#inverterbasedresources

India’s transmission system operators are starting to treat grid strength and inertia as front-line operational variables — not background characteristics you only worry about in planning studies.

Why? Because the Indian power system is rapidly tilting toward inverter-based generation (solar, wind, BESS, HVDC interfaces), and that transition is creating a new risk profile in parts of the network: weak-strength conditions.

In simple terms, as synchronous generation declines in relative share:

Short-circuit levels reduce (fault current becomes lower, control-shaped, and less predictable)

System inertia thins (frequency can move faster after a disturbance)

These two parameters have historically underpinned both stability and protection performance. In inverter-heavy corridors, both are changing at once — and the operational margin is tightening.

1) The inertia blind spot: no real-time visibility

A key concern flagged in this initiative is that inertia is still often treated using planning-era assumptions and indirect operational indicators.

But in inverter-dominant systems, effective inertia can swing quickly depending on dispatch patterns and what is actually online at that moment. That makes low-inertia conditions harder to detect in real time — until the system is already stressed.

So the programme is targeting an online inertia estimation tool that can continuously assess effective system inertia and signal when synthetic or adaptive support from inverters is required to maintain frequency stability.

2) Protection risk: fault signatures are changing

Protection systems are the other major pillar.

Conventional overcurrent and impedance-based relays were designed for strong grids with high, predictable fault currents. In inverter-dominated networks, fault contributions are typically limited and shaped by converter control logic, which can alter fault signatures and weaken relay sensitivity, selectivity, and coordination.

That’s why the study is looking at detailed modelling of inverter fault behaviour and testing revised protection algorithms using real-time simulation platforms — a sign that protection philosophy will need to evolve alongside grid technology.

3) Grid-following vs grid-forming: interaction matters

The programme also focuses on how grid-following and grid-forming inverters interact during faults and restoration.

Because these devices synchronize and respond differently, mixed populations can introduce new dynamic behaviours that were rare in synchronous-machine grids. Coordinating these interactions is increasingly being positioned as a prerequisite for secure high-renewable operation.

What’s being built (not just studied)

This isn’t being framed as academic work. The deliverables include:

dynamic models of low short-circuit ratio systems in PSCAD and MATLAB

tools for online inertia estimation and synthetic inertia requirement assessment

protection algorithm testing across fault scenarios — pointing toward real-time simulation and potentially hardware-linked validation

The bigger shift

The underlying signal is big: inertia and grid strength are becoming managed resources.