Which type of power plant is prioritized for stability when restoring the system?

Hydroelectric units are prioritized for stability when restoring the system because they have the unique capability to provide immediate and controllable power output, which is essential in restoring balance to the electrical grid. Hydroelectric plants can quickly ramp up output or reduce their generation as needed, making them highly responsive to fluctuations in demand or supply during system disturbances.

Additionally, hydroelectric plants can offer ancillary services such as frequency regulation and reactive power support, which are crucial for maintaining system stability. Their ability to start and synchronize efficiently with the grid enhances their role in system recovery following outages or disturbances.

In contrast, while gas turbine units can provide rapid start-up times and flexibility, they may not offer the same level of inertia or support for frequency stability as hydroelectric units. Nuclear power plants, though stable in output, generally cannot adjust their output quickly due to operational constraints, making them less effective during restoration scenarios. Wind farms, although renewable and increasingly important for the grid, have variable output based on weather conditions and generally lack the immediate dispatchability required for system restoration. Therefore, hydroelectric units emerge as the preferred choice for stabilizing and restoring the power system.