Voltage restored in the event of a three-phase terminal fault
HV electrical switchgear. Appendices

The restored voltage is calculated using the system of symmetrical direct, inverse and homopolar components (indices d, i and 0) [10][11] .

This method, published in 1918 by C.L. Fortescue, solves the problem of calculating current distribution in unbalanced polyphase networks.

It is also a relatively simple way of determining the restored voltage (or pole factor) when each pole of a circuit-breaker is disconnected. The TTR can then be deduced by multiplying the peak value of the restored voltage by the amplitude factor.

This calculation is detailed here because it is difficult to find the complete determination of pole factors (ratio between the voltage restored on a pole and the voltage between phase...