The development of the unidirectional blocking based pilot protection for the T-connection lines

Due to the limited land resource, T-connection lines whose rated voltage are not larger than 110kV are more and more popular in the distribution network. However, it is found that the quickness and selectivity of the conventional relay protection cannot be both satisfied when it is employed in the T-connection lines. Based on the detailed analysis on the existing protection configuration, the optimized protection configuration scheme of the T-connection lines is proposed, which includes the unidirectional blocking based pilot protection principle and the inter-substation communication solution. Subsequently, the novel protection device is developed, and the functions and performance are tested with the closed loop test system built in the environment of RTDS. The test results validate the excellent performance and reliability of the novel protection device.