Tamil Nadu Regulator Unveils Rules for Wind and Solar Integration

The regulations will be reassessed after two years or earlier if necessary


The Tamil Nadu Electricity Regulatory Commission (TNERC) has unveiled the Forecasting, Scheduling, and Deviation Settlement and related matters for Wind and Solar Generation Regulations in 2024. These regulations will be implemented starting April 1, 2024.

The regulations are designed to support the integration of wind and solar energy into the Tamil Nadu grid, ensuring stability and security in accordance with the state grid code and relevant legislation.

To maintain system security and reliability, the state load dispatch center (SLDC) will consider forecasts of wind and solar generation for week-ahead, day-ahead, and intra-day operations, as well as longer-term forecasts for planning purposes.

The SLDC will leverage the flexibility offered by conventional generating units and the capacity of inter-grid tie-lines to incorporate wind and solar energy generation to the greatest extent possible while ensuring grid security.

These regulations are applicable to all wind and solar energy generators, including hybrid systems, in Tamil Nadu. They cover projects connected to the Intra-State Transmission System (ISTS) or distribution system, including those linked through pooling sub-stations.

The regulations also include systems using the generated power for self-consumption or sale within or outside the state, except for grid-interactive solar energy generating system projects (rooftop solar power projects) with a capacity of less than 1 MW.

The Commission will reassess these regulations after two years or earlier if necessary.

Forecasting and Scheduling Code

The forecasting and scheduling code outlines a comprehensive set of regulations for wind and solar energy generators in Tamil Nadu.

According to these regulations, generators are mandated to appoint a Qualified Coordinating Agency (QCA) to manage their forecasting and scheduling requirements. The QCA, chosen by the generators in the state, serves as a single entity governed by mutual agreements for all wind and solar generators.

Those opting out can avail of the services of the SLDC for forecasting and scheduling, with the caveat that the generators will bear responsibility for the remaining tasks assigned to the QCA.

An individual generator connected to a designated pooling sub-station may also function as a QCA or appoint a separate entity.

Regulation 5.2 mandates the appointment of a QCA within a specified timeframe, with consequences for failure leading to deviation settlement charges.

These charges escalate over time if a QCA is not appointed within 90 days. In cases where power is injected without scheduling, the SLDC takes charge of forecasting and scheduling on behalf of the generator, with deviation settlement charges applied.

QCAs are treated as state entities, requiring registration with the SLDC.

The QCA acts as a nodal agency between the SLDC and generators, handling tasks such as aggregation of scheduled generation, meter reading, and data communication. The QCA is also responsible for providing separate schedules for wind/solar generators connected to the intra-state network or pooling sub-station.

The charges for forecasting and scheduling services provided by QCAs are mutually agreed upon and paid directly by the generators. The QCA furnishes the SLDC with real-time data, technical specifications, and forecasts while also ensuring compliance with metering regulations.

The SLDC may undertake forecasting of wind and solar energy generation, engaging forecasting agencies if needed.

The financial consequences resulting from deviations from schedules based on forecasts will be the responsibility of the generators.

It is incumbent upon state entities to operate their equipment and loads in adherence to the stipulations outlined in both the Indian electricity grid code and the Tamil Nadu Electricity grid code.

Treatment of Gaming

Any deliberate misdeclaration or understatement of scheduled generation to the SLDC by the QCA, whether for its undue commercial gain, that of a generator, or to avoid risks associated with forecasts, will be regarded as gaming and constitute a violation of these regulations.

In the event of SLDC identifying gaming, such as intentional misdeclaration of scheduled generation, the QCA/generator will be obligated to pay a penalty three times the deviation charges that would have been applicable had the scheduled generation been accurately declared.

The penalty amount will be payable by the QCA/generators to the state deviation settlement mechanism pool following the procedure to be issued by the SLDC.

The SLDC may revoke the registration of the QCA upon repeated instances of misdeclaration after providing due notice.

If the scheduled generation is zero, and there is actual generation in a specific 15-minute block by the wind/solar generators, the deviation settlement charges will be collected from those generators at 125% of the capped price for such injected energy.

Deviation Settlement for Intra-State Transactions                     

The settlement of power sales within Tamil Nadu by wind and solar energy generators connected to the intra-state transmission network will be determined based on the actual generation.

Deviation settlement will be the responsibility of the respective generators. Generators are obligated to pay provisional deviation charges in each monthly bill at the capped price for the total generated units during the billing month.

The final settlement at the end of the financial year will be conducted as outlined below.

Regarding the sale or self-consumption of power within Tamil Nadu, if the actual injected generation of wind or solar power varies from the scheduled generation, the generator is required to pay the deviation charge for the excess or shortfall to the “State Deviation Pool Account (Wind and Solar)” through the SLDC.

The total deviation charges deposited due to deviations by wind/solar generators into the state deviation pool account (wind and solar) in a financial year will be capped at the ceiling rate of ₹0.03 (~$0.00036)paise/kWh multiplied by the total annual generation at the respective pooling sub-stations/total generated units in statewide aggregation.

Any deviation charges beyond the capped amount, as per the deviation account statement over the financial year, will be adjusted in the subsequent billing without interest.

Deviations resulting from the forced shutdown of a generating plant due to abnormal weather conditions such as cyclones, heavy rainfall, floods, or gusty winds, if communicated by the QCA to the SLDC well before six hours of occurrence, will be excluded from the scope of deviation charges upon verification by the SLDC.

Deviation Settlement for Inter-State Transactions

The sale of power outside Tamil Nadu by generators connected to the intra-state transmission system or distribution system will be settled by the procurers. The QCA/generators are not permitted to aggregate their inter-state transaction schedule with intra-state transactions.

