13/09/2025
1. Solar Panels (DC Generation)
• Sunlight strikes the solar PV modules.
• Each module produces DC electricity (around 30–50V per panel, depending on type).
• Modules are connected in series (strings) to increase voltage.
• Multiple strings are connected in parallel for current addition.
2. String Combiner Box (SCB) / DCDB
• All strings terminate into DC Distribution Boxes (DCDBs) or String Combiner Boxes (SCBs).
• Each string is fused for safety.
• Surge protection devices (SPD) protect from lightning/surges.
• Outputs combine into a single positive & negative busbar.
3. Inverter (DC → AC Conversion)
• The inverter converts the combined DC into AC power.
• For MW-scale, usually central inverters (500kW, 1MW, 2.5MW, etc.) or large string inverters are used.
• Output is low/medium voltage AC (generally 400V–690V, 3-phase).
⸻
4. AC Combiner / ACDB (Low Voltage Side)
• Output from inverters goes to AC Distribution Board (ACDB).
• Combines all inverter outputs.
• Circuit breakers, MCCBs, isolators, surge protection installed here.
⸻
5. Step-Up Transformer (LV to MV/HT)
• Inverter output (400V/690V) is stepped up to 11kV / 22kV / 33kV depending on DISCOM/grid requirement.
• Transformers may be inverter-wise (unit transformers) or common pool transformers.
⸻
6. HT Panel / Switchgear
• After transformers, the power flows to HT Panel (RMU, VCB, SF6 breaker).
• Protection relays (overcurrent, earth fault, differential) installed here.
• Allows safe switching, isolation & grid synchronization.
⸻
7. Main Pooling Switchyard (within plant)
• All transformer outputs are collected at the main pooling point/switchyard.
• Plant metering is done here (ABT meters, CT/PT).
• Step-up to required evacuation voltage (usually 33kV).
⸻
8. Transmission Line (Evacuation Line)
• From pooling switchyard, power is evacuated via transmission line (underground or overhead).
• Length depends on distance to DISCOM substation / client substation.
⸻
9. Grid Substation (DISCOM / Client End)
• Solar power is synchronized at the nearest grid substation (33/66/132kV).
• At this point, solar energy is exported to the grid or used internally (captive plant).