Power System Protection Coordination Review for the Shiroro Hydropower Station Transmission Network, Niger State

This study conducts a protection coordination review for the transmission network associated with the Shiroro Hydropower Station in Niger State, North Central Nigeria, with the objective of verifying selectivity, sensitivity, and speed of the existing protection schemes and identifying any coordination gaps requiring remedial action. Shiroro Hydropower Station generates 600MW and feeds the national grid through 330kV transmission lines, making its protection system reliability critical to the stability of Nigeria's interconnected electricity network. The study uses the ETAP power systems analysis software platform to model the Shiroro station's generator protection scheme, unit transformer differential protection, 330kV busbar protection, and associated line protection relays. Network parameters including generator impedances, transformer characteristics, and line parameters were obtained from TCN engineering records. Short circuit analysis was performed for three-phase, single-line-to-ground, line-to-line, and double-line-to-ground faults at all significant network nodes. Relay settings were extracted from current relay setting records and entered into the ETAP protection coordination study. Results identify two coordination overlap zones where adjacent overcurrent relays do not maintain adequate grading margin, potentially causing simultaneous tripping of multiple circuits for faults in a shared zone. Generator out-of-step protection settings are identified as potentially not aligned with the current stability characteristics of the network post recent generation additions. Recommendations include revised relay settings for the two identified coordination deficiencies and a stability study to inform updated out-of-step protection parameters. Keywords: protection coordination, hydropower, Shiroro, transmission network, Niger State.