A transformer-connected solar plant is designed from the grid connection backwards: PV strings feed low-voltage inverters, the inverter bus feeds a step-up transformer, and the HT panel, protection relay and meter connect the plant to the utility. By the end, you will be able to match Sungrow inverter capacity with transformer kVA, distinguish suitable model arrangements, verify Maharashtra interconnection requirements and check whether a Pune quotation represents a deliverable unit.
Key takeaways
- A 15 kW SG15RT-P2 needs low-voltage AC equipment before an 11 kV connection.
- Size the transformer for inverter kVA, voltage ratio, vector group and site load.
- Match SG110CX, SG125CX-P2 or SG150CX to plant capacity and grid design.
- Confirm protection settings, earthing documents and Maharashtra utility approval before ordering.
How power flows from PV strings to the Pune utility connection
A 15 kW SG15RT-P2 operates on the low-voltage side; it does not connect directly to Pune’s 11 kV feeder. The plant must carry power through a defined AC and HT equipment chain before reaching the utility connection.
1. Connect PV strings to DC isolators and, where required, string combiner boxes. Route each string through its fuse, surge protection and monitoring before it reaches the inverter.
2. Connect the inverter outputs to an AC combiner or LV switchboard. This board collects multiple inverters, provides MCCBs or ACBs, surge protection and isolation, and feeds the transformer.
3. Select a transformer for the inverter’s actual AC voltage: 0.4/11 kV for many smaller units or approximately 0.8/11 kV for SG110CX and SG150CX arrangements. Solar on grid inverter transformers also require suitable kVA, vector group, neutral treatment, impedance and tap settings.
4. Feed the transformer’s HT output into an 11 kV panel containing the circuit breaker, disconnectors, CTs, VTs and earthing switch. The transformer provides voltage step-up and galvanic separation where its construction and vector group provide it.
5. Install protection relays for overvoltage, undervoltage, overfrequency, underfrequency, earth fault and loss of mains. Coordinate these functions with inverter anti-islanding, LV breakers and transformer protection.
6. Route the protected HT circuit through approved revenue metering, then to the utility-owned isolation point and Pune distribution or transmission connection.
For a sungrow solar inverter for transformer connected projects in pune, show every voltage level, ratio, relay, metering point and earthing arrangement on the single-line diagram before ordering equipment.
How to size the step-up transformer for inverter kW and kVA
A 110 kW inverter does not automatically need a 110 kVA transformer. The transformer must carry the inverter’s maximum apparent power at its actual AC voltage, such as 0.8/11 kV for SG110CX or SG150CX, or 0.4/11 kV for a smaller three-phase inverter.
The term solar on grid inverter transformers covers several designs, so check the electrical duty rather than relying on the label.
1. Convert inverter output to kVA: kVA = kW ÷ power factor. At unity power factor, 110 kW equals 110 kVA; at 0.95 power factor, it requires about 116 kVA. Include the inverter’s stated maximum kVA and reactive-power or voltage-support setpoints, because those can exceed the kW rating.
2. Add the outputs of inverters that can operate simultaneously, then select the next practical transformer rating above that total. Do not count unused AC capacity as spare capacity.
3. Obtain the transformer supplier’s harmonic-loss calculation. Inverter current harmonics create additional winding and stray-flux heating; use a harmonic derating factor or K-rated design when the calculation requires it.
4. Apply the specified ambient-temperature correction and permissible continuous loading. A transformer that meets its nameplate rating in a cooler test environment can overheat at the site’s design temperature when loaded continuously.
Coordinate percentage impedance with the fault-level study and inverter voltage window. Higher impedance limits fault current but increases voltage drop, while vector group, neutral treatment, tap range, insulation level and cooling method affect protection and operating performance.
Choosing SG15RT-P2, SG110CX, SG125CX-P2 or SG150CX
Use one or more SG15RT-P2 units for a small rooftop system, SG110CX or SG125CX-P2 for a distributed commercial plant, and SG150CX for a larger transformer-connected array with fewer inverter stations.
| Option | Best fit | Connection arrangement |
|---|---|---|
| SG15RT-P2 | Small rooftop or fragmented roof areas | 15 kW three-phase inverter on the low-voltage side of a 0.4/11 kV transformer |
| SG110CX | Distributed commercial plant | Approximately 800 V AC output feeding an AC switchboard and a suitably rated 0.8/11 kV transformer |
| SG125CX-P2 | Larger commercial blocks with multiple roof sections | Multiple high-power string inverters grouped before the step-up transformer |
| SG150CX | Larger transformer-connected array | Fewer inverter units, shorter low-voltage collection runs, and an approximately 800 V AC transformer interface |
Do not connect an SG15RT-P2 directly to an 11 kV feeder. Its multiple MPPTs suit separate roof orientations and shading conditions, but many units increase AC combiner, cable, protection and maintenance work.
