Custom 11kV-35kV Step-Up Transformers: Tailored Oil-Immersed & Dry-Type Solutions | CHBEB

Introduction

Standard transformers often don’t meet important needs. The outcome is extra effort, lost time, and money. Custom 11–35 kV step-up transformers fix voltages, footprints, and duties that aren’t conventional. They make connections safer, work more efficiently, and cost the least over the life of the project.

Why Get a Custom Transformer? The Value Proposition

Off-the-shelf systems have trouble with strange voltages, limited space, and environmental dangers. These gaps lead to change orders and time off work. Custom engineering makes sure that electrical, mechanical, and compliance demands are all met from the start. This lowers risk, boosts performance, and protects budgets for decades.

Finding solutions to power and space problems that aren’t standard

Instead of making the site fit the transformer, custom designs take into account real-world limitations. Some of the problems we solve are:

• Hybrid systems, specialized phase shifts, neutral availability, and grounding techniques are all examples of non-standard voltages and vector groups
• Tight footprints and weight limits: small tanks, low-profile radiators, or split modules for pads and rooftops that don’t have a lot of space.
• Extreme environments: Marine-grade coatings (C5-M)¹, sealed bushings, wildlife guards, sand/salt mitigation, and cores that don’t make a lot of noise.
• Grid-code details: Tap ranges (±2×2.5% or wider), impedance targets, BIL coordination, and pairing of arresters.
• Operational limits include high altitudes, high ramp rates, frequent cycling, and harmonics from VFDs or inverters.

Getting the best performance and lowest total cost of ownership (TCO)

The cheapest up front isn’t always the cheapest to own. Customization lowers losses, makes insulation last longer, and stops outages. Make money off of savings:

• Loss packages: Make sure there are no assured losses while the load is on or off. A few hundred watts saved running 24/7 for decades.
• Thermal design: ONAN/ONAF stages, RTDs, and hotspot control to keep insulation from breaking down while ramping and cycling.
• Serviceability: standard bushings and elbows, easy access to taps, and spare parts kits reduce down on MTTR and labor.
• Natural ester can be a better alternative for fire protection and the environment than mineral oil².

Making Your Own Solution: Oil-Immersed or Dry-Type

Choosing the improper construction might lead to safety issues or inefficiencies. The rules and duties for each site are different. Pick the dielectric and enclosure that meet your fire strategy, environment, and lifespan goals to prevent having to rework them later.

Custom Oil-Immersed Transformers: The Best Choice for Power and Longevity

Oil-immersed designs work best outside and at higher kVA levels since they take up less space and have significant thermal inertia. You can choose from the following:

• Voltage systems: from 0.48 to 1.0 kV for LV and from 11 to 35 kV for MV; Dyn/YNd groups per grid code.
• Cooling: ONAN base with ONAF fans and ducts for oil to flow to hotspots.
• Loss targets: Optimized core/winding geometry and high-quality steel to stay within the loss caps set by the tender.
• Mineral oil is cheap, and natural ester has a high fire point and breaks down naturally.
• Mechanical: Low-noise clamps, vibration isolators, and corrosion systems for sites along the ocean or in the desert.

Best for utility yards, collecting renewable energy, heavy industrial work, and projects that put a high value on efficiency and overload margin.

Custom Dry-Type Transformers: For Safety and Special Situations

Dry-type (VPI/cast resin)³ works best when liquids are limited or when you need to set up quickly indoors. Some of the things you can change are:

• Ingress and ventilation: Enclosures with filtered airflow, IP ratings, and cooling routes that go where they need to go.
• Fire and smoke profile: Cast-resin systems that work well in tunnels, hospitals, transit systems, and high-rise basements.
• Acoustics: Quiet zones with low-flux-density cores, dampening kits, and enclosure liners.
• Form factor: Doors, lifts, and mezzanines have height and width limits, and the components can be put together in different ways.

Perfect for malls, universities, data-adjacent rooms, and areas where liquids are not allowed.

The Steps: Getting an Estimate for Your Custom Transformer

Unclear RFQs lead to delays and modification orders. Clear, engineering-ready briefs speed up pricing, approvals, and delivery, which lowers project risk and total cost.

A checklist for success with your custom design brief

To get quick and accurate quotes, please give the following:

• Electrical: kVA, LV/HV voltages, vector group, goal %Z, tap range, short-circuit levels, and how to ground it.
• Load profile: duty cycle, ramps, overload limits, harmonics limitations, and the existence of an inverter or VFD.
• Environment: indoor/outdoor, ambient/altitude, corrosion category, dust/salt, animal concerns, and noise limits.
• Protection: Bayonet/CL fuses, MV surge arresters, PRV/RPRR, relays, and fault indicators.
• Compliance: IEC 60076 / IEEE C57, CE/UL needs⁴, type/special tests, and witness testing.
• Mechanical and logistics: maximum footprint, height, and weight; lifting paths; pad specifics; delivery access; and required ship date.
• Operations: spare parts kit, paperwork set, warranty expectations, and monitoring (RTDs, oil/moisture sensors).

Our Customization Process: From Idea to Delivery

1. Discovery and scoping: Make sure you know your responsibilities, the environment, and the rules. Also, set success measures like losses, noise, and footprint.
2. Thermal, electrical, and mechanical models; preliminary GA drawings; and forecasts of loss and efficiency are all part of pre-engineering.
3. Quotation and TCO: Itemized prices with alternatives (copper vs. aluminum, ester vs. mineral oil) and loss capitalization.
4. Design freeze: Final drawings, tap settings, protection, coatings; factory test plan agreed.
5. Manufacture and FAT: routine and type testing according to standards; optional witness; shipping preparation and preservation.
6. Delivery and SAT include site checks, terminations, commissioning tests, baseline thermography, and handing over documents.
7. After the sale: spare parts, monitoring dashboards, a schedule for maintenance, and performance reports.

Conclusion

Custom 11–35 kV step-up transformers are not just special order equipment — they are the only way to align real-world site limits with strict grid requirements.

For professionals

Customization ensures that electrical parameters (kVA rating, impedance, vector group), thermal design, and compliance certifications are precisely matched to project needs. This reduces risk, avoids costly redesigns, and secures the lowest Total Cost of Ownership (TCO) across decades of operation.

For beginners

Think of it like tailor-made shoes. Standard shoes may pinch or feel loose, and problems show up over time. A custom-made pair costs a bit more upfront but delivers comfort, durability, and peace of mind. In the same way, a custom transformer designed for your site keeps power reliable, safe, and efficient.

In short: By defining clear requirements, selecting the right materials, preparing a structured RFQ, and applying TCO thinking, you secure more than a transformer — you gain a long-term guarantee of safety, efficiency, and reliable power.

1. Corrosion categories and protective coatings — ScienceDirect ↩︎
2. Natural Ester Dielectric Fluid for Transformers — IEEE Xplore ↩︎
3. Dry-type transformer — Wikipedia ↩︎
4. IEC 60076 Power Transformer Standards — IEC ↩︎

Learn More

Want to explore more transformer solutions? Download our latest product catalog or browse our product categories to find the right transformer for your project.

📥 Download Product Catalog 🔎 Browse Product Categories