Question 1

What transformer is used in a solar farm?

Accepted Answer

Utility-scale solar farms use two main transformer types: inverter-duty step-up transformers (pad-mounted or dry-type) at each inverter block to raise inverter AC output to the plant's medium-voltage collector system (commonly 34.5 kV), and a high-voltage substation main transformer at the point of interconnection to step the collector voltage up to transmission level (110 kV or 220 kV) for grid connection.

Question 2

What's the difference between a step-up transformer and a standard distribution transformer for solar?

Accepted Answer

A solar inverter-duty step-up transformer is designed for the specific duty cycle of a PV plant: daily on/off thermal cycling as the sun rises and sets, harmonic content from inverter switching, and outdoor exposure. A standard distribution transformer is designed for steady-state loading and may not be rated for the thermal cycling or harmonic spectrum of a solar inverter output without derating.

Question 3

What is an inverter-duty transformer?

Accepted Answer

An inverter-duty transformer is specifically designed to interface with the AC output of a solar (or other) inverter. Key design features include harmonic tolerance (the winding insulation and core are engineered for the inverter's switching harmonic spectrum), thermal cycling capability (daily on/off without accelerated insulation aging), and appropriate impedance for the inverter's grid-forming requirements.

Question 4

What capacity and voltage do I need for a utility-scale PV plant?

Accepted Answer

Inverter-duty step-up units are typically sized per inverter block — commonly 1,000–4,000 kVA per unit depending on the inverter configuration and block layout. The substation main transformer is sized to the plant's total AC output and the utility's interconnection study requirements. Interconnection voltage is typically 110 kV or 220 kV for utility-scale plants. Contact Seatrust with your plant capacity, inverter block sizing, and interconnection requirements for a sized solution.

Question 5

What standards apply to solar farm interconnection transformers?

Accepted Answer

Solar farm transformers are typically built to IEEE C57.12 series (with UL/CSA listing for North American projects) for distribution-level units, and IEC 60076 / GB/T 1094 for high-voltage substation main transformers. Grid interconnection requirements follow IEEE 1547 in North America. Seatrust can supply to either standard family depending on your project's location and utility specification.

Solar Farm Transformers | PV Step-Up & Substation | Seatrust