An Improved Method of Traveling Wave Protection for DC Lines Based on the Compensation of Line-Mode Fault Voltage

The protection of high voltage direct current (HVDC) transmission line is the key to The protection of high voltage direct current (HVDC) transmission line is the key to development of the HVDC transmission technology. To deal with the problem that the traditional traveling wave protection (TWP) has low sensitivity under high resistance faults, an improved TWP scheme based on the compensation of the line-mode component of fault voltage (LMCFV) is proposed. The expressions of the LMCFV of HVDC system at different fault locations are derived. Conclusions can be drawn that the LMCFV and fault resistance are linear when the DC line fault occurs, whereas the linear statewill be broken for the external fault. Based on this, the LMCFV for the metal fault occurring at the DC line midpoint is used as the reference value to compensate for the faults in other cases of the HVDC systems. The protection scheme constructed based on the compensatoryLMCFVand compensation coefficient can accurately identify fault of the DC line. Finally, a +/- 800 kV model of HVDC systems is built in PSCAD to verify the protection performance. The effect of fault resistance can be eliminated by compensatory LMCFV, and the DC line fault can be quickly and reliably identified by the simulation results.