Most open access ground mounts are laid out before anyone reads the state’s STU connectivity procedure. That order is risky. In the procedures read for this guide, the State Transmission Utility (STU) confirms the substation and sets the line voltage. The data it wants arrives in stages. A layout that ignores both gets redrawn.
This guide is for the EPC or developer on a 5 to 50 MW open access ground mount. It picks up where our STU vs CTU transmission planning guide stops, at the STU’s application desk. It lists what each state document asks for, with its title and date. It also says plainly where we could not read the text.
Quick answer. STU connectivity is the usual route for a standalone 5 to 50 MW open access solar plant. The CERC 2022 regulations give individual plants a direct inter-state route only from 50 MW. Each state sets its own package: a signed form, fee proof, authority papers, offtake or land evidence, then models, a single line diagram and agreements. Read your state’s current procedure before fixing the evacuation design.
Does a 5 to 50 MW open access plant connect through the CTU or the STU?
The CERC Connectivity and General Network Access Regulations, 2022 decide who may apply to the Central Transmission Utility of India Limited (CTUIL). They were notified on 7 June 2022, and the copy read is consolidated through the Third Amendment. Regulation 4 lists the applicants. Three clauses matter for a single ground mount.
| Regulation | Applicant that may go to the CTU | Effect on a 5 to 50 MW plant |
|---|---|---|
| 4.1(a) | A generating station, including a renewable one, with or without storage: 50 MW and above, alone or through a Lead Generator that aggregates to 50 MW | A 30 MW plant on its own has no direct route. Aggregation to 50 MW is the way in |
| 4.1(e) | A renewable plant of 5 MW or more that connects through the electrical system of a generating station already holding inter-state connectivity | Possible only with a signed agreement to share that system and its dedicated lines |
| 4.3 | A station already connected, or intending to connect, to an intra-state system | It may also apply to the CTU. That does not remove the intra-state option |
A renewable park developer needs 50 MW under 4.1(d), and 4.1(f) sets a 25 MW minimum in the North Eastern Region and Sikkim. So the practical route for a lone 5 to 50 MW plant is intra-state, unless you aggregate or share a lead generator’s system.
Maharashtra shows the other side. Its Transmission Open Access Regulations, 2016 make a generating station of 5 MW or more eligible for intra-state connectivity in Regulation 5.1. A smaller station may also connect if it is technically feasible. The Internet Archive copy of the Maharashtra Electricity Regulatory Commission (MERC) text is the base version, so check for later amendments.
How do the STU and CTU application packages compare?
The CTU route is one national regulation plus one CTUIL procedure. The STU route is a stack: a state grid code, state open access regulations and an STU procedure approved by the state commission. The table shows what is documented in each. Gujarat entries come from the 2023 procedure discussed below.
| Item | CTU route (CERC 2022) | STU route (examples read) |
|---|---|---|
| Governing text | CERC regulations plus the CTUIL Detailed Procedure dated 10 April 2026 | State grid code, state open access regulations and an STU procedure |
| Application | Online and digitally signed (Reg 3.1) | Gujarat: online portal, then physical copies within a week (para 2.3). Maharashtra: Annexure I form with proof of payment (Reg 5.2, 5.3) |
| Fee | ₹5 lakh plus taxes (Reg 3.2) | Maharashtra base text: ₹1 lakh for renewable generators, ₹2 lakh for others (Reg 5.2) |
| Study | CTU interconnection study under CEA standards (Reg 6.1) | Maharashtra: STU study under CEA standards (Reg 6.1). Gujarat: STU checks margin in the existing and planned network (para 7.1) |
| First answer | In-principle grant in 60 days, or 90 days with augmentation, counted from the last day of the application month (Reg 7.1, 7.2) | Maharashtra: decision within 30 days of a complete application (Reg 6.9). Gujarat: Stage-I grant within 60 days of receipt (para 7.3) |
| Agreement | Connectivity Agreement within 30 days of final grant (Reg 10.1) | Maharashtra: tripartite connection agreement (Reg 6.4) |
The CTU route also carries bank guarantees (BG). Conn-BG1 is ₹50 lakh, Conn-BG2 is set per terminal bay by voltage, and Conn-BG3 is ₹2 lakh per MW (Regulation 8). State BG terms differ and are not tabulated here.
Which state documents govern STU connectivity?
