Critical-Load Prioritization

When generation is constrained, an installation protects its mission by shedding non-critical demand in a pre-planned order.

Not all load is equal

In an islanded or degraded state, the installation may not be able to power everything. Continuity depends on knowing, in advance, which loads must never drop and which can be shed. Critical-load prioritization is the ranked plan that lets the microgrid controller protect the mission automatically.

Tiers of load

Loads are grouped into tiers: life-safety and mission-critical systems that must stay energised; important-but-interruptible loads that can be dropped briefly; and deferrable loads that can be shed for the duration. The controller sheds from the bottom up as generation margin shrinks, and restores from the top down as it recovers.

• Tier 1: life-safety and mission-critical — never shed
• Tier 2: important but briefly interruptible
• Tier 3: deferrable — shed first, restore last
• Automatic, pre-planned, executed by the microgrid controller

Why it protects the availability gate

Because a unit can trip (single-unit availability 0.86–0.995), the installation may temporarily have less generation than total demand. Prioritization ensures that when that happens, the shortfall is taken by deferrable loads, never by the mission. It is the software counterpart to physical redundancy.

Prioritization is configured per installation to match its mission, and it is exercised regularly in drills so that when a real shortfall arrives the shedding and restoration behave exactly as planned rather than being tested for the first time under stress. Restoration follows the reverse order and is rate-limited, so that reconnecting shed load does not itself cause a surge that re-trips the island — a detail that matters as much as the shedding logic.