Inertia in a power system comes from the rotating mass of large synchronous machines (like those in thermal and hydropower plants). This rotating mass resists changes in frequency, helping to stabilize the system during disturbances (e.g., sudden loss of generation or load).
What is a Low Inertia System?
A low inertia system has less rotational mass connected to the grid. This typically happens when:
- Large thermal or hydro generators are offline or decommissioned.
- Renewable sources like solar PV and wind (especially inverter-based ones) replace them.
- The share of non-synchronous generation increases.
Specific Situation in small countries:-
Small country’s power system is a relatively small and isolated grid, which makes it more vulnerable to frequency instability.
Key factors contributing to low inertia:–
- High penetration of renewables: Solar and wind are increasing, but they do not inherently provide inertia.
- Retirement or low dispatch of large thermal units: Especially during high hydro seasons or times of low demand.
- No interconnection with neighboring grids: Unlike continental grids, small countries cannot rely on external support for frequency regulation.
Stability Issues Arising from Low Inertia - Faster Rate of Change of Frequency (RoCoF):
In a low inertia system, frequency changes more rapidly after a disturbance.
This gives less time for protection and control systems to react, risking blackouts. - Increased risk of Under Frequency Load Shedding (UFLS):
Because frequency can drop more suddenly, automatic load shedding schemes might not activate quickly enough. - Reduced effectiveness of traditional frequency response mechanisms:
Slower-responding hydro or thermal plants can’t stabilize the grid quickly.