A commercial relay model for the RTDS validated against the actual relay

This paper presents a relay model based on a manufactured differential transformer relay, SEL-787, developed in a real-time digital simulator. The objective of this study was to develop the model and to compare its performance to the actual relay and to a generic built-in model. With the proposed model, it is possible to implement studies in real-time simulators not only with the physical relay under analysis, but also with the surrounding protection system. The use of many relays for a real-time simulation test can be very expensive and complex. This paper presents the possibility of using models, based on actual relays, in the surrounding areas to cover all possible protection problems. The proposed model presents a new modeling technique and the comparisons to the relay itself and to the built-in generic model were made not only in terms of algorithms but also in terms of response time. The model’s performance was studied for different situations that interfere with the relay daily operation and it presented good adherence to the actual relay. This could not be observed in the built-in real-time simulator model.