Security assessment in the electricity market environment

Summary form only given as follows. Security assessment has always played an important role in system operation, and has always been one of the most computationally expensive calculations in the control center. The new RTO models require the solution of very large systems of unprecedented size. Simulating systems of these sizes impose additional computational challenges and are affected by model accuracy, solution techniques and system architecture. The concept of "n-1" security is a requirement in the context of the uncertain electricity market environment. So several contingencies and monitored facilities must be included as part of the optimization techniques to guarantee "n-1" security, and to relieve constraints during the congestion management process. Model accuracy and validity becomes a major issue when dealing with very large databases. Since these databases are created by merging databases of various transmission companies, the overall model needs to be checked and validated to a greater degree than in the past. One of the basic functions of the spot/balancing and congestion management markets, is a bid-based security constrained economic dispatch, which considers real-time system balancing and re-dispatch to avoid congestion and maintain flows and constraints under several contingencies and limits. Given an operating condition, a single contingency could determine the limits on the transmission network, and branch power flows may be bound by its impact in the event the contingency takes place. Post-contingency analysis is used to identify the set of binding constraints for the optimization loop, therefore anticipated contingencies can limit the system at all times. Security assessment gets more complicated if the market deals with day-ahead hourly schedules, where participants will buy and sell energy and transmission, settle and reconfigure financial transmission rights via locational marginal prices. In general the electricity market applications are b- ased on a combination of optimization methods and efficient load flow solutions for realtime as well as day-ahead calculations. This will demand considerable computational time, paving the way to distributed and parallel processing. On-line and day-ahead voltage security has been implemented considering the use of more than one processor, but the voltage security constraints have not been implemented yet as part of the security constrained dispatch. Validity of the network models, faster algorithmic solutions, efficient data exchange and client/server distributed architecture are keys to providing security assessment in the electricity market environment.