Dow Terneuzen, the second-largest site of Dow Chemical, relies on the ELSTA cogeneration plant to supply electricity and steam to its production facilities while contributing to the Dutch national grid. Ensuring stable operation is critical for safety and reliability. While internal disturbances are managed by existing protections, external grid faults pose challenges for detection and for enabling a controlled transition to islanded operation.
This thesis develops and validates an islanding tripping scheme for Dow Terneuzen. The objectives are to design a protection logic based on frequency and undervoltage detection, establish a load shedding strategy to maintain generator stability during islanding and validate the protection logic using online simulations and hardware testing. A dynamic model of the power system was created in ATP-EMTP, including synchronous machines with governors and excitation systems, transformers, and dynamic loads. Fault scenarios were simulated to assess stability, determine critical clearing times, and validate the protection logic. The protection logic was then programmed into a Siemens 7UM85 relay using DIGSI5 and tested with an Omicron CMC 356+, where COMTRADE signals from simulations were replayed into the relay. Relay responses were analyzed using the Fault Record tool SIGRA and compared with the online simulation results.
The results show how generator dynamics affect stability, confirm the need for rapid load shedding, and highlight challenges in designing a reliable islanding tripping scheme. The comparison between ATP-EMTP simulations and relay tests demonstrates the effectiveness of the proposed scheme and provides practical guidance for implementing reliable islanding protection at Dow Terneuzen.