20 MW solar farm electrical design.

Project overview

ASTCAD provided electrical design services for a 20 MW utility-scale solar farm in SE Queensland. Scope covered DC array layout, AC reticulation, inverter stations, HV transformer connections, the substation switchboard and the SCADA integration to the network operator’s monitoring system.

The challenge

The site straddled two soil types with different geotechnical conditions affecting pile depth. The network operator (Energex) required compliance with their specific generator-connection technical standard, and the project had to be deliverable for grid connection within a 14-month programme.

Our approach

• DC array string design optimised for inverter MPPT range
• AC reticulation with VSD-rated cable sizing
• HV transformer and switchgear design for grid connection
• SCADA integration architecture and protocol mapping
• Compliance documentation per Energex connection standard

Deliverables

• DC and AC single-line diagrams
• Array layout drawings
• Inverter station design
• HV substation drawings
• Grid connection compliance package

Outcome

The farm achieved grid connection on schedule. Energy generation has been within 2% of PVsyst-modelled values across the first year of operation. The asset owner has engaged ASTCAD for design support on a 35 MW expansion adjacent to the existing site.

How we approach solar farm electrical design

Solar farm electrical design spans three voltage domains — DC strings, LV inverter output and MV reticulation — and the drawings have to keep them coherent. We produce string and combiner layouts matched to the racking design, size DC cabling for voltage drop and fault conditions, and document inverter station layouts with clearances for service access. MV reticulation design covers ring or radial topology, cable selection with soil thermal resistivity applied, and protection coordination back to the connection point. Earthing design across a large site area is modelled rather than ruled-of-thumb, because step and touch voltages at the fence line are a compliance item, not a detail.

Solar farm drawing set and studies

Typical deliverables include overall site single line diagrams, string wiring diagrams, inverter and transformer station layouts, MV reticulation layout and sections, earthing layout, cable schedules with derating calculations, and protection setting schedules. We coordinate with the civil design for trenching and access roads, and structure the set so the connection application, construction tender and commissioning team can each pull what they need without re-drafting.

Grid connection and compliance workflow

A solar farm electrical design is only as good as its connection approval. We prepare the technical documentation the network operator requires — single line diagrams, protection philosophy, inverter compliance certificates and power quality data — and respond to technical queries through the assessment process. Anti-islanding, voltage regulation and ramp-rate requirements are designed in from the start rather than retrofitted after a connection offer, and the protection settings we publish align with the operator’s requirements at the connection point. This workflow discipline is the difference between a project that energises on schedule and one that sits complete but disconnected while paperwork catches up.

Whether your project is a 5 MW community installation or a utility-scale farm, the electrical design package scales the same way: settled demand and generation figures first, coordinated reticulation and protection design second, connection documentation third. We work alongside your civil designer and EPC contractor so the electrical drawings match what is actually being built on the ground.