Design of an Intelligent Automatic Switching Device for Protective Relay Hard Straps

This paper presents an intelligent automatic switching device for protective relay Hard Straps, utilizing a magnetic latching actuator mechanism that implements hysteresis control during operation to precisely regulate both excitation current and duration, thereby enhancing operational reliability while preventing power interruption-related failures. The system incorporates a 36-channel I/O communication module with RS-485 differential serial interface and Modbus protocol to facilitate simultaneous high-speed communication between multiple Hard Strap controllers and the host computer. Switching commands (close/open) can be initiated either locally through the integrated indicator-pushbutton switch or remotely via the host computer interface, with a dedicated status feedback circuit continuously monitoring the Hard Strap's positional state and immediately updating both the local switch indicators and remote monitoring system upon detecting any state changes, enabling fully automated local and remote control with real-time status monitoring. The device significantly enhances the intelligence level of conventional Hard Straps and provides robust support for secure and stable power system operation.