Switching Operation by Considering Customer Daily Load Patterns

Summary With the rapid load growth and the delay of construction of new substations and feeders in Taiwan Power (Taipower) distribution system due to land acquisition problem, the electricity service curtailment has to be performed to reduce system peak loading during summer season. Besides, feeder and main transformer overloading and fault contingencies are frequently occurred during heavy load period. To solve the problem, load transfer among feeders and main transformers is usually executed by inter-feeder switching operations to meet the system load and operation reliability requirements. However, since the loading of distribution systems varies with time of day, day of week, and season because of the load behavior of the customers served, the feeder/main transformer overloading might be occurred again within a short period of time after a series of switching operations to solve a system contingency if the switching decision is determined without considering the variation of load profiles in the following hours. Methodology for inter-feeder load transfer enhanced by considering the customer daily profile is presented in this paper. In this approach, the daily load profiles of distribution systems are investigated by considering the typical daily load patterns, data in the customer information system (CIS), and data in the outage management information system (OMIS). Typical daily load patterns of various customer classes have been determined by the load survey and are exploited to derive the load profiles of each service sections of distribution feeders. The monthly energy consumption and the types of the customers in CIS are used to determine the loading profiles of the customers. For each service section the distribution transformers deployed, the customers served within the section are identified by the information in the OMIS of Taipower. By this way, the daily load profiles of the distribution transformers, the service sections, the feeders, and the main transformers in the substations are determined to evaluate the hourly loading during the whole day. The growth rate of customer loading is taken into account by considering the historical records of the customer power consumption in CIS. In this study, load profiles of nine customer classes for both the working day and weekends of four seasons are studied for the inter-feeder switching operations.