Investigation of the Use of Rogovsky Coils for Fast Automatic Bus Transfer

Currently, devices for fast automatic bus transfer (FABT) are widely used. The reaction time of the FABT algorithm is about 4÷10 ms, as a result, the nature of the behavior of measuring elements, for example, the power direction relay (PDR) in transient state, is important for them. This work provides analytical comparison of the behavior of the amplitude and angle of the first harmonic of the output signals of current transformers (CT) with a closed core and Rogowski coils (RC) during short circuits (SC). Both primary converters in this study were assumed to be ideal (without current conversion errors). The amplitude and angle of the signals were determined using the standard discrete Fourier transform function in the MATLAB software package. A numerical estimate of the time of the transient process of the amplitude value of the first harmonic of the output signals of the primary converters was carried out for various SC parameters. It was found that in all simulated cases, the time of onset of the steady-state mode of the amplitude value of the first harmonic of the output signal of the RC is significantly less or does not differ from the similar parameter of the CT signal. In addition, the secondary signal of the RC does not have a long-term (lasting several periods of industrial frequency) oscillation, characteristic of the output signal of a CT. Based on the research carried out, a conclusion was made about the prospects of using the RC as a primary current converter for FABT devices.