Reliability analysis of electric utility SCADA systems

Electric utility SCADA systems must be highly reliable given the potential for the SCADA system to directly contribute to load curtailment. This paper presents an analysis of SCADA system reliability in terms of its expected, aggregate contribution to load curtailment on the power system. Expressing this aggregate in system minutes and applying an appropriate damage cost function then provides an annual cost measure of SCADA system reliability worth. A composite generation and transmission system reliability evaluation technique is used to perform the numerical analysis of the joint SCADA and power system model. This performs a Monte Carlo simulation and includes an optimal power flow for enumerating grid load curtailment states and analysis of SCADA system component connectivity to determine availability of SCADA control. The application of this analysis is illustrated in a comparison of two alternative SCADA architectures. Trans Power (New Zealand) has adopted a subtransmission SCADA architecture which utilises terminals operating off its national SCADA system. These terminals have replaced separate systems located in each area. The objective of the evaluation being to quantify the increased exposure to financial losses due to joint load curtailment.