What are voltage variations that fall outside the allowable range?

The correct response encompasses a range of voltage variations that can negatively impact electrical systems. Voltage sags refer to short-duration decreases in voltage, often caused by increased demand or faults in the system. Voltage swells are temporarily elevated voltages that can occur due to sudden load reductions or capacitor switching. Transients are brief voltage spikes that can result from switching operations or lightning strikes. Together, these variations are classified as disturbances that fall outside the permissible voltage limits set by utility standards. Understanding this range is essential for ensuring the stability and reliability of power systems, as each type of variation can lead to equipment malfunction or failure if not properly managed.