Multi-zone differential protection applied to offshore wind networks

This paper starts with a review of requirements and best practices for protecting offshore wind farm collector networks. It then describes a system for current differential protection of the array cables that is based on passive sensing. The system avoids installing electronic devices at the wind turbine generator locations and instead uses classical current transformers interrogated remotely by using optical fibre and passive interface devices. The paper describes two versions of the differential protection scheme and compares it with the conventional overcurrent and distance protection as well as with the hypothetical brute-force bus differential or process bus-based protection. The key advantages of the proposed system are improving speed and sensitivity of protection, making the protection less dependent on fault current contributions, and allowing fast reconfiguration to minimise loss of generation.