http://onlinelibrary.wiley.com/doi/10.1002/etep.4450120408/a...

Abstract
During power system restoration, it is necessary to check the phase angle between two buses before closing circuit breakers to connect a line between them. These angles may occur across a tie line between two systems or between two connected subsystems within a system. In case of large Standing Phase Angle (SPA) difference the synchro-check relay does not allow closing of the breaker for this line. Therefore, this excessive SPA has to be reduced before attempting to connect the line. In this paper a new and fast method for reducing SPA is presented. For this purpose, the standing phase angle difference between two specific buses is represented in terms of sensitivity factors associated with the change in active power generations and consumption at the buses. Then, the proposed method reschedule generation of selected units or shed load of selected buses to reduce excessive SPA difference between two buses based on sensitivity factors.

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A formulação do equilíbrio completo do sistema é então estendida de forma a permitir o controle da defasagem angular entre duas barras do sistema através do redespacho de potência ativa para o fechamento em anel do sistema. Para melhorar o desempenho da
metodologia proposta, é descrito um procedimento para determinar os fatores de sensibilidades dos geradores baseados no vetor tangente do sistema.

The total system equilibrium is also used to control the standing phase angle difference between two buses of the system using the active power redispatch. This is done in order to deal with the system loop closure problem. To improve the approach performance, a method to compute sensibility factor of generators using the tangent vector is described.