Differential Power Based Selective Phase Tripping for Fault-resilient Microgrid

Modern fault-resilient microgrids(MGs)require the operation of healthy phases during unbalanced short-circuits to improve the system reliability.This study proposes a differential power based selective phase tripping scheme for MGs consisting of synchronous and inverter-interfaced distributed generators(DGs).First,the differential power is computed using the line-end superimposed voltage and current signals.Subsequently,to make the scheme threshold-free,a power coefficient index is derived and used for identifying faulted phases in an MG.The protection scheme is tested on a standard MG operating in either grid-connected or islanding mode,which is simulated using PSCAD/EMTDC.The efficacy of the scheme is also assessed on the OPAL-RT manufactured real-time digital simulation(RTDS)platform.Further,the performance of the proposed protection scheme is compared with a few existing methods.The results show that the selective tripping of faulted phases in MGs can be achieved quickly and securely using the proposed scheme.

State-of-the-art on the protection of FACTS compensated high-voltage transmission lines:a review

In recent years,the inclusion of flexible AC transmission systems(FACTS)-based compensating devices such as a thyristor-controlled series capacitor(TCSC)and a unified power flow controller(UPFC)has been increased in high-voltage power transmission systems due to numerous technical and economical benefits.However,the operation of such FACTS devices introduces harmonics and non-linearity in power system and causes fast changes in line impedance.As a result,the most widely used fixed impedance setting based distance relaying scheme finds limitation in protecting such compensated lines.Significant research has been carried out in recent years to develop new algorithms and methods to address the problem.This paper presents a comprehensive review of recent developments in the protection of TCSC/UPFC compensated high-voltage transmission lines.The relative merits and demerits of each of the available methods are also presented for comparison.Prior to detail review,the impact of TCSC/UPFC on distance protection is evaluated by using data generated through EMTDC/PSCAD on a 400 kV two-bus test power system.This study can be useful to both academic researchers and practicing engineers to gain insight on the protection of FACTS compensated transmission lines and for further development of newer algorithms.