Masaki Nagata

FCL location selection in large scale power system

Maximum short circuit current of a modern power system is becoming so large that the current should be reduced to make more efficient use of power system transmission capability. The fault current limiter (FCL) is a promising solution of this problem and it can be categorized into two types: constant impedance type FCL and current limiting type FCL. Current limiting type FCL such as rectifier type superconducting FCL (RSFCL) has variable equivalent impedance depending on the limit of the current through FCL and power system impedances. In this paper, a method is proposed to incorporate RSFCL into short circuit current analysis, which is needed to evaluate the effectiveness of FCL installed in a large scale power system. Also, an efficient method to find FCL locations suitable for reduction of short circuit currents of more than one fault location is developed. The efficiency and effectiveness of these methods are shown by numerical examples.

An energy function based contingency screening method for ATC assessment with transient stability constraints

For the effective use of power system under the deregulated environment, it is important to make a fast and accurate evaluation of the maximum available transfer capability (ATC) from a supply point to a demand point. An ATC assessment requires (n-1) security assessment under multiple supply/demand scenarios. An ATC assessment with transient stability constraints (transient stability ATC) involves a huge computational burden and has a dominant part in overall computational cost of ATC assessment. In this paper, a novel contingency screening method for transient stability ATC assessment is proposed, which utilizes a contingency severity index obtained by an energy function approach. This severity index takes into account the influence of the transaction under study on severity of contingencies. Numerical example shows that the proposed method is proven to be an efficient method to find the severest contingencies from the viewpoint of ATC assessment.