High Voltage Lightning Impulse Test Systems are essential equipment for verifying the dielectric strength and insulation integrity of electrical apparatus such as power transformers, bushings, and switchgear. These systems simulate lightning strikes to ensure equipment can withstand transient overvoltages encountered in real-world operation.

Standard Impulse Waveforms and Compliance

According to international standards including IEC 60060-1 and IEEE Std 4, lightning impulse test systems must generate standardized 1.2/50 μs waveforms. The wavefront time (1.2 μs) represents the time from 30% to 90% of peak voltage, while the wavetail time (50 μs) indicates the duration from virtual origin to 50% of peak voltage on the tail. Systems must maintain waveform compliance within ±10% tolerance for both front and tail times.

Key Technical Specifications

Modern impulse generators feature voltage ratings from 100 kV to 6 MV and energy ratings from 1 kJ to 100 kJ. The Marx generator circuit configuration remains the most common design, utilizing multiple capacitor stages charged in parallel and discharged in series. Advanced systems incorporate digital control interfaces, automatic waveform recording, and real-time compliance verification.

Measurement System Requirements

Accurate impulse measurement requires calibrated resistive or capacitive dividers with bandwidth exceeding 20 MHz. Digital recording systems must sample at rates above 100 MS/s with 12-bit resolution or better. Measurement uncertainty must remain below 3% for peak voltage values and within 5% for time parameters to meet standard requirements.

Applications in Equipment Testing

Lightning impulse testing is mandatory for power transformers according to IEC 60076-3, requiring both full waves and chopped waves. The test sequence typically includes one reduced full wave, two full waves at rated voltage, and several chopped waves. Systems must demonstrate consistent performance and repeatability across all test sequences.

Performance Validation

Regular performance validation includes no-load tests to verify waveform parameters, measurement system calibration checks, and demonstration tests on reference objects. Systems must maintain overshoot below 5% and minimize oscillations on the wavefront to prevent misinterpretation of test results.

Properly specified and maintained lightning impulse test systems provide reliable verification of equipment insulation strength, contributing to the overall reliability and safety of electrical power systems worldwide.