Written for a first-time reader: what each term means in the filings, and what it means when this site uses it. A reference — start anywhere.
Who runs the grid, and who decides who connects to it.
Inter-State Transmission System: the high-voltage national network power crosses when it moves between states. A generator in Rajasthan selling to a buyer in Maharashtra is on the ISTS. Connecting to it is permission-based, and that permission is the entire subject of this platform.
Central Transmission Utility — the body that operates the inter-state grid and, critically for us, grants connectivity. As a company it is CTUIL (Central Transmission Utility of India Limited). Its filings — margins, grants, queues — are the platform's primary source.
Central Electricity Authority, the technical regulator for the power system. We use its under-construction register: the independent record of which projects are actually being built, matched against what developers hold in the queue.
State Transmission Utility — the CTU's counterpart inside a state. States publish their own draw forecasts (the STU one-pagers we track), which is how the consumption side of the ledger becomes visible.
The grid is operated as five regions — Northern, Western, Southern, Eastern, North-Eastern. Filings tag every substation with one; the map and region views follow these boundaries.
Renewable-energy substations (where solar and wind connect — the headroom book's subject) versus thermal hosts (generation stations with their own switchyards; we carry them for context only, since they take no new renewable connections).
How a project gets permission to connect — the vocabulary of the queue.
General Network Access: the current framework for ISTS connectivity. Instead of asking for a specific line, an applicant asks for a defined amount of access at a named substation, for generation or for consumption. When this site says 'connectivity', it means GNA unless a page says otherwise.
A request for GNA, filed with the CTU. The 4.x register we ingest lists over 1,400 of them with applicant, substation and MW. Each carries an application ID — the number printed on CTUIL letters, which the platform resolves into a full lifecycle view.
Approval in principle: a defined MW at a defined substation is yours — subject to conditions, and to an effectivity date. The granted book across all developers is the platform's core ledger.
The date a grant becomes real. Between grant and effectivity sit milestones: bays, transmission schemes, construction. These dates move — often repeatedly — and the platform's vintage archive exists to measure exactly how much.
Applications still under process at a substation, published as a count and total MW. The register does not publish order — so positions cannot honestly be ranked, and this site never displays one. The queue matters because at many nodes it already exceeds the remaining margin.
Letter of Award — the document that makes a project real after a competitive auction (SECI, NTPC, state auctions). One pillar of the upcoming projects tracker: LoA first, then connectivity, then construction.
Connectivity withdrawn for missed milestones. Revocation lists are published regularly; we track them across editions because revoked MW sometimes returns to the margin — capacity that may come back.
Special-purpose vehicle: the single-project company that almost every application is filed under. One developer group can appear as dozens of SPVs with different spellings; our registry resolves them so the queue reads by who actually holds it.
The corporate entity behind the SPVs — 256 verified groups, from Adani and NTPC to single-project firms. 'Book' on this site means a group's total granted MW across all its substations.
What is being counted at a substation, and the rules we never break.
Remaining connection capacity at a substation. The published book states it separately for solar hours and non-solar hours — two physically different quantities. They are never summed into one number here; any view that needs both shows both.
The grid splits the day by sunlight: roughly, when solar generation is possible versus not. Margin available in the day is not the margin available at night. A solar farm cares about the first; storage or round-the-clock buyers care about the second.
A physical connection slot at a substation — where a line actually terminates. A node can have MW headroom and zero free bays at the same time; without a bay there is no independent new connection, margins notwithstanding. Bays are counted separately at 220 kV and 400 kV.
Margin after the published adjustments — what is genuinely left, not the gross figure. Negative or zero on either hour axis means the node is full on that axis.
Approved grants with future effectivity dates at a node: capacity already promised, scheduled to arrive. Adding dated inflow to the queue gives the ceiling side of a closure bracket.
Herfindahl–Hirschman Index over one developer's book: 0 means perfectly spread across many nodes, 1 means the entire book sits at a single substation. A large book with a high HHI is execution risk — one closure event takes the most with it.
How far an effectivity date moved between two editions of the same register. Median slippage across the archive runs in months, not days — which is why every dated forecast on this platform is drawn as a bracket.
The documents themselves — what each one is, in filing language.
One publication of a register. Registers re-issue monthly or quarterly; comparing consecutive editions of the same register is how date moves, departures and growth become observable at all.
The headroom book: solar and non-solar margins per substation, published with the GNA regulations. Currently a single edition — until a second exists, erosion rates are honestly marked not computable.
Per-application and per-node annexures: grant status and bays granted (B); state, allocated bays, queue and net margin per node (C). The bridge from grant-level to substation-level views.
The CTUIL application registers: 4.x lists connectivity applications (generation side), 20.x lists GNA applications (consumption side). The numbering is the filings' own.
The consumption-side granted book for non-STU draw — green hydrogen, bulk industrial consumers, ports. Tracked across editions as the demand side of the ledger.
The effective-grants list: everything approved and awaiting effectivity, with dates. Its vintage archive is the slippage calibration behind every bracket this platform draws.
Vocabulary this platform coined for quantities the filings state only implicitly.
The closure read for a pressured node. The floor: queue alone already covers the margin — closed regardless of any dates. The ceiling: queue plus every dated inflow — closed if stated dates hold. Both edges are drawn because the truth lives between them and dates slip.
The latest month an application could complete ahead of a node's dated closure: measured filed-to-grant latency (a 176-day median, from the archive) subtracted from the crossing year. A bracket, not a promise — but it converts 'closing 2027' into 'file by July 2026, or go elsewhere'.
A node where generation-side claims and consumption-side draw (green hydrogen, bulk users) compete for the same shrinking margin. Six GW sat at such crossings at the last edition — a contest no public page joins, which is why it has a name here.
A substation with a queue, a dated grant, or both against its margin — the 75 nodes the depletion views track. Not the same as full: pressured means the race is on.
Whether the holder of a queue position is actually building, from the CEA under-construction join. A position held by a project under construction and one held by a paper SPV are different facts, and the platform treats them differently.
How fast a node's margin is actually shrinking, edition over edition. Blocked on a second edition of the headroom book; the day it publishes, this becomes computable — and it will be the most valuable number here.