Impedance Method Used To Calculate Initial Switching Currents in Transmission Networks and Generator Real Power

Jan Machowski, Piotr Kacejko, Piotr Miller


Switching-on of transmission network elements can bring about high inrush currents in the network elements (lines and transformers) as well as sudden changes in real power of generating units. In order to reduce those disadvantageous effects in modern power systems switching operations are controlled by protection devices referred to as synchro-check. Optimal setting of the synchro-check parameters requires the application of adequate criteria and an efficient method for calculating current changes in lines and generators that result from switching operations. This article proposes a new calculation method based on a nodal impedance matrix. Such a matrix is commonly used for short-circuit analyses. The advantage of the proposed method is that a short-circuit software with an adequate extension can be also applied to the analysis of switching operations.


initial switching current, switching operations, synchro-check

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