Ground Fault Distance Protection for Paralleled Transmission Lines

Paralleled transmission lines on the same tower can increase the power transmission capacity but bring challenges to the protection unit. The conventional distance protection schemes can easily be influenced and malfunction. This paper investigated the most commonly occurred ground fault scenarios and proposed two first zone distance protection schemes based on the measurement from only the single line of one terminal for single-phase ground faults and cross-country ground faults separately. A 500 kV and 300 mk parallel transmission testing system was built in the PSCAD/EMTDC with the parameters referring to a real operating site. The results derived from the simulation show that the proposed method can provide good fault distance estimation accuracy for different ground fault scenarios with variable fault resistance. Compared with the traditional double-circuit line protection method, the proposed method which requires the same equipment investment and offers better performance is more suitable for industry application.