Decoupled substation reliability assessment

Distribution reliability studies usually involve a detailed model of the substation feeder and all of its sub-feeder elements. Load point indices are gathered at each of the customer locations and composite system wide indices are found based on all of the load point indices. In most of these reliability studies there is little detail given for the substation. Often times the substation is either represented by a transformer and a breaker or just a breaker. Typical substation outage events can contribute up to 20% of customer interruptions [Brown, RE. Electric power distribution reliability. New York: Marcel Dekker; 2002]. Therefore, it is important to have a detailed model of the substation included in distribution reliability studies to get accurate results. Including a detailed substation model in distribution reliability studies can greatly increase the size and complexity of the entire system model. One possible solution to this problem is to separate the substation reliability analysis from the distribution feeder reliability analysis. This would allow the use of specialized tools on the substation reliability analysis, while keeping the size and complexity down. It would also allow the use of existing software available for the distribution reliability analysis. In many companies the same substation arrangement is used multiple times throughout their system, so they would only need to model the substations once.