Research on protection intertripping schemes for metro DC power systems based on goose network

In conventional designs of metro DC power supply systems, signal transmission for intertripping functions, including bilateral intertrips of contact line protection, circuit breaker failure protection intertrips, and frame leakage protection intertrips, relies on control cables. This not only results in a multitude of circuits, high I/O demands, substantial cable usage, and intricate wiring topologies, but also lacks compatibility among protective relay devices from different manufacturers. This issue has become a key industry concern. Although some solutions have been put forth in previous research, they still have shortcomings. This paper comprehensively evaluates the pros and cons of the existing approaches and proposes a networked protection scheme based on GOOSE communication technology, which completely replaces control cables between protective relay devices, thereby ensuring reliable transmission of various intertripping signals. In the context of contact line protection, protective relay devices monitor the status of the bypass isolator to determine intertripped targets and directly issue trip commands, enabling efficient intertrips without the need for signal relay under the over-zone bilateral feeding operation condition. For breaker failure protection, two distinct intertripping schemes have been adopted and implemented on respectively on the protective relay devices associated with the incomer, regenerative braking, and feeder breakers. In frame leakage protection, four independent intertripping logics, designed to address current and voltage leaks in various DC cabinet frames, are implemented on negative pole protective relay devices, thereby ensuring precise control over the scope of intertrips. Finally, the real-time performance of signal transmission is theoretically analysed and validated, with comparisons made against other existing schemes. Through practical testing and analytical evaluation, the proposed scheme achieves networked DC protection for metros, characterised by a simplified and clear network structure, easy compatibility and expandability, comprehensive intertripping functions, and high real-time performance.