Preparing India's RE Dominated Power Grid for Atmospheric Shocks

The recent large-scale power outages in the Iberian Peninsula (2025) and Texas (2021) underscore the urgent need to strengthen grid stability as countries transition to high shares of Variable Renewable Energy (VRE).

On April 28, 2025, the Iberian blackout was triggered by the abrupt loss of nearly 15 GW—approximately 60% of Spain’s electricity supply—within just five seconds. The resulting frequency collapse, compounded by low system inertia due to high VRE penetration, caused widespread disruptions across Spain, Portugal, and parts of France. Critical infrastructure was impacted, including railway networks and communication systems, with estimated economic losses reaching €1.6 billion.

Similarly, during Winter Storm Uri in February 2021, Texas faced a severe power crisis that revealed deep structural vulnerabilities in its energy system. The extreme cold wave caused a simultaneous spike in electricity demand and failure of multiple generation sources, including natural gas plants and wind turbines, due to inadequate winterization. The prolonged outage affected more than 4.5 million customers, lasted for days, and led to at least 246 fatalities, with economic losses estimated at $195 billion, making it one of the costliest energy disasters in U.S. history.

Both events demonstrate how reduced inertia in high-VRE grids compromises the system’s ability to absorb and recover from sudden disturbances, especially during extreme weather events. These blackouts serve as a stark warning that grid resilience, proactive infrastructure planning, and climate-proofing of energy assets are indispensable for secure and sustainable power systems in the renewable era.

Status and Preparedness in India

1. Introduction

The rapid integration of Variable Renewable Energy (VRE) into power systems is introducing a new set of operational challenges, primarily due to the intermittent and weather-dependent nature of sources like solar and wind. A growing concern is the emergence of wild grid swings—sudden, large fluctuations in system frequency and voltage—often triggered by atmospheric disturbances such as cloud cover, wind variability, or storms. These swings are further amplified by the erosion of system inertia, as conventional synchronous generators are increasingly replaced by inverter-based resources that do not inherently provide the stabilizing effects needed to dampen frequency deviations.

2. What Are Wild Grid Swings?

Wild grid swings are large, abrupt deviations in frequency (and sometimes voltage) caused by:

- Sudden loss or gain of generation due to atmospheric changes

- Weak frequency containment due to low inertia

- High RoCoF (Rate of Change of Frequency) that impairs grid operator response

4. Importance of Inertia in Grid Stability

A. What Is Inertia?

Inertia plays a fundamental role in maintaining grid stability by resisting sudden changes in frequency. It is derived from the rotational kinetic energy stored in the spinning masses of synchronous generators, such as those in coal, hydro, and gas power plants. When there is a sudden mismatch between electricity supply and demand—such as a generator tripping or a large load entering the system—this inertia acts as an immediate buffer. It releases stored kinetic energy almost instantaneously, thereby slowing the Rate of Change of Frequency (RoCoF). This delay is crucial, as it provides a narrow but vital window of time, often just a few seconds—for automated control systems, reserves, and grid operators to detect the disturbance and initiate corrective actions, such as ramping up other generators or activating fast reserves like batteries. Without adequate inertia, the grid becomes more vulnerable to rapid frequency deviations, increasing the risk of equipment damage, load shedding, or even widespread blackouts.

B. Low Inertia in VRE Grids

- Wind/solar inverters decouple generation from grid inertia.

- High VRE penetration leads to low system inertia, higher RoCoF, and increased instability risk.

5. Status of Preparedness in India

India is making significant progress toward its ambitious target of achieving 500 GW of non-fossil fuel capacity—accounting for approximately 62.5% of the projected 800 GW total installed capacity by 2030. The Indian Electricity Grid Code (IEGC) 2023, notified by the Central Electricity Regulatory Commission (CERC), addresses the challenges posed by the increasing penetration of Variable Renewable Energy (VRE) sources, particularly concerning the Rate of Change of Frequency (RoCoF). While the IEGC does not specify explicit numerical thresholds for RoCoF, it emphasizes the importance of frequency stability and outlines provisions to manage rapid frequency deviations.

