A Probabilistic Method Combining Electrical Energy Storage and Real-Time Thermal Ratings to Defer Network Reinforcement

When a primary substation reaches its capacity limit, the standard solution is to reinforce the network with additional circuits. Under the right conditions, the required additional peak capacity can be provided by energy storage systems (ESS), real-time thermal ratings (RTTR) or a combination of the two. We present a probabilistic method for calculating the size of an electrical energy storage system for a demand peak shaving application. The impact of both power and energy capacity are considered, along with the reliability of the energy storage and the existing overhead lines. We also consider the combination of energy storage and RTTR - taking advantage of the inherent variability in power line rating as a result of changing weather conditions - for enhancing reliability, deferring conventional reinforcement, and increasing the availability of energy storage to participate in commercial service markets. The method is demonstrated in a case study on a network with an ongoing 6-MW/10-MWh ESS innovation project.