Load-Flow Assessment of Federal University of Technology, Akure 11 KV Distribution Network for Solar PV Integration

Abstract

The increase in electricity demand of Nigerian universities, with an epileptic public grid, has created interest in integrating solar photovoltaic (PV) generation into distribution networks. This study presents a load-flow assessment of the 11 kV/0.415 kV distribution network of the Federal University of Technology, Akure (FUTA). Hourly load data for a month were compiled using digital smart meters for 20 distribution substations across three campus operating states, namely Academic Session, Examination Period and Academic Break, and used to derive 24-hour aggregate load profiles, substation demand factors and a system diversity factor. A single-line model of the FUTA network, comprising a 7.5 MVA grid intake transformer, a 4 MVA (2 x 2 MVA) solar PV interconnection scheme feeding an 11 kV PV Integration Bus, and a battery energy storage system (BESS), was analysed in ETAP. The assessment combines (i) a stringent PV-islanded snapshot case for the instrumented Obanla precinct segment and (ii) an extended Newton-Raphson load-flow sweep across thirteen time-segmented solar-irradiance scenarios (0-900 W/m²) combined with the three measured campus load profiles, so that PV performance is characterised across varying irradiance and demand rather than at a single operating point. The aggregate campus peak demand was 2778.1 kW at 11:00 hrs during the Academic Session (load factor 0.742), 2203.9 kW at 14:00 hrs during the Examination Period (load factor 0.680), and 1610.8 kW at 20:00 hrs during the Academic Break (load factor 0.520), with a near-unity system diversity factor of 1.000-1.013 in all states, indicating strongly coincident substation peaks. In the PV-islanded case, the two solar transformers jointly delivered approximately 485.2 kW and 423.4 kVAR to the PV Integration Bus, of which 253.8 kW reached the two instrumented busways; a power-balance calculation at the PV Integration Bus shows that ohmic (transformer and cable) losses account for less than 20 kW of the residual 231.4 kW, with the remainder attributable to reactive absorption and to power routed toward the unmonitored third busway (BusWay9) and reserve/BESS-charging capacity rather than to unexplained loss. Across the extended irradiance sweep, network voltage remained within the conventional ±10% (0.90-1.10 pu) statutory tolerance band except for a brief dip to 88.13% at SEMS Bus 2 during the low-irradiance (10%) ramp of the Academic Session, and the SEMS and CERAD distribution transformers were found to operate above rated capacity (up to 176.6% and 141.6% respectively) at every PV penetration level, confirming a pre-existing capacity constraint unrelated to the PV scheme. Active-power losses rise sharply at low irradiance, from 0.0136 MW (no PV) to 0.464 MW at 10% irradiance during the Academic Session peak window, before falling back to 0.0239 MW at 90% irradiance, underscoring the need for coordinated reactive-power management during PV ramp-up. The implications for PV hosting capacity, voltage regulation, transformer loading margins and battery dispatch strategy are discussed, and a phased, feeder-prioritised PV/BESS integration plan is recommended.