New index for frequency deviation security assessment

Frequency is an important physical quantity reflecting security, stability, and power quality state of power systems. A new security index for transient frequency deviation assessment(FDSA) was presented. A set of two-element limitation tables were used to describe transient frequency deviation acceptability of individual bus or generator, and the security margin index was defined based on the relationship of frequency time response curve and given frequency deviation threshold. Specific treatment was applied to ensure the continuity of the index in the overall frequency changing scope. The characteristics of the proposed security index were analyzed on a provincial power system. Numerical results show that the index´s monotonicity and smoothness are very good, and the computation is simple.