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.