Impact on breaker failure protection by using non-conventional transducers

This paper presents the study results on using non-conventional transducer outputs for breaker failure protection (BFP) functions. The paper starts with modelling of non-conventional transducers according to IEC 61869 standards by applying both analogue and digital integration methods. A basic description of BFP is then provided. A test model which includes both the primary power system and the BFP function is built in PSCAD which mimics the actual BFP function used in industry. The verification is carried by applying different faults which are inputs for non-conventional transducers, and the output of the transducers is connected to BFP function. In order to confirm the results, a protection relay configured with BFP function is tested in a hardware-in-loop configuration by running the recorded files from PSCAD model in real-time and feeding its output to the process bus interface of the relay. In both conditions, it is noticed that the BFP might trip incorrectly during switch off faults due to the longer decaying tail of transducer output if the model is just following the design demand on IEC 61869 standards with 1 Hz cut-off frequency limits regarding DC component suppression. Finally, the conclusions are given with suggested actions both in standard aspects and test aspects under digital substation environment.