standards and special product standards. All test processes, parameter settings, and data judgments must be carried out within the framework of standards. The core general and special standards are as follows:
GB/T 16927.1 “High Voltage Test Technology – Part 1: General Definitions and Test Requirements”: This is a basic general standard for the high-voltage test field, uniformly stipulating the voltage waveforms, amplitude ranges, parameter tolerances, standardized test procedures, and on-site safety control requirements for various high-voltage tests, being the core basis for all high-voltage impulse voltage tests. GB/T 16927.2 “High Voltage Test Technology – Part 2: Measurement System”: This standard specifically regulates the calibration methods for high voltage test measurement systems, the allowable range of measurement errors, and the technical requirements for data recording equipment, ensuring the accuracy and standardization of test measurement data.
GB/T 1094.3 “Power Transformers – Part 3: Insulation Level, Insulation Test, and External Insulation Air Gap”: This is a specialized test standard for transformers, clearly defining the insulation level, impulse test voltage values, and standardized test procedures for various types of power transformers.
GB/T 7674 “Rated Voltage 72.5kV and Above Gas Insulated Metal Enclosed Switchgear”: This standard specifically regulates the insulation standards and impulse test conditions for GIS equipment, as well as the test requirements, to meet the detection needs of high-voltage gas-insulated switchgear.
GB/T 3048.13 “Electrical Performance Test Methods for Wire and Cable – Part 13: Impulse Voltage Test”: This standard unifies the impulse voltage test methods, test parameters, and judgment criteria for power cables and their accessories, providing a specific basis for insulation testing of cable-type equipment.
In actual testing scenarios, it is necessary to match corresponding specialized product standards based on the type of tested equipment, while also combining the GB/T 16927 series of general standards to determine precise test parameters, test procedures, and qualification criteria. After the test, the test report must fully retain core test data such as waveform diagrams, actual peak voltages, and atmospheric correction coefficients to ensure the validity and traceability of the test results.
Six. Engineering Selection and Operating Key Points
During the engineering selection stage of the high-voltage impulse voltage test system, a comprehensive assessment must be conducted based on test requirements, equipment compatibility, and safety regulations. The core selection indicators are as follows:
Firstly, the rated output voltage needs to be selected based on the higher voltage level of the tested equipment, with a voltage margin of 1.2 to 1.5 times reserved to ensure that the equipment can cover all types of test requirements; Secondly, the energy storage capacity, for long cables and GIS with large capacitance test samples, a system with sufficient energy storage capacity should be selected, and the required energy can be estimated by multiplying the capacitance of the test sample by the square of the voltage to ensure that the test waveform is standard without distortion; Thirdly, the automation level, for batch and regular test scenarios, an intelligent system with programmable charging, automatic wave modulation, automatic stop upon breakdown, and data communication interfaces should be prioritized to improve test efficiency; Fourthly, safety interlock configuration, the high-voltage test area must be equipped with an all-inclusive safety interlock structure including access control, discharge grounding devices, and emergency shutdown, to meet high-voltage test safety regulations.
During the test operation, it is necessary to strictly follow the standard requirements to avoid test risks and ensure data accuracy: After each change of the tested equipment, the wave modulation operation must be re-performed to confirm that the output waveform parameters meet the standards before the formal test can be conducted; After the discharge of the impulse voltage generator, the equipment must be fully static and reliably connected to the grounding rod before entering the high-voltage operation area; The entire measurement system should be sent for inspection regularly, and it is recommended to complete a professional metrological calibration once a year to ensure the continuous compliance of measurement accuracy.
Post time: Jul-01-2026