HVDC Return Conductor Fault Location Using Current Unbalance

The system dynamically switches between normal balanced operating mode and fault detection mode with unbalanced current flow. The converter firing controller can alter the firing control sequence temporarily to introduce controlled unbalance only when fault detection is required, rather than maintaining permanent complexity. This dynamic switching resolves the contradiction by making the system simple during normal operation and complex only when needed for detection.

The fault detection mechanism uses periodic injection of unbalanced current signals through modified converter firing pulses. Instead of continuous complexity, the system periodically introduces detection signals at specific intervals or triggered by protection relays, allowing fault detection capability while maintaining simple operation during non-detection periods. This periodic action reduces overall system complexity while preserving detection reliability.

The converter firing controller, which already exists for normal HVDC operation, is made multi-functional by adding fault detection capabilities. The same controller that manages power transmission also introduces detection signals and processes measurement data for fault location. This eliminates the need for separate dedicated detection devices, achieving precise fault measurement without increasing device complexity or cost.

The existing measurement infrastructure (current sensors, protection relays) is utilized for fault detection purposes. The system serves itself by using its own operational components for both power transmission and fault detection functions. The converter firing controller self-modifies its operation to inject detection signals, and existing measurement devices automatically capture the resulting current changes, eliminating need for additional specialized equipment.