Analysis of Distribution Transformer Overload Management Using Battery Energy Storage System

Abstract

Peak load power plants, certain types of renewable energy sources, are designed to provide electricity during periods of high demand when there is a significant increase in power consumption. These power plants typically have higher operational costs due to the need for quick start-up times and increased fuel consumption. To mitigate the reliance on expensive peak load power plants, suppliers often implement various techniques to reduce peak load and shift the demand to off-peak hours. Pumped storage hydro power plants work by using excess electricity during low demand period, such as at night or during weekends when power consumption is relatively low. The excess electricity is used to pump water from a lower reservoir to an upper reservoir. Then, during periods of high demand or peak load, the stored water is released to flow downhill through turbines, generating electricity and supplying it back to the grid. This process allows energy to be stored when the demand is low and released when the demand is high. It is found that using a battery bank, the energy can be stored and supplied to the Load to reduce the peak load of the respective Distributon Transformer. The installation of BESS at the point of existence of DT has been modelled and the simulation results obtained. The installation of BESS helps to reduce the peak loading of the DT including overloading and helps prevent the outage of the transformer. Based on the simulation results, a BESS of maximum 100kW, 2000Ah installed at the point of connection of DT of 200kVA results in number of overloading reduced from 264 kW to 180 kW. The simulation shows that the number of transformer outage is expected to decrease from 20.83% before the installation of BESS to 3% after the installation. Further, there will be a reduction in power and energy losses in the system as during the peak load condition, part of the load can be shared by the BESS which results in power loss reduction maximum of 84 kW and annual energy loss of 76.650 MWh at 50 percent annual peaking with daily hours. The voltage profile improvement is another front with voltage improving from 0.93 pu to 1.00 pu during peak load condition. Considering the fact that voltage plays crucial role in satisfactory operations of various household, commercial and industrial appliances, this has to be taken into account when deciding on techno-economical analysis of the proposed scheme. Under the assumptions for this research, the proposed scheme is potentially beneficial not only from technical aspects but also economical aspect as well. The investment cost of the BESS and inverter considered in the study at present value is NPR 530,000.00 whereas the monetaroy value of the energy saved annually has been found to be NPR 267062.00 for 90% overloading and peak time electricity cost of NPR 15.00 per kWh. Even for lower overloading percentage of 20 to 40 % of the rating of the DTs, the proposed scheme may be economically viable.