Impact of Fault Resistance on Distance Relaying of Ahoada-Yenagoa Transmission Line Using Neplan

Relay protection schemes play a vital part in guaranteeing reliability and integrity of electrical power networks by promptly detecting and isolating faults in the transmission network. Fault resistance encountered during a fault event, is a crucial parameter that significantly influences the effectiveness of relay protection systems. This paper investigates the performance of a distance relying system under different fault resistance using NEPLAN software environment on a 46-km Ahoada to Yenagoa transmission line. The performance of the distance protection relaying system under single line to ground (SLG) at 80% of the transmission line with fault resistances of 0.65Ω and 2.9Ω was modeled and analyzed using NEPLAN. From our investigation, the result reveal that when a fault resistance of 0.65 Ω and 2.9 Ω was introduced in the system during a SLG at 80% of the line (zone 1), the apparent impedance seen by the relay increased from 5.475 Ω without fault resistance to 5.602Ω and 6.407 Ω respectively. The results show that for a fault resistance of 0.65 Ω, the apparent impedances (ZAPP) trajectory falls inside the impedance characteristic of zone 2 instead of zone 1 while a fault resistance of 2.9 Ω fall outside zone 2. The findings highlight the significance of fault resistance in transmission line relaying for distance protection.