90 MW Solar Collector Transformer System

A publicly filed New York solar design illustrates how a large plant can be built from repeatable power blocks: 28 inverter stations, 28 transformers rated 3.75 MVA each, a 34.5 kV collector system and a 115 kV point of interconnection.

The design repeats 28 times

Repetition is valuable only when every block is genuinely interchangeable. Cable orientation, skid footprint, protection terminals, enclosure corrosion class, liquid containment and low-voltage connection to the inverter should be frozen as a standard block. A serialised test record then lets the EPC team install any accepted unit at any prepared location without reopening the design.

Transformer duty begins at the inverter

The inverter defines more than the low-voltage number. Its maximum continuous current, overload behaviour, harmonic spectrum, reactive-power capability and switching controls all affect transformer thermal and dielectric performance. The 3.75 MVA nameplate must therefore be checked against the complete operating envelope, not only the plant’s 90 MW export limit.

• Confirm winding voltage at the inverter’s hottest and coldest operating conditions.
• Evaluate harmonic losses using vendor spectrum data rather than a generic allowance.
• Coordinate MV fuses or breakers with transformer inrush and inverter fault contribution.
• Specify outdoor sound level, fluid system and corrosion protection for the actual site.

Procurement takeaway: approve one fully coordinated reference block first, then manufacture the repeated units against the same controlled drawings and inspection plan.