Four states, four different stages of change. The table lists what we could open and read. Where a source was an archived or third-party copy, the note says so.
| State | Documents read (title and date) | STU | How it is staged |
|---|---|---|---|
| Gujarat | GERC letter approving the Procedure for Grant of Connectivity to Projects based on Renewable Sources to Intra-State Transmission System, dated 7 January 2023 (first pages only, from a copy of the GERC letter). The GETCO renewable integration page (Internet Archive, 29 November 2025) lists a newer approved procedure dated 4 August 2025 | GETCO | Stage-I, then Stage-II |
| Maharashtra | MERC Transmission Open Access Regulations, 2016 (base text). MSETCL’s revised RE Grid Connectivity Procedure dated 7 January 2025, as quoted in MERC Order in Case No. 143 of 2024 (23 June 2025) | MSETCL | Grant of connectivity, then a tripartite connection agreement |
| Rajasthan | RERC regulations index (Internet Archive, 15 October 2026) lists the Rajasthan Electricity Grid Code Regulations, 2024, dated 29 January 2025. RVPN’s draft procedure, issued under Regulation 17 of that code, is a draft with no date printed on it | RVPN | Stage-I, Stage-II, Stage-III |
| Karnataka | Karnataka Electricity Grid Code Regulations, 2025 (21 July 2025), as cited in the KPTCL circular of 15 June 2026 that issues the first-time charging procedure KERC approved on 21 May 2026 | KPTCL | Connectivity-grant text not read. Charging stage only |
Gujarat’s 2023 procedure is therefore a structural guide, not the current rulebook. The GETCO page calls the 7 January 2023 procedure the earlier one, and it says new renewable connectivity applications go through the Akshay Urja Setu portal. We could not open the 2025 text, so nothing below claims what it contains. The Rajasthan draft is used the same way. It shows the kind of documents RVPN proposed, and the approved text may differ. Karnataka appears for its charging-stage data, because the connectivity-grant text was out of reach. We did not read procedures for other states.
What is in each state’s STU connectivity package?
This is the matrix. “Not in text read” means the document we opened does not say, not that the requirement is absent. Section numbers refer to the sources above.
| Document | CTU (CERC 2022) | Gujarat (2023) | Maharashtra (2016 base text) | Rajasthan (RVPN draft) | Karnataka (KPTCL 2026) |
|---|---|---|---|---|---|
| Signed form and fee proof | Online form, ₹5 lakh (3.1, 3.2, 5.8) | Format-2 form, fee per state open access regulations (6.1, 6.2) | Annexure I form, ₹1 lakh for renewable (5.2, 5.3) | Annexure-1 or 2 with fee table (4) | Not in text read |
| Authority papers | Board resolution, CEA Registry certificate (5.8) | Notarized affidavit, board resolution, constitutional documents (6.2) | Form lists enclosures generally | Board resolution or authorization letter (4) | CEA registration at charging stage |
| Location and capacity | Location, installed capacity, preferred point of connection (5.8) | Substation picked from GETCO’s monthly list (6.1) | Address, capacity, technology, generation and step-up voltage, commissioning schedule (Annexure I) | Location, quantum, substation name, voltage, timeline. RREC registration first (4) | Not in text read |
| Offtake and land evidence | Separate document lists for LOA or PPA, land, and land BG routes | Stage-II: LOA, LOI or PPA, tentative land location or map, BG (8.2.1) | Not in text read | Stage-II: LOA, PPA or PSA unless captive, RREC approval (4) | Not in text read |
| Plant and machine data | Generator data for fault studies and dynamic simulation, one year before physical connection (10.1) | Not in pages read | Not in text read | Machine data, Annexure-5, with the application (4) | Static and dynamic modelling data, six months before charging |
| Models and study reports | Steady state, dynamic and power quality models and reports (CTUIL procedure) | STU runs the feasibility study (7.1) | STU runs the interconnection study (6.1) | Models and studies before physical interconnection (8) | Included in the data above |
| Single line diagram | CTU supplies the SLD of its substation with the final grant (9.1) | Not in pages read | Not in text read | Plant and pooling station SLD approved by the STU (connection agreement 1.4). CEIG-approved SLD in the charging list (Annexure-10) | Annexure A3: substation SLD with bay and bus status |
| Bay and dedicated line | CTU names the terminal bay and minimum line design features (7.1) | STU sets line voltage (7.4). No bay rights with Stage-I (7.3) | STU states switchyard and interconnection design up to the injection point (6.2) | Applicant builds the line to the point of connection (8, 10.1). Bay charge or BG (5) | Not in text read |
| Line route approvals | Not in text read | Not in pages read | Not in text read | Charging list (Annexure-10): forest approval with NOC, PTCC route approval, Section 68 permission, Section 164 right of way | Not in text read |
| Agreement | Connectivity Agreement within 30 days of final grant (10.1) | Connectivity agreement referred to (2.2). Format not read | Tripartite connection agreement (6.4) | Stage-III connection agreement (4) | Annexure A6: agreement and site responsibility schedule |
Two readings stand out. First, the single line diagram sits at different points. The CTU supplies its own. Rajasthan’s draft wants the plant diagram approved by the STU and later by CEIG. Karnataka wants substation diagrams with the charging request. Second, line route approvals appear only in the Rajasthan charging list. That is a project-schedule item to confirm in your state, not a footnote.
