Lightning impulse voltage generators are essential test systems for evaluating the insulation performance of high-voltage electrical equipment under transient overvoltage conditions. By generating controlled high-voltage impulse waveforms, they can reproduce the electrical stress caused by lightning strikes and switching events and help determine whether an insulation system can withstand these severe transient conditions.
For manufacturers of power transformers, GIS, GIL, bushings, insulators, cables and other high-voltage equipment, impulse testing is an important part of dielectric testing and insulation design verification.
Yangzhou Sute Technology Co., Ltd. develops and manufactures high-voltage testing equipment, including conventional and SF6 gas-insulated lightning impulse voltage generators. Its lightning impulse voltage generators cover a voltage range of 20 kV to 7200 kV, with configurations designed for different test levels and applications.
What Is a Lightning Impulse Voltage Generator?
A lightning impulse voltage generator is a high-voltage test system designed to generate short-duration, high-amplitude impulse voltages with controlled waveform parameters.
Unlike a conventional AC test transformer, which generates a relatively continuous sinusoidal voltage, an impulse voltage generator produces a transient voltage pulse. This allows engineers to simulate the electrical stress that high-voltage equipment may experience during lightning strikes or other transient overvoltage events.
The generated impulse can be applied to the test object through a dedicated high-voltage test circuit and measured using a suitable high-voltage measuring system.
The general high-voltage testing framework is covered by the IEC 60060 series. The latest IEC 60060-1:2025 covers dielectric tests using direct, alternating and impulse voltages, while IEC 60060-2:2025 specifies requirements for measuring systems used for lightning and switching impulse voltages.
This distinction is important: the generator creates the required impulse, while the measuring system verifies whether the generated waveform meets the required parameters.
Why Is Impulse Voltage Testing Necessary?
Electrical insulation systems are not exposed only to normal operating voltage.
In actual power systems, equipment can experience transient overvoltages caused by:
- Lightning strikes
- Lightning-induced surges
- Switching operations
- Fault conditions
- Transient interactions between connected equipment
A high-voltage component may operate normally under its rated AC voltage but still have an insulation weakness when exposed to a very fast transient voltage.
Impulse voltage testing therefore provides a way to evaluate insulation performance under controlled laboratory conditions.
For example, power transformer impulse testing involves evaluating the insulation system against specified lightning and switching impulse stresses. IEC 60076-4 provides guidance on impulse test waveforms, test circuits, grounding practices, failure detection, measurement and interpretation for power transformers and reactors.
How Does a Lightning Impulse Voltage Generator Work?
A typical impulse voltage generator stores electrical energy in capacitors and then releases the stored energy through a controlled discharge circuit.
The basic process can be understood as:
Charging → Energy Storage → Controlled Discharge → Impulse Wave Generation → High-Voltage Measurement
1. Capacitor Charging
The generator first charges its impulse capacitors to a predetermined voltage.
For high-voltage applications, multiple capacitor stages can be connected in a suitable configuration so that a very high impulse voltage can be generated during discharge.
2. Controlled Triggering
Once the required charging voltage is reached, the triggering system initiates the discharge process.
The timing and synchronization of the discharge are important because the impulse waveform must be repeatable.
3. Impulse Formation
The stored electrical energy is rapidly released through the impulse circuit.
The circuit parameters determine the characteristics of the resulting waveform, including:
- Peak voltage
- Front time
- Time to half-value
- Oscillation and overshoot
- Energy delivered to the test object
4. Application to the Test Object
The generated impulse voltage is connected to the equipment under test through the high-voltage test circuit.
Depending on the test requirement, the test object may be a transformer, GIS, GIL, cable, insulator, bushing or other high-voltage component.
5. Measurement and Evaluation
A high-voltage measuring system records the impulse waveform and evaluates its parameters.
IEC 60060-2:2025 specifically addresses measuring systems and measurement uncertainty for high-voltage tests involving lightning and switching impulse voltages.
What Types of Impulse Tests Can Be Performed?
A modern impulse voltage generator is not limited to a single waveform.
Its lightning impulse voltage generator can be configured for:
- Full lightning impulse tests
- Switching surge tests
- Chopped-wave tests
- Shock-wave and other special waveform tests
SUTE products cover generator voltage ratings ranging from 20 kV to 7200 kV, and the generated waveforms comply with applicable GB and IEC requirements.
Lightning Impulse Voltage
Lightning impulse testing reproduces the type of transient electrical stress associated with lightning events.
For many high-voltage insulation systems, the commonly encountered standard lightning impulse waveform is represented by a 1.2/50 μs waveform, although the exact requirements depend on the applicable equipment standard and test level.
The purpose is not simply to generate the highest possible voltage. The waveform shape, peak value, timing parameters and measurement accuracy are equally important.
Switching Impulse Testing
Switching operations in high-voltage power systems can also produce significant transient overvoltages.
