CEA proposes major updates to transmission planning norms
The Central Electricity Authority (CEA) has issued a draft Amendment-II to its Manual on Transmission Planning Criteria, 2023, proposing wide-ranging revisions aimed at aligning India’s transmission planning framework with the changing requirements of the power system. Stakeholders can submit comments on the draft by June 8, 2026.
1150 kV AC transmission system
One of the key proposals is the introduction of planning provisions for 1150 kV alternating current (AC) transmission systems for the first time. The draft specifies voltage limits of 1185 kV maximum and 1115 kV minimum under planning margins, along with fault clearance timelines of 100 milliseconds for three-phase faults. It also proposes single-phase reactor sizes ranging from 220 MVar to 300 MVar.
Data centres classified as ‘critical loads’
The draft also classifies data centres as “critical loads” alongside railways, airports, refineries, hospitals, and similar infrastructure. This classification would require 100% redundancy and interconnection from two separate supply sources wherever feasible.
CEA has proposed revised steady-state and emergency voltage limits across transmission levels ranging from 66 kV to 1150 kV. The updated N-1 contingency criteria now explicitly cover outage of a 1150 kV single circuit as well as one pole of a high-voltage direct current (HVDC) bipole system.
Expanded renewable integration models
The amendment significantly expands technical annexures relating to renewable energy integration and grid stability. New generic dynamic models have been proposed for voltage source converter (VSC)-based HVDC systems, wind farms, solar parks, battery energy storage systems (BESS), grid-forming converters, static synchronous compensators (STATCOM), and composite residential and commercial loads.
For wind generation, the draft includes modelling components covering drive train systems, pitch control, and aerodynamics. Grid-forming converter models include both droop-based and virtual synchronous machine-based configurations.
Updated load factors and substation limits
CEA has also revised seasonal and regional load factors covering day peak, evening peak, and night off-peak demand for monsoon, summer, and winter conditions. Capacity factors for wind and solar generation have similarly been updated on a regional and seasonal basis.
The draft further introduces updated short-circuit levels and substation transformation capacity limits. Maximum short-circuit levels now extend to the 1150 kV system with values of 50/63 kVA. Transformation capacity limits for 1150 kV substations have been specified at 12,600 MVA.
In addition, indicative parameters for High Temperature Low Sag (HTLS) conductors have been included for 400 kV, 220 kV, and 132 kV transmission lines.
Relay settings revised
The proposed amendment also revises Zone-3 relay setting calculations by incorporating extreme loading conditions equivalent to 120% of thermal current limits and 0.9 per unit voltage. These provisions have also been extended to the proposed 1150 kV transmission system.
The draft Amendment-II reflects the CEA’s effort to align transmission planning norms with the changing structure of India’s power system. The proposed inclusion of 1150 kV transmission systems, data centres as critical loads, and generic models for grid-forming inverters, BESS, and VSC-based HVDC systems points to a stronger focus on renewable integration, reliability, and future grid requirements.
The featured photograph is for representation only.
