Power Engineering

Permanent URI for this collection

http://etd.aau.edu.et/handle/12345678/193

Browse

Browsing Power Engineering by Subject "and Selectivity"

Now showing 1 - 1 of 1
  • No Thumbnail Available
    Item
    Assessment and Mitigation of Relays Coordination Problems in the Protection System of Southwest Region Transmission Network of Ethiopian Electric Power System
    (Addis Ababa University, 2025-05) Solomon Sinetibeb; Fekadu Shewarega (PhD)
    The reliability and stability of transmission network basically depend on protection system coordination, especially on distance and overcurrent protection relays. In the EEP southwest region transmission network, occurrence of improper relays operation such as unwanted relay tripping outside the designated protection zone and cascading events become significant issue. This thesis tries to assess existing setting coordination for distance and overcurrent protection relays and mitigate the coordination problems. The analysis is conducted through revision of literatures, data collection, system network modeling, short-circuiting simulation, coordination evaluation, problem mitigation, and finally, concludes and provides recommendation to the authorized body. The detailed system network model is built for the regional transmission network based on collected system data such as transmission line parameters, relay types, relay settings, relay location etc. Then simulations are conducted using an integrated power system analyzing tool DIgSILENT power factory 2024 SP1 software. The simulation results have shown that the existing protection system exhibited several coordination violations and long coordination time interval (CIT), which may cause to extended fault clearance time if primary protection system fails to operate. To address these, PSO algorithm was utilized to determine optimal relays operating time setting with satisfying the coordination and relay setting limit constraints. The optimal relays setting, which obtained from PSO algorithm, were verified using simulation. The results showed that the operating time of protection relays provided a clear discrimination time of 0.2 second between backup and primary protection relays, which reduce the risk of cascading outages with fast fault clearance. These findings demonstrated that the proposed method significantly mitigate the relays coordination problems and enhance the reliability of transmission system. In addition to assessment and mitigation, this thesis offered actionable recommendation for the EEP to enhance relays selectivity across the regional transmission network.