Ancillary services-reactive and voltage control

To maintain security and adequacy in a bulk power system, FERC's Order No. 888 in 1996 specified six services called ancillary services that the electrical transmission providers must provide. These six services constitute system control, reactive supply and voltage control, regulation, operating spinning reserve, operating supplemental reserve and the energy imbalance. Besides these six services, there are additional six services for which the transmission providers are not responsible. These six services constitute load following, backup supply, real power loss, dynamic scheduling, black-start capability and network stability. Despite the extensive preparations and planning by the ten electrical grid Security Councils, the combination of generation unavailability and limited transmission capability coupled with unanticipated circumstances such as extreme weather conditions could result in shortages of generation sources for reactive supply (VArs) and voltage control that could affect the security of the electric grid. This paper discusses mainly the reactive and voltage control portion of the ancillary services associated with the interconnected electric grid.