What equipment shall each Balancing Authority (BA) have available to assist the system operator in maintaining voltage within established limits?

Each Balancing Authority (BA) must have capacitance and reactive devices readily available because these are essential for managing the voltage levels in the electrical grid. Reactive power plays a crucial role in voltage control, as it helps to maintain voltage stability and provides the necessary support during fluctuations in demand or supply.

Capacitors and other reactive power devices can either supply reactive power when there’s a deficit or absorb it when there's an excess, thereby ensuring that voltage remains within the established operational limits. This capability is critical for the BA to perform its function effectively, particularly in maintaining balance between generation and load, which directly impacts the reliability and efficiency of the transmission system.

While transmission breakers and switches, distribution breakers and switches, and tie-line and major load feeders are important elements of the overall system, they primarily deal with the control and distribution of power rather than the specific function of maintaining voltage levels. Hence, the availability of capacitance and reactive devices is the most direct and relevant requirement for this purpose.