Designing A Modern Substation To Minimise Cost And Time During Future Upgrades

Abstract

The Northern Cape Operating Unit in South Africa is experiencing load growth, due to residential developments, high electrification growth, agriculture and mining. The rural areas were previously not given sufficient attention, a result of slow developmental growth. The current 66 kV network experiences low voltages, under n-1 contingencies. The existing 66 kV network has no spare capacity to supply new customers. For additional capacity, Eskom should upgrade its distribution network from 66 kV to 132 kV. Eskom further upgrades their substations, due to equipment reaching their functional lifespans. The cost to maintain equipment regularly is high. Old apparatus interrupts security and continuity of supply to customers regularly. The challenge with substation upgrades, on existing substations, is the cost involved to upgrade the 66 kV substations to 132 kV. Before substation, upgrades may take place. New and existing consumers who require additional capacity are not connected, due to capacity constraints in existing substations. Older protection schemes do not possess any data storage facilities, to be utilised during fault investigations. Phase one protection schemes solely retain the flag of the previous incident, which is not adequate when investigating faults for extended periods. During substation upgrades, continuity of supply to existing customers is necessary to improve customer satisfaction and network performance. Electricity is generated and distributed instantaneously, by electricity utilities. There is occasionally an enormous amount of wasted capacity in electricity utilities. Illegal connections contribute to overloads and trips, as the network is carrying more users than initially designed. It is particularly critical to assess the economic practicability of BESS for diverse applications. The costs of energy storage systems, depend on the type of technology, the planned operation, and the hours of storage required. This dissertation further proposed a Battery Energy Storage System (BESS) design, which leads to a costly network upgrade deferral and increased self-consumption. BESS reduces environmental pollution (Environmentally friendly), reduces consumer electricity prices (Creating value for customers), provides reliable back up supply, improve network performance and create sufficient capacity on the medium voltage network. This dissertation compared different substation designs and the most cost-effective design, when upgrading modern substations, were preferred. The modern substation design reduced the complexity of substation upgrades, reduced substation upgrade expenses and improved network performance. Furthermore, the preferred modern substation upgrade designs had the lowest influence on network performance, during construction. The high voltage and medium voltage systems were reliable for n-1 contingencies. Finally, the same Control Plant schemes and cabling were re-used during substation upgrades. Design, apparatus and construction expenses of a standard 66/22 kV, 40 MVA substation, were approximately R 39,946,427. The decommissioning cost of an existing 66/22 kV substation was approximately R18,540,602, per substation. The decommissioning cost escalated the cost to upgrade an existing 66/22 kV substation to R 58,487,029. The minimum energy storage system cost was approximately R4,931,500 for a 1 MW power conversion system and R4,931,500, for a 1 MWh battery system. The modern substation designs, including upgrade costs, reduced capital expenditure and operational expenditure to R 43,169,816, during substation upgrades. Substation upgrade cost comparison was to calculate the most cost-effective design for substation upgrades, when upgrading high voltage networks or deferring substation upgrades.