Which energy storage component is used in the substation control house to operate key equipment if power is lost?

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When essential equipment in a substation control house must keep operating after a power loss, the energy storage solution used is DC batteries. They provide a reliable, immediate source of direct current to the control and protection circuits, giving hold-up power as soon as the AC supply drops. Control gear like relays, PLCs, and other electronics typically run on DC, so batteries—fed and charged by AC-to-DC rectifiers—keep these systems powered without delay.

AC generators would need fuel and time to start, plus they produce AC rather than the DC the control electronics prefer, so they’re not as practical for instant, steady hold-up. Flywheels offer short bursts of high power but aren’t sized for long outages in a substation setting. Capacitors can smooth transients and provide very brief energy, but they can’t sustain operation for the duration of a power outage. Thus, DC batteries are the appropriate, dependable choice.