Digital relaying scheme for EHV transmission system incorporating regulated power index (RPI) concept using synchronized measurement

Piyush M Khadke


In this research work, a new per phase protection scheme of uncompensated and series compensated transmission line is proposed using both end synchronized measurement Regulated Power Index (RPI). RPI per phase is defined as the ratio of the sum of sending end apparent power and receiving end apparent power to the receiving end power for that phase. Real part of RPI concept is used in this analysis. This scheme has immunity to series compensation current, line charging current and other end in-feed current effect. Proposed scheme uses only one cycle moving window, sample by sample checking information and has low computational burden, fast decision with high rate of accuracy even in presence of high fault resistances. The simulation results are tabulated for abundant test cases considering severe fault conditions with very low resistance, load encroaching high fault resistance conditions, internal and external faults with Fixed Series Capacitors (FSC) at various prime locations. MATLAB/SIMULINK model generated data using an actual installed 400 kV- 400 km real transmission system parameters have been used to investigate the accuracy level of the scheme. The performance results demonstrated here validate the superiority of RPI based scheme over conventional protection schemes. Extensive simulation experiments deliver accurate results which demonstrate high accuracy, simplicity and robustness of the proposed scheme.


Fault detection; power system faults; power system protection; transmission lines

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