Inter-state transactions at a pooling substation will be allowed only if the generator concerned is connected through a separate feeder/metering arrangement. A generator intending to engage in inter-state transactions must submit a separate schedule for its energy generation, following these regulations, to the SLDC and the concerned regional load dispatch center (RLDC) through the QCA.

The SLDC will prepare the deviation settlement account for such QCA based on the measurement of the deviation in the energy injected. Deviation charges for over/under-injection by generators connected to the intra-state transmission network and selling power outside Tamil Nadu will be as per the Central Electricity Regulatory Commission (Deviation Settlement Mechanism and Related Matters) Regulations, 2022.

Deviation Settlement for Inter and Intra-State Transactions;

Deviation handling for inter-state and intra-state transactions concerning each source of renewable energy will be managed separately at each pooling sub-station or the state level.

The SLDC will calculate deviations by comparing scheduled generation with the actual generation, determining deviation charges payable by the generators, and issuing monthly bills for intra-state transactions.

For inter-state transactions, the SLDC will compute deviations based on scheduled and actual generation, establishing deviation charges payable/receivable.

The SLDC will provide separate energy and deviation accounts for inter-state and intra-state transactions concerning wind and solar generation to the respective QCA, which is responsible for settling deviation charges with the concerned generators.


Each pooling sub-station/generator is required to have an energy meter with the capability to record energy in specified time blocks as per the Central Electricity Authority (CEA) Regulations governing metering. The meters must be time-synchronized through commands from the centralized, automated meter reading system.

Data from existing metering arrangements at SLDC will be shared with QCAs appointed by generators. QCAs are responsible for capturing, transferring, and analyzing shared data without disrupting their systems. QCAs must develop a web portal that provides stakeholders access to real-time schedules versus actual generation details.

The SLDC will provide real-time data for forecasting activities upon the QCAs’ request, and any forecasting errors will be attributed to the QCAs. In case of system inoperability, the relevant licensee shall provide 15-minute time block data to the SLDC within three working days for charge calculation.

Generation meters’ health should be maintained, and defective meters should be replaced within 30 days; otherwise, the licensee will replace the meter with charges adjusted in the generator’s monthly bill.

For hybrid systems, separate metering arrangements for wind and solar generation are required, with deviations considered independently. The metering system should adhere to the CEA (Installation and Operation of Meters) Regulations, 2006, and subsequent amendments.

Deviation Accounting

Deviation settlement methodology for the state involves SLDC computing the absolute error (difference between actual and scheduled generation) for statewide aggregation, each pooling sub-station, or each generator. The SLDC will determine amounts payable/receivable for the deviation charge.

  • SLDC will compute the deviation charges for the state as a whole at the state periphery.
  • SLDC will compute the impact of wind and solar energy generation deviations and their contribution to the deviation charge at the state periphery, maintaining the state deviation pool account separately for intra-state and inter-state transactions.

Payment Mechanism for Deviation Settlement and Payment Security

Every generator must remit the total deviation charges for the respective months to the SLDC on a statewide aggregation/PSS-wise/Generator-wise basis, as outlined in Regulation 7.

Generators should make provisional payments towards deviation charges based on the ceiling amount specified in Regulation 7.2 for each unit of generation monthly, using actual generation data obtained through AMR/CMRI readings. Deviation charges can be paid to the SLDC through the Distribution Licensee from the Generator’s monthly bill.

Delayed payments of deviation charges will incur a simple interest of 0.06% for each day of delay. Any excess or shortfall in the deviation charges will be reconciled annually, with SLDC handling the collection, refund, or adjustment to generators through the distribution licensee within 60 days after the financial year ends. In case of delays beyond 12 days from the deviation charge statement issue, payments to QCAs/generators can be made from the available balance in the State Deviation Pool Account (Wind and Solar).

Intimation of Curtailment

SLDC will communicate to the QCA any curtailment imposed on energy injection for reliable and secure grid operation in emergent situations. No deviation charges shall be payable for such curtailment.

In case of planned curtailment communicated by SLDC due to line maintenance or other reasons, the QCA is responsible for informing generators to curtail generation at the site and amending the schedule. Failure to do so will lead to SLDC revising the schedule as required.

The Commission will issue a detailed procedure for the management of curtailment for wind and solar generation within 60 days from the date these regulations are issued.

Energy Accounting

Energy accounting will be based on data recorded by the interface meters.

Respective QCAs will prepare monthly accounts of deviations within pooling sub-stations/statewide aggregation based on SLDC inputs, accessible through an IT-enabled system and software.

SLDC will provide processed data monthly to the concerned QCA in a prescribed format for the preparation of monthly energy accounts from the pooling sub-station/generators.

SLDC should promptly correct any communicated discrepancy by the QCA within 15 days after verification.

The SLDC and distribution licensee will, as mutually agreed, prepare the statement of accounting of energy in each (15-minute) time block for wind and solar energy generators and procurers on a monthly basis for billing purposes. The SLDC is responsible for sharing block-wise generation data with the distribution licensee.

Power to Amend/Remove Difficulties/Relax

The Commission reserves the authority to vary, modify, or amend any provision of these regulations at its discretion.

If implementing the provisions of these regulations is difficult, the Commission may, through a general or specific order, make necessary provisions consistent with the act to overcome the difficulty.

The Commission, by a general or special order and after providing an opportunity for a hearing, may relax any provision of these regulations on its motion or upon an application by an interested person.

The TNERC reduced the rooftop solar network charges for all micro, small, and medium enterprises by 50% from ₹1.53 (~$0.018)/kWh to ₹0.765 (~$$0.009)/kWh.

In February last year, CERC issued new guidelines to supplement the Deviation Settlement Mechanism Regulations 2022 to maintain grid security. The Commission has added a new category of wind-solar generators and introduced charges for DSM.

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