Substation voltage upgrading

Needs, practices, and possibilities for substation voltage are discussed. The survey of US utilities shows significant activities in upgrading stations with operating voltages below 242 kV. The review of standards governing the present practices reveals substantially larger margins in insulation levels with lower voltages. If the BIL of substations rated below 242 kV is decreased by two steps, the margin will still be the same or better than that of 800 kV substations. Furthermore, applications of ZnO arresters allows substantial decrease in minimum clearances. A need for revision of presently required insulation levels and clearances for substations in the lower voltage range is identified