35kV OLTC Transformer Selection Guide
Reviewed by the Fengguang engineering team · Last updated 10 Nov 2026
Voltage regulation under load for 35 kV industrial and utility networks. This guide covers the selection inputs, typical configuration and the questions to settle before the datasheet is approved.
What this family covers
Voltage regulation under load for 35 kV industrial and utility networks.
On-load tap-changing (OLTC) transformers regulate the secondary voltage while the load is energised. They are used where the incoming voltage varies, where the load is cyclic, or where a fixed tap cannot keep the downstream voltage inside limits. Fengguang builds 35 kV OLTC transformers from 1,000 to 31,500 kVA for industrial main substations, utility distribution and renewable-energy step-up. The design combines
How to select
Start with the load in kVA, the voltage class, the fault level and the site conditions. Then choose the loss level, cooling, winding material, tap range and enclosure. Do not select from a catalogue without those inputs.
Typical configuration
Most projects start from a standard 35kV OLTC Transformer platform and adapt the cooling, terminals, protection and finish. The approved datasheet fixes the guaranteed values.
Questions to settle before the datasheet
Confirm the load profile, voltage ratio, tap range, impedance, fault level, cooling stage, ambient, altitude, enclosure, corrosion class, termination and test scope. These are the inputs that change the design.
Acceptance checks
Check the nameplate data, routine test report, dimensions, weight, painting, accessories and packing against the approved drawing. For critical projects, add a witnessed test and a document review.
| Input | What to confirm |
|---|---|
| Capacity | kVA and load profile |
| Voltage | Class, ratio and tap range |
| Losses | No-load and load loss |
| Cooling | ONAN/ONAF or AN/AF |
| Environment | Ambient, altitude, IP and corrosion |
FAQ
How do I choose a 35kV OLTC Transformer?
Start from maximum demand, voltage class, fault level and site conditions. Then compare losses, cooling, dimensions and protection as a system.
Can the transformer be customised?
Yes. Winding material, losses, cooling, terminals, enclosure and finish are project options, confirmed on the approved datasheet.
What should be in the quotation?
Guaranteed losses, impedance, tap range, cooling stage, dimensions, weight, test scope, documents and delivery basis.
What is the most common selection error?
Sizing on connected load, ignoring ambient/altitude, or comparing models only on purchase price instead of total owning cost.
Related pages
Need this applied to a project?
Send the application, voltage class and site conditions through the inquiry form. The team will check the transformer family and the document scope.
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