Compare every option at the plant interconnection point: inverter kW and kVA, DC oversizing, MPPT current limits, clipping, transformer and cable losses, MV switchgear, relay, metering and monitoring. A lower inverter price can lose its advantage after these additions.
For a sungrow sg15rt p2 in pune, confirm the number of units and transformer package. For a sungrow sg110cx supplier in pune or sungrow sg150cx availability in pune, obtain written confirmation of model suffix, manufacturing date, certification, firmware, warranty start, spare fans and commissioning support.
Checking protection, earthing and Maharashtra grid approval
Approval is proved at the interconnection point, not by the inverter datasheet alone. For an 11 kV or higher export, obtain the applicable MSEDCL or MSETCL checklist and design to the CEA Technical Standards for Connectivity to the Grid and CEA safety regulations.
Submit a signed single-line diagram showing:
- PV strings, inverter AC voltage, LV breaker, AC switchboard, transformer ratio and vector group
- Neutral or earthing-transformer arrangement, transformer impedance, tap position and HT panel
- Protection relay functions, metering point and utility-owned isolation point
The protection study must coordinate the inverter, LV breaker, transformer, MV breaker and utility feeder for overvoltage, undervoltage, overfrequency, underfrequency, earth fault, short circuit and loss of mains. An inverter behind a transformer still needs anti-islanding.
Ask the supplier and EPC contractor for these records:
- Inverter type-test and grid-support certificates, protection settings and firmware version
- Transformer routine-test report, vector-group confirmation, impedance, insulation and temperature-rise results
- Relay coordination curves, secondary-injection test report and breaker trip-test record
- Earth-grid resistance measurement, continuity results and neutral-earthing drawings
- Commissioning report witnessed or accepted by the distribution utility
The phrase solar on grid inverter transformers covers dedicated inverter-duty units, packaged skids and conventional transformers. For a Sungrow solar inverter for transformer connected projects in Pune, verify every document against the selected receiving voltage; the SG15RT-P2 remains on the low-voltage side and does not connect directly to 11 kV.
What to verify before ordering a Sungrow inverter in Pune
Compare quotations at the plant interconnection point, not by inverter nameplate price. A Sungrow SG15RT-P2 in Pune may need several units, additional AC combining and a 0.4/11 kV transformer; an SG110CX or SG150CX may use approximately 0.8/11 kV equipment. Include transformer losses, LV cable losses, MV panels, protection relay, monitoring gateway and expected clipping.
Demand these documents and commitments from every seller:
- Exact model suffix, firmware generation, AC-voltage version, manufacturing date and serial-number format.
- Datasheet showing rated kW and kVA, DC oversizing limit, MPPT voltage range, maximum input current and short-circuit current.
- Indian certification documents, warranty terms, warranty-start condition, and written confirmation that the proposed firmware suits the project.
- Single-line diagram showing inverter quantity, AC combiner, transformer, HT panel, metering and protection interfaces.
- Delivery date, dispatch location, installation responsibility, commissioning support, training, replacement procedure and spare-fan availability.
- A priced bill of materials separating inverter, gateway, transformer, cables, protection equipment and civil work.
| Model | Verify before accepting | Cost or risk if missing |
|---|---|---|
| SG15RT-P2 | Unit count, 400 V arrangement and transformer capacity | More combining hardware and losses |
| SG110CX | Suffix, approximately 800 V AC compatibility and certification | Wrong transformer or approval delay |
| SG150CX | 1,100 V DC design, MPPT and current limits, firmware | String mismatch or clipping |
Treat “sungrow sg110cx supplier in pune” and “sungrow sg150cx availability in pune” as leads, not proof of stock. Celestial Renewexperts LLP can be compared fairly only against a quotation carrying these same documents and supply obligations.
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Frequently asked questions
Can a Sungrow SG15RT-P2 connect directly to an 11 kV feeder?
No. The SG15RT-P2 operates on the low-voltage side and requires AC collection, protection and a step-up transformer before the 11 kV utility connection.
How do you size a transformer for a solar inverter project?
Use the inverter’s continuous kVA output, voltage ratio, vector group, impedance, harmonics, ambient conditions and expected operating margin.
Which Sungrow inverter suits a transformer-connected commercial project?
Compare the SG15RT-P2, SG110CX, SG125CX-P2 and SG150CX by output kW and kVA, MPPT design, AC voltage, string layout and the proposed transformer arrangement.
What approvals and protection checks are needed in Maharashtra?
Verify the utility’s interconnection requirements, HT metering and protection scheme, relay settings, isolation points, earthing system and required submission documents before energisation.
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