Improving Transformers´ Utilization Under Single Contingency Policy and Customer Reliability Requirements

During the past two decades, utilities have saved tremendous capital investments in new transformers by improving utilization of existing transformers in distribution systems. Meanwhile, in these highly-utilized systems, deteriorated reliability has been observed at the end-user level. This is mainly because utilities determine transformer utilization conventionally through the N-1 approach, which only guarantees reliability at the system level but not reliability requirements of customers. This paper presents an innovative method that balances the financial interest of utilities and service quality of customers by maximizing transformers´ utilization while assuring reliability at the end-user level. The proposed method´s advantages are enhanced by its capability of handling customer reliability requirements of a whole distribution system and/or of designated locations with critical loads. In addition to determining the maximum utilization of transformers, the proposed method can be extensively applied to other power delivery equipment in distribution systems.