China Oil-immersed Transformer Factory
Oil-immersed distribution and power transformers, engineered around your utility, industrial, substation, and renewable energy projects.
Send us your voltage, capacity, impedance, vector group, and cooling needs. We custom-configure every unit to match exactly what your project requires.
What You Get
Looking for an Oil-immersed Transformer Factory in China?
Yes, we're a China-based oil-immersed transformer factory serving utility companies, industrial plants, solar and wind farms, mining sites, and EPC contractors worldwide. Whatever your project needs, we manufacture oil-immersed distribution and power transformers built to your spec: custom voltage class, capacity, vector group, impedance, and cooling method (ONAN, ONAF, OFAF). Every unit ships with the protection accessories you specify (Buchholz relay, oil temperature indicator, pressure relief, MOG) and a full set of factory test reports under IEC 60076. Send us your single-line diagram or technical sheet, and Hank gets back to you with quotation, drawings, and build timeline within 24 hours.
What You'll Find on This Page
Jump straight to what matters for your project, from product range and applications to factory testing, ordering process, and FAQ.
Inside Our Transformer Factory
Every transformer for your project is produced, assembled, tested, and inspected inside our own manufacturing facility before shipment. You're working directly with the factory floor, not a trading desk, for utility, industrial, substation, and renewable energy projects.
Built In-House. Tested Before Shipment.
Your transformer is engineered, manufactured, and certified entirely inside our facility, ready to drop straight into your project on arrival.
- Factory Manufacturing
- Routine Testing
- Custom Production
- IEC Standard
- Project Support
- Export Experience
Oil-immersed Transformers We Manufacture
Find the transformer that matches your project, from distribution networks and substations to industrial plants and renewable energy sites. Every unit is custom-configured to your spec.
Oil-immersed Distribution Transformer
Power your utility distribution lines, commercial buildings, and industrial sites with reliable step-down transformation.
Oil-immersed Power Transformer
Engineered for substations, power plants, and large-scale transmission projects, with the capacity your grid needs.
Hermetically Sealed Transformer
Skip oil maintenance entirely. The sealed-tank design keeps your outdoor and utility installations running without scheduled servicing.
Conservator Type Transformer
Run continuously at higher capacities. The conservator tank handles oil expansion for substations with demanding load profiles.
11kV / 33kV Transformer
The voltage classes you need most. Built for utility distribution networks, solar farms, and wind project step-up needs.
Low-loss Transformer
Cut your operating cost over the lifetime of the unit. Reduced no-load and load losses keep your utility bill and carbon footprint down.
Built for Different Power Projects
Find the application that matches your job site. We engineer oil-immersed transformers around your real operating environment, whether that's a utility grid, a substation, a solar farm, or a mining operation.
Utility Distribution Networks
Keep urban, rural, and regional grids running with low-loss transformers built for decades of continuous duty.
- 11kV and 33kV voltage classes
- Low no-load and load loss
- Outdoor pole and pad-mount ready
Substations & EPC Projects
Lock in custom transformer specs for substation builds, grid expansions, and infrastructure tenders, with the documents your audit will need.
- Custom voltage and vector group
- Full IEC 60076 documentation
- EPC milestone-aligned delivery
Solar Power Plants
Step up your PV output reliably. Outdoor-rated transformers built to handle harmonic stress and 25+ years of daily cycling.
- Outdoor IP-rated tank
- Harmonic-tolerant design
- ONAN / ONAF cooling
Wind Power Projects
Match your variable wind load with transformers built for cyclical duty and exposed-site weather, onshore or coastal.
- