Power system planning studies on a real utility system

In a power system, a contingency refers to an outage of power system components such as transformers, generators, lines, etc. due to faults or failure. A contingency could lead to voltage and power flow problems. This paper describes practical contingency studies based on a real power system provided by a utility. The aim of this study is to find out contingencies that cause under voltage, over voltage or overloading problems. Once the trouble causing contingencies are identified, a violation mitigation process is carried out to eliminate the voltage and flow violations. The critical load level, defined as the load level below which the violations disappear, is determined. Contingency studies involving spare transformers are also performed to verify whether spare transformers will meet the design specifications if they replace the transformers in service. A study called MW-Mile calculation for the system is also performed for reliability evaluation purposes.