Adaptability analysis of travelling wavefront protection in LCC-UHVDC transmission lines

The existing relay protections for line-commutated converter (LCC)-ultra high voltage DC (UHVDC) transmission lines are insufficient in protection sensitivity and operation speed. The travelling wavefront fault distance information can be used to improve protection performance, which has been used in protection of voltage source converter -high voltage DC (HVDC) transmission lines. The adaptability of travelling wavefront protection in LCC-UHVDC transmission line is analyzed in this paper. First, the conditions that need to be met for the travelling wavefront protections to be able to effectively recognize faults are analyzed. Eight applicability conditions of wavefront protection are revealed from the perspective of travelling wavefront generation and practical application requirements. Then the degree of match between the applicability conditions and the conditions of LCC-UHVDC system is analyzed as a basis for assessing the adaptability of travelling wavefront protection in the LCC-UHVDC system. It is pointed out that the index coefficient-based wavefront protections are not available for LCC-UHVDC transmission lines since the hardware sampling rate of protection device is insufficient, while first peak time of transient voltage (FPTV)-based wavefront protection is available for LCC-UHVDC transmission lines if it has enough anti-noise ability. Finally, an enhanced anti-noise algorithm is proposed for the FPTV-based travelling wavefront protection. The adaptability of the travelling wavefront protection is verified by hardware-in-the-loop test and filed recording experimental data.