For ultra-high-voltage equipment, switching impulse testing becomes particularly important because the insulation coordination and transient behavior of the equipment can differ substantially from lower-voltage systems.
IEC 60060-1:2025 introduced an updated definition for standard switching impulse voltage, including a 170/2500 μs waveform definition.
This is one reason why a high-voltage impulse test system needs to provide flexible waveform adjustment rather than simply generating a fixed pulse.
Chopped-Wave Testing
In some insulation tests, the impulse waveform is intentionally interrupted or “chopped” to create a different transient stress condition.
Chopped-wave testing can be particularly useful for investigating insulation behavior under rapid changes in voltage.
SUTE's products enable the "chopped-wave test" to be performed more effectively—a capability that is crucial for research institutions and manufacturers engaged in advanced insulation research.
Major Applications of Lightning Impulse Voltage Generators
1. Power Transformer Testing
Power transformers contain complex insulation systems involving windings, insulation structures, bushings and internal connections.
Impulse testing helps evaluate whether the insulation system can withstand specified transient overvoltages.
The applicable test program can include lightning impulse and switching impulse tests depending on the transformer type, voltage class and applicable standard.
IEC 60076-4 specifically covers guidance for lightning and switching impulse testing of power transformers and reactors.
2. GIS and GIL Testing
Gas-insulated switchgear (GIS) and gas-insulated lines (GIL) are important applications for high-voltage impulse testing.
These systems use compact gas-insulated insulation structures, making their dielectric behavior under transient voltage an important part of design and verification.
SUTE's SF6 gas-insulated lightning impulse voltage generator developed for lightning impulse and switching surge testing of 1000 kV GIS or GIL.
This gas-insulated approach is particularly relevant when very high test voltages and compact test arrangements are required.
3. High-Voltage Cable Testing
Power cables and cable accessories also require impulse testing during development, qualification and research.
IEC 60230 specifies procedures for lightning impulse, switching impulse and superimposed impulse tests on cables and their accessories.
Typical test subjects can include:
- High-voltage power cables
- Cable joints
- Cable terminations
- Cable accessories
- Insulation systems
Impulse testing can help identify weaknesses that may not be revealed by conventional power-frequency withstand testing alone.
4. Insulator Testing
Insulators must maintain adequate electrical insulation under both normal operating conditions and transient overvoltage conditions.
Impulse voltage generators can therefore be used to evaluate:
- Composite insulators
- Porcelain insulators
- Suspension insulators
- High-voltage support insulators
- Other insulation structures
For research applications, the ability to adjust the waveform and test voltage can also be useful for studying insulation flashover and breakdown behavior.
5. Bushing and High-Voltage Component Testing
High-voltage bushings and other insulation components can experience severe transient electrical stress during service.
Impulse testing can be integrated into a broader dielectric test program to verify insulation coordination and product performance.
Typical test laboratories may combine impulse testing with:
- AC withstand testing
- Partial discharge testing
- DC testing
- Temperature testing
- Other dielectric tests
Why Low-Inductance Design Matters
One of the major engineering challenges in impulse voltage generation is maintaining the required waveform when the test object has significant capacitance or other electrical characteristics.
The impulse circuit therefore needs to minimize unwanted parasitic effects.
Key Features of SUTE Lightning Impulse Voltage Generators
SUTE's lightning impulse voltage generator series incorporates several features intended for high-voltage testing applications:
Wide Voltage Range
The documented voltage range is:
20 kV–7200 kV
This allows configurations to cover different test levels from relatively low-voltage laboratory applications to ultra-high-voltage testing.
Multiple Structural Configurations
including:
- HAEFELY S.E. structure
- H structure
- L structure
The appropriate structure can be selected according to the required voltage level, test object and laboratory configuration.
High Voltage Utilization
The generator is designed with a high-voltage utilization coefficient, helping make effective use of the stored energy and generator stages.
Flexible Waveform Adjustment
The system is designed to provide waveform adjustment for different test requirements, including lightning impulse, switching surge and chopped-wave testing.
Automatic Charging Control
constant-current charging and automatic control, together with high automation and anti-interference capability.
SF6 Gas-Insulated Lightning Impulse Voltage Generator
For ultra-high-voltage applications, conventional open-air impulse generators can require considerable installation space.
SUTE has also developed an SF6 gas-insulated lightning impulse voltage generator.
3000 kV gas-filled lightning impulse voltage generator, designed for lightning impulse and switching surge tests on 1000 kV GIS/GIL. The possibility of integrating this technology with an SF6 gas test transformer to create a multifunctional test platform capable of AC, impulse and, where required, DC testing.
This concept is particularly interesting for ultra-high-voltage laboratories because integrating multiple test functions into a compact gas-insulated platform can help address space and installation challenges.
