Optimization of the response time of microprocessor-based protection devices in phase-sensitive railway track circuits

Аннотация

Phase sensitive track circuits are very critical in the railway automation system and rely on the quick protection of track transformers against overload and short circuit faults. The traditional electromechanical circuit breakers (AVM-1, AVM-2) have large mechanical inertia, which results in slower fault isolation. In this paper, an optimized protection device (AVM-MP) based on a microprocessor is presented that overcomes the drawbacks of traditional mechanical protection devices and the preliminary digital prototypes. The first microprocessor designs incorporated the Hall-effect sensor to suit the ACS712, but were found to have several disadvantages: 5V to 3.3V logic level incompatibility, increased noise and limited bandwidth of 80 kHz. In response, the proposed architecture has an advanced ACS724 sensor that is easily compatible with the 3.3V logic of the dual-core ESP-32 microcontroller. The optimized system, which includes a dynamic current-derivative (di/dt) fault detection algorithm, provides a bandwidth of 120 kHz and removes voltage-divider noise. Results from the experimental test and simulation using virtual show that the response time of the sensor is decreased to less than 4μs, which makes it possible to detect and isolate any transient faults early (under 1.2ms). This quick response time also helps to avoid thermal damage to the transformer windings, significantly extending the operational lifespan and safety of the railway signaling system.