Interruptible Load and Demand Response: Worldwide Picture and the Situation in Sweden

This paper reports on part of the work which have been carried out by a group of students in Electric Power Engineering, Chalmers University of Technology in Sweden, within the scope of their course on power engineering design projects during the spring semester 2006. The project has focused on the investigation of the important roles of interruptible loads in deregulated electricity markets. This paper brings about a survey of the most up-to-date programs on interruptible load programs in various electricity markets in the world, with an emphasis on the situation in Sweden. The programs are generally grouped into two broad categories: "reliability-based" program which operates in response to system contingencies and "market-based" program which is triggered by wholesale market price of electricity. It is also seen that in some markets, interruptible loads are considered as an ancillary service.