EngiMetric
Aerial view of rows of photovoltaic modules at a large solar farm

Stage 5 of 13 / Calculation

Check the electrical design

Check the string voltage window, current, DC and AC voltage drop, breaker selection and bill of materials.

  • Practitioner
  • 13 stages
  • 16 min
  • Solar PV and electrical storage
Development preview Solar PV and Battery: Full Engineering Workbench
Development preview. The calculations on this journey run on existing EngiMetric engines, but the journey text and scope have not completed independent engineering review. The route is excluded from search while it remains a preview.
Professional review required.The engines are implemented and unit-tested in this repository, but the journey copy, defaults and boundary still require review by a licensed engineer before publication. The route remains a noindex preview. Current verification state: Needs engineering review.

After this stage you can

Learning objectives
  • Check cold Voc and hot Vmp against the inverter window.
  • Compute DC and AC voltage drop and choose a larger cable when needed.
  • State the protection and coordination work that this stage does not cover.

The engineering

A string that produces the right energy can still be unbuildable. Cold-weather open-circuit voltage must stay below the inverter and system limit; hot-cell maximum-power voltage must stay above the MPPT minimum. The workbench checks both ends of the temperature range, not just standard test conditions.

Cable sizing is a voltage-drop and ampacity problem. The tool computes resistive drop for the stated length and copper area, compares it with the limit, and suggests the next standard area. Ampacity must still be checked against the installation method and derating factors in the applicable code.

Breakers are selected from standard ratings above the design current. That is a screening selection, not a coordination study. Discrimination, earth-fault protection, DC arc-fault detection, surge protection and labelling remain engineering deliverables outside this model.

Switchgear, inverters and transformers in an industrial electrical room
A yield model stops at the terminals. Cables, breakers, voltage windows and protection start here.

EngiMetric / solar workbench

Your project, computed stage by stage

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Preview screen. Inputs are saved in this browser only. Resource presets and tariffs are illustrative. Failed checks stay visible; a clean summary is not a stamped design.

Inputs and outputs

What this stage owns

You own

  • Module electrical data and temperature coefficients
  • Minimum and maximum cell temperature
  • MPPT window, maximum system voltage and inverter DC current
  • String count, cable lengths, areas and ampacities
  • AC voltage, phases, power factor and standard breaker ratings

You produce

  • Twelve pass/fail constraint checks
  • DC and AC voltage-drop results
  • Selected breaker ratings and a screening bill of materials

Your deliverable for this stage

Capstone evidence

A constraint-check table, cable/drop results and a screening bill of materials with failed checks visible.

Stage assumptions, limits and sources

Provenance

Assumptions

  • Cable resistance is computed from copper resistivity at a single reference temperature.
  • Breaker selection uses the stated standard ratings, not a manufacturer catalogue.
  • The array is a single orientation feeding one MPPT window.

Constraints

  • No protection coordination, fault-current or arc-flash study.
  • No installation-method derating, grouping factor or ambient correction for ampacity.

Limitations

  • No earthing/grounding design, lightning protection or equipotential bonding.
  • No structural, fire, labelling or utility interconnection review.
  • A passing screen is not a code compliance certificate.

Review status

  • Needs engineering review
  • Professional review is required before publication or use as a design basis.

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Stage kind: Calculation / Journey: solar-bess-screening / Stage: electrical-design