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.

Industries such as chemical companies need a continuous power supply and the fast transfer relay Siemens 7uv68 is designed to transfer frompresent feederwhich encounters a fault to an auxiliary feeder and minimizes the transient torque of the induction motors during transfer. The relay will be installed in a DOW power plant in South Tarragona, and it should be validated that the relay can operate well in all kinds of fault scenarios and no mis-operation would occur in such power plant.
To perform the relay testing, first, the fault signals which reflect the dynamic performance of DOW Tarragona are generated by ATP-EMTP. The EMTP model of the DOWpower plant has two main parts: the Tarragona power plant and auxiliary relays (overcurrent 50/50N, differential 87T) which send tripping and blocking command to 7UV68. Besides, in order to track the frequency and phase deviation between auxiliary feeder bus and the motor bus during transfer, the frequency measurement is accomplished bya zero-crossingmethod and phase angle ismeasured byClarke transformation. The test setup is made by 2 Omicron Amplifiers and a PLC which is used to simulate breakers’ behavior formain-tie configuration.
Based on the testing requirements, the relay settings are tuned to ensure the motor bus transfer can be initiated by all kinds of faults in feeder bus, and there is no mal-operation if blocking signal is sent. The motor bus can also be transferred to the auxiliary bus when a fault occurs in transmission grid with the help of relay self-start function. Furthermore, the trip delay of differential relay 87T and the communication delay affects the transfer time and the transfer inrush behaviors.