Load control for improving system security and economics

Restructured markets are rarely flawless: the expected price reduction frequently has not been achieved and the system is often operated closer to its limits, with smaller margins on security, reliability and reserve. Thus, it is necessary to find out new resources to reduce price spikes and volatility, to improve transient stability and congestion management, to increase transfer capacity and to provide ancillary services. Loads that can be interrupted and/or controlled may prove to be profitable for each one of these purposes. This paper presents and discusses the potential benefits provided by the so-called interruptible loads (IL) to the electric system. Some simulations have been run on the Italian network and on a test system to show how ILs can be a means of increasing the transfer capacity of interconnection lines and how they can compete with generators as ancillary service providers for primary and secondary P/f regulation.