Lightning Impulse Generator vs. AC Test Transformer
It is important to understand that these two types of equipment serve different purposes.
| Test Equipment | Main Function | Typical Test |
|---|---|---|
| AC Test Transformer | Generates continuous high AC voltage | AC withstand / dielectric tests |
| SF6 Gas Testing Transformer | High-voltage AC testing with compact gas insulation | GIS, cables, electrical equipment |
| Lightning Impulse Voltage Generator | Generates transient impulse voltage | Lightning impulse tests |
| Switching Impulse Generator | Generates switching surge waveform | Switching impulse tests |
| High Voltage DC Generator | Generates controlled DC voltage | DC withstand tests |
In a comprehensive high-voltage laboratory, these systems may be used individually or integrated into a broader test platform.
SUTE's product portfolio includes not only impulse voltage generators but also SF6 gas testing transformers, variable-frequency resonant systems, high-voltage DC generators, impulse current generators and automatic measurement and control systems.
What Should Be Considered When Selecting an Impulse Voltage Generator?
Selecting an impulse generator should not be based on maximum voltage alone.
Important factors include:
1. Required Test Voltage
The generator's maximum output voltage should correspond to the highest required test level, while also considering future testing requirements.
2. Test Object Capacitance
Large transformers, GIS, GIL and cables can present substantial capacitive loads.
The generator should therefore be capable of producing the required waveform under the actual test load.
3. Required Waveforms
The system may need to support:
- Lightning impulse
- Switching impulse
- Chopped wave
- Special impulse waveforms
4. Measurement System
The generator and measuring system should be considered as an integrated test system.
IEC 60060-2:2025 emphasizes the requirements for complete measuring systems and their components used to measure lightning and switching impulse voltages.
5. Laboratory Space
For high-voltage laboratories, installation height, floor area, shielding, grounding and safety distances can be major considerations.
For ultra-high-voltage applications, gas-insulated configurations may provide an alternative to conventional large air-insulated arrangements.
6. Automation and Safety
Automatic charging, triggering, grounding, interlocking, measurement and data acquisition can improve test repeatability and operational safety.
SUTE's impulse voltage and current measurement/control system supports constant-current charging based on PID control, automatic tracking, automatic grounding, preset impulse times and manual or automatic triggering.
Lightning Impulse Voltage Testing as Part of a Complete High-Voltage Test Platform
Modern high-voltage testing increasingly involves more than a single test machine.
For example, a laboratory working with GIS or ultra-high-voltage equipment may require:
AC Withstand Test + Partial Discharge Test + Lightning Impulse Test + Switching Impulse Test + DC Test + Measurement & Control
Integrating these systems can provide a more complete solution for product development, type testing, research and insulation verification.
This is also where system engineering becomes important. The generator, measuring system, test object, grounding system, shielding system and control system must work together to produce reliable and repeatable test results.
Conclusion
A lightning impulse voltage generator is a core piece of equipment for evaluating insulation performance under transient high-voltage conditions. It enables laboratories and manufacturers to reproduce lightning impulse, switching surge and other specialized impulse stresses in a controlled environment.
The performance of an impulse testing system depends not only on its maximum voltage rating, but also on waveform accuracy, load capability, circuit inductance, measurement technology, automation, grounding and overall system design.
Yangzhou Sute Technology provides lightning impulse voltage generators covering a documented range of 20 kV to 7200 kV, together with SF6 gas-insulated impulse technology for ultra-high-voltage applications. Its product portfolio also includes SF6 gas testing transformers, resonant test systems, high-voltage DC generators, impulse current generators and automatic measurement and control systems, allowing different high-voltage testing functions to be configured according to the requirements of the test laboratory.
For high-voltage equipment manufacturers, power utilities, electrical research institutes and testing laboratories, selecting the appropriate impulse voltage generator is therefore an important step toward reliable insulation testing and high-voltage equipment qualification.
FAQ: Lightning Impulse Voltage Generator
What is a lightning impulse voltage generator?
A lightning impulse voltage generator is high-voltage test equipment that produces controlled transient impulse voltages for testing the dielectric strength and insulation performance of electrical equipment.
What equipment can be tested with a lightning impulse generator?
Typical applications include power transformers, GIS, GIL, high-voltage cables, cable accessories, bushings, insulators and other high-voltage electrical equipment.
What is the difference between lightning impulse and switching impulse?
Lightning impulse testing simulates transient voltage stress associated with lightning, while switching impulse testing evaluates insulation performance under slower transient overvoltages associated with switching operations.
What voltage range can SUTE's impulse voltage generators provide?
According to SUTE's company documentation, the lightning impulse voltage generator series covers 20 kV to 7200 kV.
Does SUTE provide SF6 gas-insulated impulse generators?
Yes. SUTE's documentation describes an SF6 gas-insulated lightning impulse voltage generator developed for high-voltage GIS/GIL testing, including a documented 3000 kV gas-filled system for testing 1000 kV GIS or GIL.