In the verification of the insulation performance of power equipment, the lightning impulse test is an indispensable key step. Its purpose is to simulate the lightning overvoltage or operational overvoltage that the equipment may encounter during operation, in order to assess its insulation tolerance. As the core equipment for conducting this test, the selection of the impulse voltage generator should be reasonable and the application of the test standards should be accurate, which directly affects the validity of the test results and the safety and reliability of the equipment after its operation. This article systematically elaborates on the selection points and key technical standards of the lightning impulse test device based on national standards and industry practices.
Core parameters and configuration principles for equipment selection
The starting point of a reasonable selection is to clearly define the voltage level of the tested item and the requirements of the test project, and then deduce the key technical parameters of the equipment.
Nominal voltage and rated energy
These are the most basic two indicators of the equipment. The nominal voltage determines the peak value of the impulse voltage that the equipment can generate, and its selection should cover 1.2 times the test voltage of the tested item and leave an appropriate margin. The rated energy (in kilojoules, kJ) relates to whether the equipment can maintain sufficient voltage duration and waveform stability, especially for equipment with larger capacitance (such as power transformers, long cables), it has a significant impact. For example, for conventional configurations of equipment at 35kV and below, a generator of 400kV/30kJ level is usually selected, while for equipment with higher voltage levels, a device of 800kV/80kJ or higher specifications is required.
Function configuration: Selection of the clamping device
Whether to configure a clamping device is an important dividing line in the selection process. If the product standard requires a truncated lightning impulse test, a clamping gap and its triggering circuit must be configured; if only a lightning full-wave test is required, the corresponding structure can be simplified to save investment. This decision must be strictly determined based on the product standard to which the tested item belongs (such as GB 1094 for power transformers).
Control and measurement system
Modern impulse test systems generally adopt a PLC combined with a computer upper computer control scheme, and are equipped with a fiber optic transmission measurement circuit. Fiber isolation can effectively prevent high-voltage side electromagnetic interference from invading the control room equipment, ensuring operational safety and data acquisition accuracy. The accompanying digital oscilloscope or acquisition card, its bandwidth should generally not be lower than 100 MHz to meet the requirements for precise recording of standard waveforms.
Key test standards and technical points
The implementation and judgment of the impulse test must strictly follow the corresponding clauses of the current national standards and IEC standards. The core basis is GB/T 16927.1 “High Voltage Test Technology – Part 1: General Definitions and Test Requirements” (equivalent to IEC 60060-1).
Standard waveform parameter tolerance
For the standard 1.2/50μs lightning impulse full wave, the standard specifies clear allowable deviation ranges for its waveform parameters, which is the basic basis for equipment calibration and test result evaluation:
Peak value: allowable deviation ±3%
Preliminary time: allowable deviation ±30%
Half peak time: allowable deviation ±20%
Treatment of waveform overshoot
When conducting tests on ultra-high voltage equipment (usually referring to test voltages of 1800kV and above), due to the influence of circuit inductance and stray capacitance, the impulse voltage wave front and peak may be superimposed with high-frequency oscillations (i.e., overshoot). The new version of GB/T 16927.1 has made more realistic and clear regulations on this:
Limitation relaxation: The allowable overshoot limit has been adjusted from the previous strict 5% to 10%, and for test voltages above 2000kV, it can be further relaxed to 20%.
Unified calculation method: A method for determining equivalent voltage based on digital filtering technology was introduced to replace the subjective “drawing average curve” method used in the previous version. This move significantly enhanced the consistency of measurement results for waveforms with overshoot among different laboratories.
Post time: Sep-10-2026