The invention discloses a high voltage to low voltage TSC device, and relates to the field of power devices. The device comprises a high voltage busbar, a circuit breaker A, a step-down transformer, an isolating switch, a current transformer, a lightning arrester, a low voltage busbar, a circuit breaker B, a thyristor switch, a series reactor, a capacitor, a microcomputer controller, a sampling PTand a sampling CT. The device combines the multiple functional features of SVC, SVG and high voltage group compensation, abandons their respective shortcomings, and is a new reactive power compensation method and idea.