Interconnected System Spinning Reserve Requirements

There has been a considerable amount of work done in the area of static capacity reliability evaluation in interconnected systems. The first important paper in this subject1 utilized a two dimensional probability array upon which the tie line constraints were imposed. The basic generating unit statistics in static and spinning reserve studies are fundamentally different and in the latter case the problem is a question of will the capacity immediately available to the system be capable of satisfying the load in the event of possible capacity and load changes. The possible assistance under these conditions from an interconnected system cannot therefore be neglected in determining the risk of just carrying or failing to carry the system load. In a static capacity interconnected system study, the tie line is normally rated at its nominal value. In a spinning study, the tie line rating or inter-system transfer capability will depend upon the immediate and known conditions between each system, i. e., the existing transmission configuration, the scheduled generation pattern, etc. etc. These could be quite variable even over the course of a day.