Traveling Wave-Based Primary Protection and Fault Localization Scheme for MTDC Grid Considering IEC 61869-9 Measurement Standard

Traveling wave (TW)-based protection and fault localization requires high sampling frequency measurements (500 kHz–1 MHz) and are noncompliant to the IEC 61869–9 measurement standards, which allows maximum sampling frequency of 96 kHz for dc application. This work proposes a novel low sampling frequency (50 kHz) TW-based primary protection and real-time dc fault localization technique for multiterminal high-voltage dc (MTDC) grid which is compliant with the aforementioned measurement standard. In the proposed MTDC protection scheme, a TW arrival time (TWAT) is estimated under low sampling frequency measurement using cascaded combination of modified mathematical morphology gradient (MMG), sobel operator, and linear regression tool. Subsequently, the TWAT information at both dc link terminals is communicated via dedicated communication channel compliant to IEC-61850-9-2 standard. And if the TWAT difference between dc terminals is less than the TW propagation threshold for the protected dc line, then a dc trip signal is issued to the associated hybrid dc circuit breaker (HDCCB). For fast power system restoration, the same TWAT information is also used for real-time fault localization in the faulted dc line, which is also compliant with IEC 61869–9 measurement standards. Finally, the practical feasibility of the proposed algorithm is demonstrated through control hardware-in-loop (CHIL) testing with real-time digital simulation (RTDS) setup and TI TMS320F28379d digital signal processor (DSP) card.