Grid transformers sit at the nodes where transmission voltage is handed over to distribution networks. Hebei Youge builds oil-immersed units from 6.3 MVA to 63 MVA at 35kV, 66kV, and 110kV, delivered as complete packages with on-load tap changers, protection interfaces, and full routine test documentation.
35-110kV 6.3-63MVA IEC 60076
| Specification | Value |
|---|---|
| Winding material | Copper, or aluminium on request |
| Insulation class | Class A oil-immersed |
| Bushing type | Porcelain / composite, CT-equipped |
| Protection | Buchholz, WTI, OTI, PRD, oil level |
| Monitoring | Optional winding fibre optic, DGA port |
| Surface treatment | Sandblast + epoxy primer + PU topcoat |
| Ambient range | -25°C to +45°C (lower on request) |
| Delivery | 30 days from drawing approval |
Where Grid Transformers Are Installed
A grid transformer is specified against the network it serves, not against a catalogue. The three applications we build for most often are transmission intake substations, primary distribution substations feeding 11kV or 33kV feeders, and industrial intakes where a plant is connected directly at transmission voltage. Each carries a different short-circuit impedance and vector group requirement, so the winding design is fixed after we see the single-line diagram rather than before.
Selecting Rating and Impedance
Impedance is the first number to settle because it drives fault level, voltage regulation, and parallel operation. A 10% impedance passes higher fault current and gives tighter regulation; 16% to 18% restrains fault current at the cost of a larger voltage drop under load. Where two units run in parallel the impedances must match within tolerance or the units will not share load correctly. We calculate both and confirm the value on the drawing before manufacture.
Technical Highlights
- Copper windings with transposed conductors on high-current LV
- ONAF cooling stage for a second rating step where specified
- OLTC with motor drive, local and remote control
- Low partial discharge winding design and processing
Application Scenarios
- Transmission intake substations at 66kV and 110kV
- Primary distribution substations feeding 11kV or 33kV
- Industrial plant intakes connected at transmission voltage
- Renewable grid connection and collector substations
Key Features
- Full routine tests per IEC 60076 with reports in English
- Sealed conservator or hermetically sealed options
- Corrosion protection specified for coastal and industrial sites
- Prepared for online DGA and fibre optic winding monitoring
Optional Configurations
- On-load tap changer with voltage regulating relay
- Forced oil and forced air cooling stages
- Neutral grounding resistor or reactor marshalling
- Sound enclosure for low-noise installations
Routine and Type Testing
Every unit leaves the works with winding resistance, ratio and vector group checks, insulation resistance, dielectric tests, no-load and load loss measurement, temperature rise, and a full dielectric test sequence witnessed or documented as agreed. Because the grid transformer is usually the longest-lead item on a substation project, the test slot is booked with the manufacturing slot so that inspection does not sit behind production.
Related Products and Pages
- Step-up transformers for generator and renewable connection
- Step-down transformers from 33-132kV to 11kV
- Power transformer range
- High-voltage transformers
- Build a quote list for multiple units
Frequently Asked Questions
What sizes do you build for grid applications?
6.3 MVA to 63 MVA at 35kV, 66kV, and 110kV. If your project needs a rating outside this range, send the specification and we will confirm what we can build against it.
Can the transformer be supplied with an OLTC?
Yes. On-load tap changers with motor drive and automatic voltage regulating relay are available, as are off-circuit tap changers where the network does not need regulation under load.
Do you provide type test reports?
Routine test reports are issued for every unit. Type test reports are available for the design series and we can arrange witnessed testing at the works.
How long is delivery?
30 days from drawing approval for standard ratings. Larger or highly specified units are quoted against a project programme.
Can you match an existing transformer for replacement?
Yes, and this is common for substation replacements. Send the existing rating plate and drawings and we will match rating, impedance, vector group, and terminal arrangement.