What action should be taken to reduce crosscurrents if the bus voltage is high and the power factors are the same?

When dealing with high bus voltage and the same power factors, lowering the voltage to all units is the correct action to take in order to reduce crosscurrents. High voltage can create imbalances in the system, leading to undesirable interactions, or crosscurrents, among generators. By lowering the voltage, you can mitigate these effects and promote better synchronization among the units.

This action helps in maintaining system stability and ensures that all generators operate more efficiently within their designed parameters. Lowering the voltage aligns the operation of the generators more closely, thus reducing the likelihood of crosscurrents that can arise from differing voltage levels or reactive power outputs.

The other options, such as increasing generator output or disconnecting generators, could exacerbate the situation or lead to a lack of supply stability. Increasing synchronization would typically be an action taken to improve coordination but may not address the immediate issue of high voltage causing crosscurrents. Thus, reducing the voltage is the most effective approach.