Which studies does a solar STU connectivity file need?
In the texts above, the STU or CTU runs the interconnection study. The applicant supplies data and models. The study names that the sources use are these.
- CTUIL: simulation models and reports covering steady state, dynamic and power quality, submitted at least one year before physical connection. A connection-details application without them is treated as incomplete and closed after 15 days.
- CERC Regulation 10.1: generator data for fault studies and dynamic simulation data, also one year before physical connection.
- RVPN draft: the plant submits its model and studies, then corrects any gap against the CEA Technical Standards for Connectivity before interconnection. The charging list asks for a PSS/E demonstration of low and high voltage ride-through (LVRT and HVRT). It also asks for static and dynamic inverter data, a simulation report and harmonics test reports.
- KPTCL procedure: static and dynamic modelling data six months before expected first energization, under Clause 4.6 of the Karnataka grid code.
Load flow and short circuit are the usual engineering names for the steady-state and fault studies in that list. That mapping is our reading, not the wording of any one regulation. The RVPN draft adds a useful input: the plant breaker must interrupt at least the short circuit current advised by the STU. You need that figure from the STU before you can size the breaker. Our relay coordination study guide covers the protection side.
Which drawings should the connectivity package carry?
None of the sources hands you a drawing list. The set below is our recommended package, mapped to the source items that support each drawing. Treat the mapping as a starting checklist and confirm it against the current procedure.
- Grid-connected single line diagram, plant and pooling station through to the point of connection. Backed by the Rajasthan draft (STU approval) and Karnataka Annexure A3. Our single line diagram reading guide shows the conventions.
- Bay interface sketch at the STU substation. In the documents read, the bay belongs to the STU or transmission licensee. The Rajasthan draft treats later bay additions as deposit work done by RVPN. Your drawing records the line gantry, isolator with earthing switch on the generator side, and metering points. It is an interface, not the bay design.
- Line route plan and profile from the plant boundary to the substation. It feeds the forest, PTCC route and right-of-way items in the Rajasthan charging list, and it fixes the line length for the study data.
- Protection and metering scheme. Rajasthan’s draft caps primary protection fault clearance at 100 milliseconds for equipment at 132 kV and above. It also lists a no-volt relay interlock and check synchronizing relays. Karnataka asks for the SCADA point list (Annexure A4) and meter types and locations (A5).
- Study reports and model files, in the formats the STU or CTU publishes.
Heaven Designs prepares ground mount engineering design packages that include DC and AC electrical layouts and single line diagrams. The STU decides the substation, voltage and bay, and the state authority decides connectivity. For the substation side of the same plant, see our substation layout and earthing guide.
What do the bay and line design inputs look like?
Two documents give voltage-to-capacity tables, and they measure different things. Gujarat’s 2023 procedure sets the minimum power carrying capacity per circuit of the dedicated line, unless the Stage-I grant says otherwise. The Rajasthan draft sets the maximum injection used to compute connectivity charges at each voltage.
| Voltage | Gujarat 2023: minimum dedicated line capacity per circuit (MW) | Rajasthan draft: maximum injection for connectivity charges (MW) |
|---|---|---|
| 33 kV | Not listed | 15 |
| 66 kV | 50 | Not listed |
| 132 kV | 80 | 50 |
| 220 kV | 300 | 132 |
| 400 kV | 900 | 515 |
Here is an illustrative case with assumed numbers. A 40 MW AC plant sits within the 50 MW minimum capacity of a 66 kV circuit in the Gujarat table. In the Rajasthan draft table it exceeds the 15 MW listed for 33 kV and falls within the 50 MW listed for 132 kV. The same plant could therefore reach different voltages in different states, and in Gujarat the STU indicates the voltage at Stage-I (para 7.4). Do not price the line until that letter arrives.
The Rajasthan draft charges ₹2.5 lakh per MW or the actual bay cost, whichever is higher, and asks for a BG equal to the bay cost. It is a draft figure. Check the approved text.
