Implementation and Application of Practical Traveling-Wave-Based Directional Protection in UHV Transmission Lines

摘要

Traveling-wave-based protection is becoming attractive in ultra-high-voltage (UHV) transmission systems due to the requirement for high-speed protection. However, the poor transfer characteristics of coupling capacitor voltage transformers (CCVTs) for high-frequency voltage have strictly limited its application. A novel traveling-wave-based protection scheme considering the characteristics of CCVTs and current transformers is proposed in this paper. The dyadic wavelet transform is used to extract the polarities of voltage and current traveling waves for fault direction identification. A prototype is further developed for practical applications. Extensive laboratory tests are performed to assess the performance of the developed scheme. The prototype has been applied to the 750-kV substations in China and an external fault was recorded during the operation period, validating the effectiveness and reliability of the proposed protection principle.