- 1Primary switch
- 2Transformer & radiators
- 3Throat connection
- 4Secondary switchboard
Unit Substation Transformer
The heart of a unit substation: a liquid-filled transformer with throats or flanges on both sides, built to bolt to your primary switch and secondary switchboard. 300 – 5,000 kVA, ONAN with optional fans.
Switch, Transformer and Switchboard as One Unit
A unit substation brings power in at medium voltage and hands it out at utilization voltage in one continuous lineup. The transformer sits in the middle, with a throat on one side that bolts to the primary load-break switch or breaker, and a throat on the other that bolts to the secondary switchboard or switchgear. No exposed cable runs, a smaller footprint and one coordinated design. We build the transformer and can supply the switchgear on either side.
- Flanged throats or air terminal chambers on either side
- Coordinated with CANDRON MV switchgear and LV switchboards
- Fan package for extra capacity at peak load
- Load tap changer or de-energized taps
- Mineral oil or FR3 natural ester
- Indoor or outdoor installation
Unit Substation Transformer in plain words
What it does
A substation-style transformer with flanged throats on each side, so the medium-voltage switch and the low-voltage switchboard bolt straight onto it as one lineup.
Pick it when
- You are building a plant, hospital or campus main electrical room or yard
- You want the MV switch, transformer and LV switchboard as one coordinated lineup
- You need fan cooling for extra capacity
Better choice if…
You only need a stand-alone unit fed by underground cable
See the Three-Phase Padmount →What's Included
- Side-wall HV and LV bushings in throats or flanges
- Primary de-energized tap changer, 2 × 2.5% above and below
- Welded tank with radiators, nitrogen blanket or sealed tank
- Pressure relief device, liquid level, temperature and pressure/vacuum gauges
- Drain and sample valve, ground pads, lifting and jacking provisions
- Copper or aluminum windings
- ANSI 61 grey finish
- Nameplate and wiring diagram to CSA
- +ONAF fan package with controls
- +Integral primary load-break switch
- +Winding temperature indicator and gauges with alarm contacts
- +Sudden pressure relay
- +Surge arresters
- +Close-coupled CANDRON MV switchgear and LV switchboard
Full Specifications
| Parameter | Value |
|---|---|
| Rating | 300 – 5,000 kVA ONAN; higher with fans |
| Primary voltage | 2.4 – 34.5 kV |
| Secondary voltage | 208Y/120 V to 4.16 kV |
| Connections | Throat, flange or air terminal chamber, either side |
| Cooling | ONAN; ONAF with fan package; KNAN with FR3 |
| Fluid | Type II mineral oil, or FR3 natural ester (less-flammable, biodegradable) |
| Temperature rise | 65 °C average winding rise (55/65 °C dual rating optional) |
| Impedance | 5.75% typical; to suit fault study |
| Taps | 2 × 2.5% above and 2 × 2.5% below nominal, de-energized tap changer |
| Tests | Routine tests per IEEE C57.12.90 and CSA C2.1: ratio, polarity and phase relation, winding resistance, no-load and load losses, impedance, applied and induced potential, leak test |
Built to Standard
Where It's Used
- Hospital, university and government campuses
- Industrial plants and process facilities
- Data centre and telecom main electrical rooms
- Water and wastewater plants
- Mines and mills
From design and specification through factory testing, commissioning, and ongoing maintenance — CANDRON delivers at every phase.
- Engineering drawings and coordination studies
- Factory acceptance testing (FAT) with full reports
- Site commissioning and protection settings
- Spare parts, training, and maintenance support
Common Questions
A padmount is a self-contained cabinet fed by underground cable. A unit substation transformer is built to bolt directly to switchgear on both sides, making one lineup — the usual choice for a facility’s main electrical yard or room.
A fan package typically lifts the rating by about 15% on smaller units and 25% on larger ones, giving headroom for peak loads without buying a bigger transformer.
Mineral oil is the economical standard. FR3 natural ester is made from vegetable oil: it is biodegradable, has a fire point above 300 °C (a “less-flammable” fluid), and slows paper insulation ageing. Choose it near buildings, water, or anywhere the fire code or environmental permit asks for a less-flammable fluid.
Ready to Spec
Your Project?
Our engineering team responds with specs, lead times, and pricing the same day. Tell us what you need:
- kVA rating (and fan rating)
- Primary and secondary voltages
- Throat, flange or cable connection on each side
- Switchgear make or CANDRON-supplied
- Indoor or outdoor
- Site location
Send us your project details and we'll respond with a price, lead time, and any clarifying questions — typically within a few hours.
Request a Quote →Or call +1 (647) 616-2595