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Substation circuit breakers and other equipment are sized to withstand the maximum anticipated short-circuit currents. Although the short-circuit analysis used to design a substation takes into account the expected expansion of the network, over time the maximum short-circuit current, especially for certain operating conditions, can exceed the circuit breaker ratings. As upgrading the equipment is expensive, the life of the present equipment can be extended if these violation conditions can be identified in real time and operational actions taken to mitigate them. In this study, the authors present a method for on-line short-circuit analysis and a method for determining preventive action using transmission line switching.