What is the maximum voltage of a lightning impulse generator?

1. Conventional and Typical Range

Industrial and University Laboratories: For testing conventional high-voltage equipment (such as transformers, cables, insulators), the typical voltage rating of common lightning impulse generators usually ranges from 1000 kV to 6000 kV. This range already covers the testing needs for the vast majority of power equipment.

For example, a 2400 kV or 3600 kV generator is a standard configuration in many large high-voltage laboratories.

National or World-Class Large Laboratories: To research Ultra-High Voltage (UHV) transmission technology (voltages exceeding 800kV AC or 1100kV DC) and the insulation performance of air under extreme conditions, larger generators are built.

The voltage of these generators can reach 8000 kV or even higher.

2. World Record and Extreme Cases

The world's highest voltage lightning impulse generator currently reported is located in China.

State Grid UHV DC Test Base: The impulse voltage generator built there has a nominal voltage as high as 12,000 kV (12,000 kV or 12 MV). This represents the world's highest level and is primarily used for UHV equipment research and long air gap discharge studies.

3. Factors Determining the Maximum Voltage

The maximum output voltage of a lightning impulse generator is not arbitrary; it mainly depends on the following core factors:

Number of Stages: Impulse generators typically use a Marx circuit. It charges multiple capacitors in parallel and then discharges them in series to generate high voltage. The voltage is roughly equal to the charging voltage per stage × the number of stages. Therefore, more stages theoretically yield a higher output voltage.

Charging Voltage per Stage: This is the charging voltage that a single capacitor module can withstand.

Structure Size and Insulation: Higher voltages require higher insulation levels. The physical dimensions (height, radius) of the generator must be large enough to prevent internal flashover or discharge to the surroundings before reaching the target voltage. This is also why ultra-high voltage generators are very large.

Efficiency: Due to the presence of stray capacitance and circuit inductance, the actual output voltage will be lower than the theoretical value. A well-designed generator can have an efficiency of over 90%.

Summary