During a restoration effort, what is the maximum percentage increase that the BES can operate above nominal voltage?

In the context of Bulk Electric System (BES) operations during restoration efforts, the maximum allowable percentage increase above nominal voltage is essential for ensuring system reliability and preventing damage to equipment. The BES guidelines dictate that during restoration periods, voltages can be permitted to exceed the nominal values by a specific margin to ensure that the system remains stable as load conditions fluctuate and generation resources are brought back online.

The correct choice, which allows for a 10% increase above nominal voltage, reflects a balance between operational flexibility during restoration and the need to avoid voltage levels that could lead to equipment stress or instability within the system. This limit ensures that while operators can adjust voltages to manage the system effectively, they do not exceed thresholds that might introduce risk to the equipment or the reliability of service.

Higher percentages, such as 15% or 20%, would typically be considered too high during normal operations as they could exceed manufacturer specifications for equipment tolerance, risking equipment overstress or failure. Thus, a 10% increase is an accepted practice that aligns with established protocols for safely managing the BES during restoration activities.