The lightning impulse test is a crucial high-voltage test for evaluating the insulation strength of electrical equipment, used to simulate the equipment’s tolerance to lightning overvoltage during operation.
I. Main Components of the System
A complete lightning impulse voltage test system consists of multiple core components that work together. The functions and composition of each part are as follows:
Impulse Voltage Generator
As the core of the system, its function is to generate impulse voltage waveforms that meet the standard requirements. This device is built based on the Marx circuit principle and consists of multiple levels of energy storage capacitors, charging resistors, front-end resistors, tail-end resistors, ignition spherical gaps, etc. By paralleling charging of each level of capacitors and then series-discharging them, extremely high impulse voltage output can be obtained.
DC Charging Device
This provides adjustable and stable DC high-voltage power for the capacitors of the impulse voltage generator. It typically includes a voltage regulator, high-voltage transformer, high-voltage rectifier diode, and filtering components. The charging voltage accuracy and stability of this device directly affect the peak accuracy of the final impulse voltage.
Measurement and Truncation System
Responsible for more accurate measurement and recording of the impulse voltage, it mainly includes the following components:
Reducer: Reduces the high voltage proportionally to a safe low voltage that the measuring instrument can handle. The damping capacitor reducer, due to its excellent performance, has become the mainstream choice.
Digital Recorder: Uses a high-speed, high-resolution digital oscilloscope to collect, display, and analyze the low-voltage signals transmitted by the reducer, calculating key parameters such as peak value, front-end time, and half-peak time.
Truncation Gap: Used to truncate the impulse wave at the specified time (such as 2-6 microseconds), generating a “lightning impulse truncheon wave” to simulate the breakdown of insulators under impulse conditions.
Automatic Control System
As the command center of modern test systems, it is usually composed of industrial computers, dedicated control software, and programmable controllers. This system realizes the automatic control of the entire test process, covering voltage setting for charging, automatic ignition, waveform parameter calculation, test sequence management, data storage, and report generation, and integrates safety interlock functions.
Test Sample and Auxiliary Facilities
Test Equipment: It is part of the system circuit, and its equivalent capacitance is a key factor affecting the waveform and generator selection.
Grounding System: Requires low-impedance, large-area good grounding conditions to ensure a smooth discharge circuit and personnel safety.
Shielding Test Hall: Used to prevent intense electromagnetic radiation from high-voltage discharge, avoiding interference to the measurement system and surrounding electronic equipment.
II. Key Points and Steps for Equipment Selection
The core goal of selection is to ensure that the equipment can generate waveforms that meet the standards for a specific test sample. The selection process should follow the following logical steps:
Step 1: Clarify Test Requirements
Determine the higher test voltage: Review the national or international standards followed by the tested product to determine the required peak values of full-wave and truncheon test voltages.
Evaluate Larger Load Capacitance: Determine the category of capacitors with larger capacitance in the tested product and estimate or measure its equivalent ground capacitance. This parameter is the most critical technical indicator in the selection process.
Step 2: Calculate Key Parameters of the Impulse Voltage Generator
Nominal Voltage: The higher output no-load voltage of the generator, which should be 10%-20% higher than the required higher test voltage, to compensate for the load drop and reserve margin for adjustment.
Nominal Energy: As the core indicator determining the generator’s ability to drive large-capacity load, the energy storage of the generator must be sufficient to generate the standard 1.2/50 microsecond waveform when connected to a large-capacity test sample. Usually, detailed calculations based on the test sample capacitance and output voltage are required using the efficiency formula to ensure that the load capacitance is within the effective load capacity range of the generator.
Waveform Adjustment Capability: The front-end resistors and tail-end resistors of the generator must have sufficient adjustable range to adapt to different capacitance test samples and achieve precise output of standard waveforms. Step 3: Select the appropriate measurement and control system
Measurement system: Choose a combination of a damping capacitor divider with sufficient bandwidth (usually greater than 20 MHz) and a high sampling rate digital recorder. The entire measurement system must be regularly calibrated to ensure that the measurement uncertainty meets the requirements.
Control system: Prioritize systems with high automation and mature software functions to improve test efficiency, test repeatability, and operational safety.
Selection summary: For test samples with small capacitance, the selection focuses on voltage level and measurement accuracy; for test samples with large capacitance, the generator energy is the primary determining factor for selection, and a rigorous load capacity calculation must be conducted.
Post time: Jan-15-2026