Similar to TestTransformerFixedRatio, but this time a new branch has been added, to supply the load when the transformer breaker is open.
The voltage at the new infinite bus is the same of one at port b of the transformer, the line has little resistance and the same impedance of the transformer.
If the breaker is closed the power to the load is supplied in the same ratio by the transformer and the line (50% from the transformer and 50% from the line).
When breacker opens (time = 2 seconds), all the power is supplied by the line, and the transformer is closed on the equivalent shunt impedance.