Digital Capability Curves Of Salient Pole Synchronous Generators

A speeding Car always displays its Prime Parameters in different Meters on its Dashboard in real time. The safety and performance limits are depicted in the background of those meters. The Stator current Vector of a synchronous machine traverses a semicircular path as the Apparent Power varies from Zero P.F. lagging load to Zero P.F. leading load. But the study of stability of a machine is of prime importance when connected with the Grid. Different parameters govern the stability and capability of that machine viz., Power angle, Field current, Stator current, Prime Mover output, Saliency limit, Direct and Quadrature Axis Reactance, etc., A Generator is capable of operating Stably within the Graphs of above Parameters without losing synchronism from the Grid. If not for the limiting factors the alternator would be operable within the contour of the semicircle. This Capability curve was first firmed up by Dr. J.H. Walker in 1950’s. Dr. Walker defined the limiting factors graphically. In this paper these graphs are digitalized and a very comprehensive Capability curves can be drawn just by entering values of X<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</inf>, X<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">q</inf>, Rated Power Factor and terminal voltage E of the Generator in p.u. It is unique in the sense that by entering 4 key values, the Capability curve gets contoured within the boundaries of above limiting factors. Larger the area contoured in the semicircle better is the capability of the machine.