Key Provisions Related to RoCoF in IEGC 2023:

a). Primary Frequency Response Requirements:

- Generating stations above 10 MW connected at 33 kV and above must:

- Be equipped with governors or frequency controllers operating at a drop of 3% to 6% and a dead band ≤ ±0.03 Hz.

- Provide real power primary frequency response within 1 second when frequency deviates > 0.3 Hz.

- Operate frequency regulation over a range from 10% to 100% of maximum active power.

- Limit power ramp rate to ±10% per minute.

b) Inertia and RoCoF Considerations:

- The IEGC acknowledges that declining system inertia due to inverter-based VRE leads to higher RoCoF.

- While no numeric RoCoF limits are specified, the code emphasizes the need for synthetic inertia and fast frequency response mechanisms.

c) Under-Frequency Load Shedding (UFLS):

- UFLS schemes are sensitive to RoCoF and designed to arrest frequency decline.

- Example: df/dt-based load shedding may trigger at a RoCoF of -0.1 Hz/sec when frequency falls to 49.9 Hz.

While the IEGC 2023 stops short of defining RoCoF thresholds, it provides a regulatory framework to address frequency stability in a high-VRE scenario. The emphasis on enhanced primary response, acknowledgment of inertia challenges, and incorporation of RoCoF-sensitive UFLS mechanisms signal a shift towards modern, adaptive grid management practices essential for India’s renewable energy future.

However, despite this momentum, there remain critical gaps in system preparedness to manage the operational complexities of a high-VRE, low-inertia power system.

The following assessment outlines the status across key dimensions:

A. Inertia Monitoring & Estimation

- POSOCO began inertia estimation in 2021 using real-time RoCoF-based techniques.

- Dynamic inertia monitoring dashboards are under development but not yet integrated into dispatch centers.

B. Frequency Response Standards for VRE

- No mandatory synthetic inertia or fast frequency response (FFR) requirements yet in national grid codes.

- CERC’s Ancillary Services Regulations (2022) allow BESS and hydro to participate in reserves but do not mandate VRE to provide FFR.

- IEGC proposed Frequency Response obligations for VRE implementation is pending.

C. Grid-Forming Inverter Readiness

- Pilot projects are under consideration (e.g., in Ladakh and remote islands) for grid-forming inverters.

- No commercial deployment in the main grid; India relies heavily on grid-following inverters.

D. Battery Energy Storage Systems (BESS)

- GoI has approved BESS viability gap funding.

- SECI has floated tenders for BESS co-located with solar/wind.

- As of early 2025, <200 MWh of BESS commissioned, mostly for time-shifting, not inertia support.

E. Forecasting & Reserve Management

- RE-rich states (Tamil Nadu, Gujarat, Karnataka) have Forecasting, Scheduling, and Deviation Settlement Mechanism (F&S-DSM) regulations.

- However, real-time reserves and flexible ramping products are absent.

- Hydro and gas remain the only responsive reserves, often manually dispatched.

F. RoCoF Protection and Grid Code Updates

- Indian grid codes lack RoCoF withstand and ride-through criteria for VRE.

- No nationwide standard exists for RoCoF thresholds in inverter protection schemes.

6. Way Forward for India

A. Operational Measures

- Dynamic inertia thresholds should be enforced regionally.

- RoCoF constraints must be integrated into dispatch optimization tools.

- Automated reserve activation (AGC + FFR) needs expansion.

B. Regulatory Action

- Enforce synthetic inertia mandates on new wind/solar >10 MW.

- Finalize and implement the Draft IEGC and Grid Code updates that include inertial requirements.

C. Investment in Fast-Acting Technologies

- Fast-track procurement of BESS for FFR and primary control.

- Promote grid-forming inverters and flywheel pilot projects in VRE-dominant zones.

D. Training and Simulation

- Load dispatch centers (RLDCs, SLDCs) need RoCoF-focused training and dynamic simulations of VRE-rich scenarios.

7. Conclusion

India is advancing toward a high-renewable energy future, but the preparedness to handle low-inertia induced wild grid swings is still evolving. Atmospheric events that disrupt solar and wind output are no longer rare. Therefore, India must urgently invest in synthetic inertia, fast reserves, forecasting tools, and regulatory frameworks that ensure grid resilience amidst growing weather-linked volatility.