CERC's Updated Grid Code for Storage: What Every Developer Must Comply With

India's central grid regulator, the Central Electricity Regulatory Commission (CERC), has issued updated grid interconnection standards for Battery Energy Storage Systems. These standards — effective from Q1 2026 — apply to all new BESS projects connecting to ISTS (Interstate Transmission System) and to state grid connections above 11 kV. For any developer planning a grid-scale BESS project in India, non-compliance is not merely a regulatory inconvenience: it is a commissioning blocker.

This article summarises the key technical requirements, flags the sections most likely to affect project design, and explains how India's updated grid code compares to international benchmarks.

Why CERC Updated the Standards Now

India's grid code for storage was originally drafted in 2019 when the commercial grid-scale BESS market was nascent. The code addressed basic interconnection requirements but did not anticipate the technical complexity of large-scale storage operating in real-time ancillary service markets, nor did it address grid-forming converter behaviour, dynamic voltage support, or synthetic inertia provision — capabilities now expected of modern BESS installations.

The 2026 revision responds to three specific pressures: SECI's expanded BESS procurement programme, PGCIL's evolving grid stability requirements as variable renewable penetration rises above 25% on several regional grids, and incidents in 2024–2025 where poorly commissioned BESS systems tripped during grid disturbances due to inadequate protection coordination.

The result is a more demanding technical standard — closer to the ENTSO-E or NERC NERC-PRC grid code family than India's previous lightly specified regime.

Key Technical Requirements

1. Frequency Response (ROCOF and Nadir Compliance)

Under the updated code, BESS systems above 10 MW must provide fast frequency response within 500 milliseconds of detecting a frequency deviation exceeding ±0.1 Hz from 50.0 Hz. Full active power output must be achieved within 1 second.

The code also introduces Rate of Change of Frequency (ROCOF) ride-through: BESS must remain connected and actively respond during grid events where ROCOF exceeds 0.5 Hz/s, up to a maximum of 2.0 Hz/s for a period of 500 ms. Previous Indian grid codes did not specify ROCOF thresholds for storage.

This requirement directly affects inverter selection. Standard grid-following inverters with default ROCOF trip settings — typically configured for European grid codes — will trip at 0.5 Hz/s or lower. Developers must verify that their selected PCS (Power Conversion System) has configurable ROCOF thresholds and has been tested to the updated Indian code profile.

2. Low Voltage Ride-Through (LVRT)

The updated code requires BESS to remain connected during three-phase fault conditions that reduce terminal voltage to as low as 0% for up to 150 milliseconds, recovering to 85% within 1,500 milliseconds. During LVRT, the system must inject reactive current at a rate of at least 2% of rated current per 1% of voltage drop below 90% nominal.

This reactive current injection requirement — a reactive support obligation during fault events — is new to India's storage grid code and aligns with European practice. It requires that PCS control systems support reactive current boost mode with programmable slopes. Many basic inverters designed for industrial UPS applications do not support this; utility-grade PCS designed for grid-scale storage does.

3. Reactive Power and Power Factor

BESS systems must maintain a power factor capability range of 0.9 leading to 0.9 lagging at full active power output. The grid operator may issue real-time reactive power setpoints within this range, and the BESS must track setpoints within ±5% within 1 cycle (20 ms at 50 Hz).

For developers using PCS equipment without reactive power autonomy — or with fixed power factor configurations — this represents a retrofit or replacement requirement.

4. Protection Coordination

The code mandates that protection relay settings for BESS grid connections be coordinated with the upstream substation's protection scheme, with evidence of coordination submitted to the relevant transmission utility as part of the commissioning documentation package.

Specific requirements include:

• Distance relay Zone 1 reach calibrated to the BESS interconnection transformer impedance
• Differential protection on the interconnection transformer (required for transformers above 2 MVA)
• Earth fault protection with response time below 200 ms for bolted three-phase faults
• Islanding detection per IEEE 1547-2018 (anti-islanding) with configurable thresholds

The requirement for documentation submission and utility sign-off on protection coordination is the most practically significant change for project timelines. Protection coordination studies must be commissioned early — ideally at 60% engineering completion — to avoid commissioning delays.

5. Communication and SCADA Integration

BESS systems above 5 MW must implement IEC 61850 GOOSE messaging for protection tripping and SCADA telemetry at a minimum update rate of 1 second. For ISTS-connected projects, PGCIL's NLDC (National Load Dispatch Centre) telemetry requirements apply additionally, requiring dual independent communication paths.

State Dispatch Centres (SLDCs) may have additional communication specifications. Developers should confirm SLDC requirements early, as some SLDCs still require MODBUS RTU or DNP3 in addition to IEC 61850 — adding communication gateway hardware to the project scope.

6. Metering Standards

Revenue metering for BESS must comply with CEA (Installation and Operation of Meters) Amendment Regulations 2023. The key change from the developer perspective: separate meters are required for charge and discharge energy, and the meter accuracy class for storage must be Class 0.2S (versus Class 0.5 previously acceptable for RE generation). Class 0.2S meters are approximately 3x the cost of Class 0.5 meters — a minor cost increment but one that affects procurement lists.

What Has Not Changed

Despite the updated code, several provisions that concerned developers before the revision remain unchanged or were addressed less stringently than expected:

• Ambient temperature derating requirements are not mandated in the grid code itself — they remain a commercial warranty matter between the developer and equipment supplier
• Cycle degradation disclosure to the grid operator is not required (though CERC's draft regulation on secondary frequency reserves may introduce performance reporting requirements in a future amendment)
• State-level connections below 11 kV remain under state SERC jurisdiction, with variable standards

Practical Implications for Project Design

The updated grid code will affect projects at three stages:

1. Equipment specification: PCS must support configurable ROCOF thresholds, reactive current boost, and IEC 61850. Specify this explicitly in equipment RFPs — not all vendors default to Indian grid code profiles.

2. Engineering scope: Protection coordination studies must be scoped early. Budget 4–6 weeks for a protection coordination study from a qualified protection engineer, plus utility review time of 6–8 weeks. This is often the longest single path item in commissioning.

3. Commissioning documentation: The updated code requires a Factory Acceptance Test (FAT) report certifying LVRT and frequency response capability before grid connection. FAT must be conducted by an accredited testing body. Build 4–6 weeks for FAT into project schedules.

International Comparison

India's 2026 grid code for BESS now broadly aligns with:

• Germany (VDE-AR-N 4105): LVRT requirement is equivalent; reactive power range is broader in Germany (0.95 to unity at partial load)
• UK (G99): ROCOF ride-through to 2.0 Hz/s is now matched by India; UK still requires 1.0 Hz/s minimum
• Australia (NER, AEMO SIPS): Australia specifies FFR response within 150 ms; India's 500 ms is more relaxed

For developers importing BESS systems certified to European grid codes, India's 2026 standard should be achievable without hardware changes in most cases — but firmware reconfiguration and retesting to Indian-specific profiles will be required.

SilicIndia Energies' BESS systems are designed and tested to the 2026 CERC grid code requirements, including LVRT, ROCOF ride-through, and IEC 61850 communication. Our commissioning documentation package includes the protection coordination study template, SCADA integration checklist, and FAT report format required for PGCIL/SLDC approvals. Contact our engineering team for project-specific compliance support.