Mathematical Modeling of Electrical Grid Current and Voltage Waveforms for Protective Relay Tests Under Actual Faulty Grid Conditions

摘要

Protective relays need to be tested under actual faulty grid conditions. On the other hand, their subsystems, as the signal conditioners, A/D converters, synchronization devices and digital filters, often need to be tested with current and voltage waveforms containing known DC, fundamental and harmonic components, since the relay operation principles are usually based on these components. Available on the market, there are many EMTP to generate high-fidelity faulty waveforms and many test sets to playback COMTRADE files capable of supporting most test cases for relays. However, these devices do not have the ability to formulate a physically meaningful grid current and voltage mathematical model. That model can be useful to improve protective relays performance tests by comparing the relay operation with its mathematical model. Besides, the waveforms model grants flexibility and accuracy to resample an actual fault register. Further, the model can be useful in relay coordination studies, performed with EMTP. In this work, we propose a fitting scheme to build a physically meaningful current and voltage waveforms model from EMTP or actual grid fault registers. Five hundred fifty current or voltage waveforms were fitted by our scheme and suitable models were achieved, based on the coefficients of determination, which is the selected measure of goodness of fit...