For how long shall sources be paralleled during seamless transfers to facilitate load transfer?

During seamless transfers of power sources, such as switching from one generator to another while maintaining power to the load, the paralleled connection should generally be maintained for no more than 1 second. This short time limit helps to minimize the risk of synchronization issues, voltage fluctuations, and potential damage to equipment.

In seamless transfer operations, it is crucial to ensure that both power sources are in phase and at similar voltage levels to avoid creating electrical arcs or other disturbances that can affect both the generators and the electrical system they are supplying. The shorter the duration of the parallel operation, the lower the chance of encountering significant phase mismatch or transmission instability.

Since the other choices suggest longer durations, they would not be ideal for seamless transfers, as longer parallel connections could increase the likelihood of complications such as phase differences and power quality issues. The safest and most efficient practice is to limit the paralleling of sources to the shortest time necessary for the transfer, which is why maintaining this limit at 1 second is the best approach.