Industries
Transformers and switchgear for solar, wind and battery storage connections
Step up transformers, medium voltage switchgear and substations for solar, wind and battery storage sites, sized against the grid code rather than the nameplate of the generators.
A generation or storage connection runs the transformer the other way round: it steps the inverter voltage up to the network. The transformer sees the inverters' harmonic profile, and on a battery site it carries power in both directions.
Grid codes commonly require the plant to provide reactive power, which means the connection and the transformer are sized on apparent power rather than on the active power of the generators or batteries. A transformer chosen against the kilowatt rating of the inverters can fall short of what the code requires.
The equipment chain
What decides the ratings
The reactive power capability the grid code requires sets the apparent power the transformer must carry. German medium voltage connection rules, for example, require generating units to provide reactive power between cos φ 0.95 under excited and 0.95 over excited, which puts the apparent power at least at the active power divided by 0.95.
Transformers for photovoltaic and wind applications are not excluded from the EU transformer loss regulation by its exemption for transformers supplying DC loads, which expressly does not cover them.
What to settle early
| Consideration | Why it matters here |
|---|---|
| Reactive power requirement | Sets the apparent power rating |
| Inverter harmonics | Affect transformer specification and losses |
| Bidirectional duty on storage | The transformer imports and exports |
| Connection point and voltage | Set by the network operator |
| Grid code certification | Plant certificates may be required above a size threshold |
| Insulating gas | EU rules restrict fluorinated gas in new distribution switchgear |
The German example
German connection rules set specific thresholds for certification, simplified procedures and the minimum agreed connection power. The German pages set them out with their legal sources.
Equipment for this application
What we need to quote
| 01 | Active power of the plant and the reactive power requirement |
| 02 | Inverter or converter voltage and number of units |
| 03 | Connection voltage and the network operator |
| 04 | Whether the site stores energy, and the import and export duty |
| 05 | Grid code and certification requirements that apply |
| 06 | Programme date for equipment on site |
Related
Send us the requirement
Send the rating, the voltage and the destination, or submit the specification, drawing or nameplate. Anything missing is raised before it reaches a supplier.