High-voltage (HV) Lightning Impulse Voltage Generator Test Systems are essential for validating the dielectric strength of power equipment, such as transformers, against transient overvoltages caused by lightning strikes or switching events. These systems simulate standard lightning impulses to ensure insulation integrity, adhering to international standards like IEC 60060-1[citation:5]. This article delves into the components, operational principles, and standards governing these test systems, highlighting their role in maintaining grid reliability.

A typical Lightning Impulse (LI) test system consists of a Marx Impulse Generator (MIG), which generates high-voltage impulses by charging multiple capacitor stages in parallel and discharging them in series. The output waveform must meet specific parameters: a rise time (T1) of 1.2 μs ±30% and a tail time (T2) of 50 μs ±20%[citation:4]. Adjusting front (R1) and tail (R2) resistors controls these times, while circuit inductance—from generators, leads, and stray elements—can cause overshoot or oscillations if not properly managed. Overshoot, a damped oscillation at the voltage peak, must not exceed 10% per IEC standards to prevent insulation damage[citation:1][citation:4].

Testing involves both Full Wave (FW) and Chopped Wave (CW) impulses. CW tests, where voltage is abruptly chopped after peaking, evaluate insulation stress under rapid transients. According to IEC 60,076, the chopped peak must exceed the FW peak, with a chopping delay of 3–6 milliseconds. Additionally, post-chopping voltage must reach zero quickly, limiting opposite-polarity overswing to under 30%[citation:1]. Precise modeling of test circuits, including transformer high-frequency behavior, is crucial to avoid non-standard waveforms that could lead to insulation failure[citation:1].

For measurements, instruments like digital recorders must comply with standards such as GB/T 16896.1-2024 (equivalent to IEC 60060-1), which specifies accuracy and calibration for impulse tests[citation:2][citation:10]. Recent updates to IEC 60060-1, including extended front-time tolerances for Um >800 kV and revised switching impulse definitions (e.g., 170/2500 μs), enhance testing precision for ultra-high-voltage (UHV) equipment[citation:5].

Challenges in LI testing include managing circuit inductance and load capacitance. Excessive inductance, often from long leads or generator internals, limits the achievable front times and capacitive load. Techniques like low-inductance design and computerized simulations help optimize parameters[citation:4][citation:7]. As UHV systems evolve, standards continue adapting to address testing complexities, ensuring reliable insulation coordination for power infrastructure[citation:9].