Quantizing branches' responsibility for voltage sags/swells and flicker events.

• Four new indices are defined to quantize branches responsibility to sag/swell and flicker. • The indices are calculated using a cumulative approach in real-time, so the decision can be made upon a long-time duration. • The indices are based on the RMS values of the voltage and current which can be communicated every cycle. • The calculation algorithms are implemented in a recursive way to minimize the computational burden. The purpose of this study is to find simple cost-efficient algorithms for real-time quantizing the responsibility for power quality issues in every branch in an industrial network. The study is focused on voltage sag/swell and flicker which are caused by the time variation characteristics of loads. Here by using the RMS values of the voltage and current, four indices are defined. Cumulative-recursive equations are used to reduce the computation load and to be able to evaluate the power quality problems in real-time. Two indices quantize the loads' responsibility in sag/swell events. The duration of the sag/swell events is considered in the second index. Two indices are proposed for flicker. The first flicker index is based on the FFT of the flicker powers in the individual flicker frequencies. The second flicker index is based on the FFT of the calculated time-varying load admittance corresponding to flicker range frequencies. The load variation coherency of the different branches affects the first flicker index while it has no impact on the second one. The performance of the proposed indices is tested using simulation data, actual records from electric arc furnace and a wind farm, and a laboratory test. Results reveal that the proposed indices efficiently quantize branches' responsibility in the sag/swell and flicker events. The sag/swell indices increase after every event caused by the responsible branch in proportion with the event depth and duration. The flicker indices increase in proportion to the flicker powers according to IEC868 flicker sensitivity coefficients. [ABSTRACT FROM AUTHOR]