Assessing the adequacy of the medium voltage infrastructure supplying Kampala Central Business District

Abstract

Kampala is Uganda’s major central business district and is characterized by a rapidly growing economy with increase in economic activities, industrial growth and residential power needs. This increase in load capacity over the years leads to overloading of the medium voltage infrastructure. Over loading is a disastrous effect as it leads to equipment failure such as breakdown of the medium voltage transformers and feeders which can thus result into power outages. The research was aimed at determining whether the existing medium voltage infrastructure would be able to support the increasing load demand over the load forecast period. The methodology entailed modelling the 2019 Kampala network (33kv) using Dig-silent power factory, with an assumption of lumping the 11kv loads on the low voltage side of the transformers. Bench marking was done to ensure accuracy of the modeled network. A load forecast over a period of three and five years was obtained using a 7% annual growth percentage and a load flow analysis performed on the forecasted network. With the well-set objectives and methodology, the results obtained were analyzed based on parameters such as percentage loading of transformers and feeders and voltage regulation of the bus bars to determine the critically strained network assets. For proper operation of transformers and feeders, their percentage loading should not exceed 80%. Over a five year period we observed 8 of Kampala’s substations and 5 feeders exceeding the 80% loading threshold. We also observed 3 substations whose voltage regulation exceeded the 10% threshold for proper operation. The analysis depicts that the network will be heavily loaded over the forecast period. We determined the requirements for network adequacy over the load forecast period and performed a cost benefit analysis for the requirements that had several options to determine the optimal solution.