Tamil Nadu Dumps 20 year old Grid Code With New Code To Handle Reality OF Renewable Energy

Tamil Nadu has notified a new electricity grid framework to strengthen the supervision, control and operation of the intra-State power system, with the state regulator issuing the Tamil Nadu Electricity Grid Code 2026.

The regulatory document, released by the Tamil Nadu Electricity Regulatory Commission (TNERC), repeals the earlier 2005 grid code and incorporates provisions from the Indian Electricity Grid Code (IEGC) 2023, while embedding state-specific operational requirements.

According to TNERC, the Grid Code lays down procedures to ensure equitable and efficient handling of day-to-day technical operations in the electricity supply system, accounting for a wide range of normal and abnormal operating conditions.

However, the commission noted that the code cannot anticipate every possible operational scenario. In unforeseen situations, the State Load Despatch Centre (SLDC) and the State Transmission Utility (STU) may be required to take decisive actions to maintain grid stability. Users of the grid are required to extend reasonable cooperation and assistance to facilitate such actions.

Under the new framework, the SLDC is authorised to levy and collect fees and charges from generating companies and licensees engaged in intra-State electricity transmission, as specified by the commission.

Grid Code Review Committee

TNERC will approve the constitution of a Grid Code Review Committee through a separate order upon receiving a proposal from the SLDC, within 30 days of the code’s issuance. The STU is required to inform all users in writing of the names and addresses of the committee’s chairman and members within 15 days of its constitution, as well as any subsequent changes.

Planning Focus on Renewables and Flexibility

The code places emphasis on long-term planning of generation and transmission resources to meet projected demand while complying with reliability standards. It highlights the need for an optimal generation mix with greater integration of environmentally friendly technologies, including flexible resources, energy storage systems for energy shifting, and demand response mechanisms to manage the intermittency and variability of renewable energy sources.

The revised norm held STU be responsible for overall planning of the State Transmission System (STS) and will prepare a rolling transmission system plan covering short-term (up to five years), medium-term (up to 10 years), and long-term (up to 15 years) horizons.

Trial Run Norms for Renewable and Storage Projects

The Grid Code sets out detailed trial run requirements for solar, wind, energy storage systems (ESS), pumped storage projects (PSP), and hybrid generating stations connected to the State Transmission System.

For solar projects, trial runs must be conducted for a minimum capacity of 5 MW. Projects exceeding this capacity may complete trial runs in up to four instalments, each with a minimum capacity of 5 MW. A successful trial run requires power flow and communication signals for at least four cumulative hours between sunrise and sunset in a single day, supported by metering, telemetry, power plant controllers, and protection systems.

If rated capacity cannot be demonstrated due to insufficient solar irradiation, commercial operation date (COD) may be declared, subject to the condition that rated performance is demonstrated within one year of COD.

Wind projects must also conduct trial runs for a minimum capacity of 5 MW, with larger projects allowed to complete trials in batches of at least 5 MW. Hybrid projects must successfully complete trial runs for each constituent source in line with applicable provisions of the Grid Code.

For projects with installed capacity of 50 MW or more, trial runs may be conducted in instalments, with each instalment covering at least 20% of the proposed capacity.

Where generating stations fail to demonstrate rated capacity during trial runs, developers may opt for a repeat trial run or de-rate capacity, subject to a minimum aggregated de-rated capacity of 5 MW.

Certification and Commercial Operation

Wind, solar, ESS and hybrid generating stations are required to submit a certificate—signed by an authorised signatory not below the rank of CMD, CEO or MD—to the SLDC and STU before declaring COD. The certificate must confirm compliance with Central Electricity Authority (CEA) technical standards for connectivity, communication and safety, as well as provisions of the Grid Code.

For renewable generating stations aggregating 5 MW or more, COD will be the date declared after successful trial runs, submission of the required declaration, and fulfilment of other conditions specified in the power purchase agreement.