Fast turbine valving

Abstract

The fact that, as a matter of necessity, power system steam turbines are in all cases equipped with control systems which include provision to close steam inlet valves rapidly on sudden loss of load as a way to suitably limit speed increase, implies that these systems are basically not difficult to modify so as to allow employment of fast valving as a way to maintain system stability despite the occurrence of a line fault or some other system stability endangering event. Advantageous use of fast valving as a way to improve system stability requires provision for fastest feasible initiation of intercepting valve closure followed by a promptly initiated and initially rapid process of reopening, and preferably also provision within steam sources to allow effecting sustained partial closure of control valves without causing the opening of high pressure safety valves. To gain speed and selectivity initiation of valving needs to be made responsive to fault relaying systems and by this means responsive also the location and type of fault, and can also advantageously take into account prefault conditions. Attention is directed to the fact that design aspects of turbine overspeed protection systems can influence the occurrence and extent of inter-area break-up that sometimes takes place when an area of a system or interconnection experiences a sudden net loss of export load as a result of the opening of area tie lines. Cost aspects of providing trip to auxiliary load are reviewed. Copyright © 1973 by The Institute of Electrical and Electronics Engineers, Inc.