Considerations in planning for reliable electric service

To assure reliability of electric power, it is essential to have effective transmission and adequate interconnections, adherence to operating limitations, and recognition that, in spite of all that can be done, there is always the chance that an unforeseen contingency will cause system separation and possibly generator deficiency. The first consideration requires system studies to demonstrate that no single disturbance will cause cascading tripouts of lines or generators; the second may be facilitated by automatic monitoring of the system condition; the third requires automatic load shedding on low frequency.