What documents and engineering single-line diagrams are required to apply for commercial solar net metering under utility guidelines?
Applying for commercial or industrial solar net metering under Bangladesh utility guidelines (regulated by SREDA and implemented by distribution utilities like BPDB, BREB, DPDC, DESCO, WZPDCL, and NESCO) requires a standardized engineering and administrative dossier.
Submissions are processed through the national portal (nem.powerdivision.gov.bd) or directly at the utility's zonal office.
1. Technical Engineering Requirements: Single-Line Diagram (SLD)
The Single-Line Diagram (SLD) is the primary engineering document evaluated by utility distribution engineers. It must be prepared and signed/stamped by an accredited electrical engineer or SREDA/SBOI-empanelled EPC contractor.
Mandatory Elements Required on the SLD:
- Generation & DC Side:
- Solar PV array configuration (module capacity, string count, voltage, and series/parallel grouping).
- DC Isolators/Disconnect switches and DC Surge Protection Devices (SPD).
- DC cabling specifications (cross-sectional area in \text{mm}^2, insulation rating).
- Inverter & Protection System:
- Grid-tied inverter specification (kW rating, brand, model, and efficiency).
- Anti-Islanding Protection: Explicit label and functional block showing automatic shutdown/isolation during grid power failure.
- Total Harmonic Distortion (\text{THD}) filtering and grid synchronization parameters.
- AC Side & Interconnection Point:
- AC Circuit Breakers (MCCB/ACB ratings and breaking capacities in \text{kA}).
- AC Surge Protection Devices (Class II SPDs).
- AC Combiner Box / Busbar arrangement.
- Metering Architecture (Crucial for Utilities):
- Generation Meter: Dedicated meter recording gross solar production (100\% generation).
- Bi-Directional Utility Meter: Positioned at the consumer-utility boundary to record both imported grid units and exported solar surplus.
- Instrument Transformer specs (Current Transformers / Potential Transformers ratios, accuracy class) for High Tension (HT) connections.
- Existing Facility Integration:
- Existing Step-Down Transformer (11\text{ kV} / 0.415\text{ kV} or 33\text{ kV} / 11\text{ kV}) rating (\text{kVA}) and impedance (\%Z).
- Main LT Switchgear / Substation incoming breaker.
- Diesel Generator (DG) Synchronizing / Zero-Export Controller: Clear layout showing PV-Diesel hybrid control to prevent reverse current flow into backup generators during outages.
- Earthing & Grounding:
- Dedicated Earth Pits for DC array, Inverter/AC frame, and Lightning Protection System (LPS) with earth resistance target (<1\,\Omega).
2. Administrative & Legal Documents Checklist
| Document Category | Document Name | Description / Requirement |
|---|---|---|
| Application Form | Official Net Metering Application | Signed SREDA/Utility Annexure-1 form submitted with exact consumer account details. |
| Identity & Land | Property Ownership Proof | Land deed, holding tax receipt, or lease agreement matching the electricity account name. |
| Identity & Legal | Company NID & Trade License | National ID of authorized signee and up-to-date Trade License / Certificate of Incorporation. |
| Utility Records | Electricity Bills & Payment Proof | Paid copies of the last 3–6 months' utility bills showing zero outstanding dues. |
| Capacity Proof | Sanctioned Load Verification | Proof that proposed AC capacity does not exceed 100% of the sanctioned load (under updated guidelines). |
| Industrial Clearances | Environmental & Structural NOC | BEPZA NOC (for EPZ zones), ETP approval (for textile/dyeing), or structural engineer certification for older factory roofs. |
3. Equipment Datasheets & Test Certificates
Utilities require technical validation to ensure power quality and grid safety before granting interconnection:
- Solar Panel Datasheets: Factory test reports, flash test reports, IEC 61215/61730 certification, and linear performance warranty documents.
- Inverter Grid Compliance: IEC 62116 (Anti-Islanding), IEC 61727 (Grid Interface), and IEEE 1547 compliance test certificates.
- Bi-Directional Meter Calibration Report: Testing and accuracy certification from an approved utility testing lab.
- Contractor Credentials: Copy of the EPC contractor's SREDA/SBOI empanelment certificate and Bangladesh Electrical Licensing Board (ELB) license.