Criteria for load control when considering static stability limits

A load control scheme, such as under voltage load shedding or UVLS, is generally applied as a safety net measure in situations where system collapse is anticipated and can potentially result in blackout conditions. Recently, in several electricity markets, load control schemes are being proposed for system stability where some type of economic incentive is used to have customers reduce demand for short periods of time. While UVLS designs generally shed load at a substation level, market-based load control schemes potentially allow for an enhancement of both market efficiency as well as of system reliability as the type of load being shed and the location where load is to be shed are hand-picked at the end-user or at the customer-level. A prioritization of preferred load types and preferred locations where if load control were applied, would provide a more efficient ancillary service. This paper proposes a discriminatory load shedding scheme to be incorporated as part of an ancillary services market design based upon the type of load and the location of load towards increasing the system static stability margin.