これまで我が国の電力系統では，電力需要の堅調な伸びrnを背景に，年ごとに一定量の設備投資が行われてきた。しrnかし近年，電力需要の伸びは鈍化傾向にあると予測されてrnいる。加えて，わが国では電力市場の自由化も段階的ではrnあるが着実に進展しており，競争環境拡大の流れにある。%In this paper, a new method of estimating critical generation margin (CGM) in power systems is proposed from the viewpoint of transient stability diagnostic. The proposed method has the capability to directly compute the stability limit output for a given contingency based on transient energy function method (TEF). Since CGM can be directly obtained by the limit output using estimated P-θ curves and is easy to understand, it is more useful rather than conventional critical clearing time (CCT) of energy function method. The proposed method can also estimate CGM as its negative value that means unstable in present load profile, then negative CGM can be directly utilized as generator output restriction.rnThe proposed method is verified its accuracy and fast solution ability by applying to simple 3-machine model and IEEJ EAST10-machine standard model. Furthermore the useful application to severity ranking of transient stability for a lot of contingency cases is discussed by using CGM.
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