Utility interconnection
Substation and padmount units built to the interconnection spec
An interconnection is the one project where the specification is not yours alone — the utility's requirements on impedance, tap range, protection and test evidence are conditions of energisation. Equipment that cannot produce the paperwork does not get connected.
What drives the specification
The spec is written by someone else
Voltage class, impedance, tap range, vector group and accessory list usually arrive from the utility rather than from the buyer. Substation and power transformers here are made to order against exactly that document, two- or three-winding, typically 2 to 60 MVA and up to 110 kV class, with de-energized taps or a full on-load tap changer as the spec requires.
Test evidence is part of the deliverable
Routine tests run per IEEE C57 or IEC 60076 in a CNAS-accredited transformer test station — ratio, resistance, impedance, losses, applied and induced voltage. Medium- and high-voltage units additionally pass through a shielded partial-discharge test room. Factory acceptance testing can be witnessed remotely, which removes a trip from the schedule without removing the verification.
Impedance is a system decision
Impedance sets the available fault current at the secondary and therefore the interrupting duty on everything downstream. It is quoted against your written specification rather than picked from a standard list, and the one-line gets an engineering review before any number is committed.
Typical specification
- Substation units
- Liquid-immersed, two- or three-winding, typically 2–60 MVA
- Voltage class
- Up to 110 kV class, confirmed at engineering review
- Cooling
- ONAN / ONAF
- Tap control
- De-energized taps or on-load tap changer (OLTC)
- Accessories
- Conservator, Buchholz relay, gauges, monitoring per spec
- Distribution side
- UL-listed padmount, 45–4,000 kVA, file E526441
What to send us
Send the utility's specification document and the one-line. Impedance, tap range and the accessory list are quoted against it directly, and the engineering review comes back with the quote rather than after the order.
Product lines for this application
Padmount Transformers
UL-listed, liquid-filled, 45-4,000 kVA
Dead-front, loop or radial feed, mineral oil or FR3-type fluid. UL file E526441, built to IEEE C57.12.00 / C57.12.28.
View the line →Substation Transformers
Medium- and high-voltage units, built to project spec
Liquid-filled substation and power transformers for utility interconnects and large loads, factory-tested in a CNAS-accredited test station.
View the line →Working on a utility interconnection project?
Send the one-line and load list. Engineering review is part of every quote, and pricing comes back within one business day.