What it is and when you need it
Solar plant electrical engineering defines how every part of the plant is connected, from the modules to the point of interconnection with the grid, and puts it into drawings, calculation reports and lists that can be built, inspected and approved. It covers the DC side, the inverters, the AC side, transformation, protection, grounding and control.
You need it at two moments: before requesting the connection, when the grid operator reviews the project, and before construction, when the contractor needs a detailed design that complies with the local electrical code. We do it for industrial and commercial self-generation, for distributed generation and for plants connected to transmission or sub-transmission substations. It is electrical engineering: supply and construction stay with your contractor.
What is included
DC side
- String configuration and its verification against the inverter voltage window at the site temperatures.
- Selection of conductors, fuses, disconnects and surge protection, with the criteria of IEC 62548-1 and your local code.
- Combiner boxes where the architecture uses them, labeling and disconnecting means.
AC side and transformation
- General single-line diagram and one for each board, with breaking capacities and basic coordination.
- Transformer stations, the medium-voltage collector network and step-up substation engineering, when the project has one.
- Connection point to the grid or to the user’s board, per your local code and the operator’s standard.
Protection and control
- The protection scheme of the point of interconnection per your grid code, with its instrument transformers and switching device.
- Control, metering and communications architecture of the plant.
Grounding and lightning
- The grounding system, equipotential bonding of structures and lightning protection.
Documentation
- Drawings and calculation reports for the grid operator and for the inspection body, where your local code requires one.
- Technical specifications of the equipment and electrical bills of materials.
What changes with the size of the plant
| Project | Connection | What weighs most in the engineering |
|---|---|---|
| Small-scale self-generation on a roof or on the ground | The operator’s low- or medium-voltage network | DC side, connection point at the board, import and export metering, and protection of the connection |
| Distributed generation and large-scale self-generation on the distribution grid | The operator’s medium voltage | Transformer station, switching device, point-of-interconnection relay and, where applicable, the simplified interconnection study |
| Plant connected to the transmission or sub-transmission grid | Step-up substation | Collector network, substation, main and backup protection, plant control and supervision by the system operator |
On the distribution grid, many grid codes allow the protection functions of small inverter-based plants to sit in the inverter itself; above a certain size they require at least one protection scheme at the point of interconnection. We apply the threshold of the code that governs your project.
How we work
We do it from our office, with no travel costs, and go to site only when the project requires it.
- Scope. We review the size of the project, the point of interconnection, the type of application and the operator’s technical standard.
- Basis information. Layout, module and inverter datasheets, site data and the feasibility response, if you already have it.
- Basic engineering. Single-line diagram, DC and AC architecture and protection scheme, for the connection application.
- Detailed engineering. Calculations, drawings, specifications and lists, ready to build.
- Review and approval. We address the comments of the grid operator, the inspection body and the contractor until each one is closed.
Standards and criteria in solar plant engineering
The installation must comply with the electrical code in force where the plant is built, which treats modules, inverters, cables, surge protective devices and batteries as products with their own requirements and refers to the installation code for the installation itself. IEC 62548-1 serves as the reference for the design of the photovoltaic array, and IEC 60364-7-712 for photovoltaic installations. Conformity is shown with product certificates, the declaration of compliance and, where applicable, an inspection report.
The connection is governed by your country’s interconnection rules for self-generation, distributed generation and large plants, and the protection of the point of interconnection by the grid code and utility requirements. IEEE 1547 can serve as a technical reference. When the connection needs studies, we carry them out with the same model: see grid interconnection studies and interconnection feasibility.
What you receive
- A single-line diagram and electrical drawings for the DC and AC sides.
- Calculation reports for strings, conductors, protection and grounding.
- The protection scheme of the point of interconnection.
- Technical specifications and electrical bills of materials.
- A documented answer to the comments of the grid operator and the inspection body.
Why Tiza Group
- Engineering with a field mindset: we design what we later test and commission, from the string to the substation.
- Medium, high and extra-high voltage, for industrial self-generation and for plants connected to the grid.
- Remote, wherever the project is.
This service is part of our engineering design and studies. Do you have a solar project under development? Tell us about it and we will propose the scope.