Interruption reduction in secondary substations using battery energy storage systems

Reliable electric power supply is extremely important in modern societies. Distribution system operators (DSOs) are obligated to ensure high supply security, especially in deregulated electricity markets. DSO face penalties or pay compensatory costs when they are unable to supply electricity reliably to customers. DSOs can increase their supply reliability by either employing expensive high-reliability technology or backup power supply such as battery energy storage systems (BESSs) or generators. We have presented a novel mixed integer linear programming model to determine the economic feasibility of installing BESSs at a secondary substation in a medium voltage network. We have also determined the minimum capacity and optimal schedule of the installed BESS. Moreover, we have examined the cost-effectiveness of using BESSs if they are also used for peak shaving instead of remaining idle when there are no outages. We validated our simple but effective methodology by applying it to a substation network in Finland. All the interruptions were reduced with a BESS capacity of 112 kWh, and the savings were significant for BESS costs less than 300 €/kWh. Moreover, peak shaving increased the cost savings. However, the current costs of lithium-ion-based BESSs are nearly thrice as high, and they must decrease further before BESSs can be cost-effectively used for interruption management and peak shaving.