Collect these design inputs from the STU letter: substation name, bay location, line voltage, short circuit level at the point of connection, and the connection agreement format. Put the question of who builds the line and obtains the permits into the EPC contract technical specification before the contract is signed.
Which timelines can you cite?
Only the ones below come from the documents read. Each clock starts when the application is complete, so the real date depends on how clean your package is.
| Step | Time limit | Source |
|---|---|---|
| CTU in-principle grant, no augmentation | 60 days from the last day of the application month | CERC Reg 7.1 |
| CTU in-principle grant, with augmentation | 90 days from the last day of the application month | CERC Reg 7.2 |
| CTU Connectivity Agreement | 30 days from final grant | CERC Reg 10.1 |
| CTU technical connection data | At least one year before physical connection | CERC Reg 10.1 |
| Maharashtra decision on connectivity | 30 days from a complete application | MERC TOA Reg 6.9 |
| Gujarat Stage-I grant (2023 text) | 60 days from receipt | Para 7.3 |
| Gujarat Stage-II application (2023 text) | Within six months of Stage-I, or until the substation is booked, whichever is earlier | Para 6.4 |
| Rajasthan draft: connectivity offer | 60 days from the last day of the application month | Draft 4(i) |
| Rajasthan draft: fix shortcomings | 30 days, notified once | Draft 4(j) |
| Rajasthan draft: use of the evacuation approval | Three years from approval | Draft 8(c) |
| Karnataka: modelling data | Six months before expected first energization | KPTCL procedure |
| Karnataka: notice before charging | Ten working days | KPTCL procedure |
What is still moving in these states?
Verify each of these before you rely on a row of the matrix.
- Gujarat: the GETCO page lists an approved procedure dated 4 August 2025 and routes new applications through the Akshay Urja Setu portal. The 2023 content in this guide may no longer apply to a new application.
- Maharashtra: MSETCL issued its revised procedure on 7 January 2025. In its June 2025 order the commission recorded that the procedure lets a hybrid project apply for the higher of its wind or solar capacity. The 2016 regulations in our copy may have been amended since.
- Rajasthan: the RVPN text we read is a draft. Find the approved procedure on RVPN or RERC before you copy any figure.
- Karnataka: the grid code is dated 21 July 2025 and the charging procedure was approved on 21 May 2026. We did not read a connectivity-grant procedure.
Where does open access start?
Connectivity is a right to connect. It is not a right to sell. MERC Regulation 6.5 says a grant of connectivity does not by itself entitle the applicant to interchange power through open access. The Rajasthan draft says the same. Open access approvals, charges and scheduling follow later. Our state guide to solar open access covers that stage. If you are repowering an operating plant, existing connected capacity does not reapply, but added capacity does. Both Gujarat’s procedure and Maharashtra’s Regulation 6.9 say so, and our repowering guide shows how that interacts with the AC limit.
FAQ
Can a 40 MW plant apply to the CTU directly?
Not on its own under Regulation 4.1(a), which starts at 50 MW. It can aggregate to 50 MW through a Lead Generator, or share the electrical system of a station that already holds inter-state connectivity under 4.1(e). Otherwise the intra-state route applies. See the CTU and STU glossary entry for the roles.
Does STU connectivity let me sell power through open access?
No. In both MERC Regulation 6.5 and the Rajasthan draft, connectivity is separate from open access. You still need the open access approvals. Our open access glossary entry defines the terms.
Who builds the dedicated line to the substation?
In the Rajasthan draft, the applicant builds the line up to the point of connection, whatever the connectivity quantum. Maharashtra’s Regulation 5.1 treats a connecting feeder above 33 kV as part of the transmission lines under Section 2(72) of the Electricity Act. Confirm ownership and permit responsibility with your STU.
Is the Gujarat 2023 procedure still the one to follow?
Treat it as superseded until you have checked. The GETCO page we read lists a procedure approved on 4 August 2025 and labels the 2023 procedure as the earlier one. The state regulator, GERC, approves those procedures.
Where do the CEA connectivity standards fit?
They sit under all of this. MERC Regulation 6.1 and CERC Regulation 6.1 both point the interconnection study to the CEA Technical Standards for Connectivity. Our CEA connectivity regulations guide and the CEA connectivity glossary entry cover the technical layer. For high-voltage design, see the HV interconnection guide.
Next step
Pull your state’s current STU procedure and compare it with the matrix before you freeze the layout. Then list the drawings the STU letter will need. If your 5 to 50 MW ground mount needs the electrical and civil package behind that application, see our ground mount design service. You can also write to us through the contact page. Scope and turnaround are agreed at scoping, and the utility and the state commission make the connectivity decision.