To adapt to voltage fluctuations and load changes in the power grid, transformers are usually equipped with voltage regulating devices. No-excitation voltage regulation (no-load voltage regulation) changes the number of winding turns through a tap changer in the power-off state, and the adjustment range is generally ±5% or ±2×2.5%. On-load voltage regulation (OLTC) can automatically adjust the voltage under load, with a voltage regulation range of ±8×1.25% or wider. The on-load tap-changing switch is one of the components with the highest technical content. It is composed of a selector, a toggle switch and a drive mechanism. It can complete the resistance transition switching when the current crosses zero, avoiding the generation of arcs. Advanced electronic on-load tap changers use thyristor assistance for switching, achieving arc-free operation and significantly extending the service life of the equipment. The reliability of the voltage regulating device directly affects the power supply quality, and its mechanical life is usually required to reach more than 500,000 operations.
