In power system operation, what does reactive power primarily affect?

Reactive power primarily affects voltage stability in power systems. In electrical systems, reactive power is necessary to maintain voltage levels within acceptable limits across the network. It does not contribute to the actual work done (real power) but is crucial for creating and sustaining electric and magnetic fields in equipment such as transformers, motors, and transmission lines.

When there is not enough reactive power available, voltage levels can drop, leading to instability in the system. This can create conditions where some parts of the grid may experience voltage sags, potentially causing equipment malfunction and even cascading failures across the system. Maintaining adequate reactive power levels is essential for ensuring that voltage remains stable during varying loads and operational conditions.

The other options relate to important aspects of power systems but do not capture the primary impact of reactive power as effectively as voltage stability does. While current distribution, efficiency of transformers, and power factor improvement are relevant considerations in power system operation, they are not as directly influenced by reactive power as voltage stability is.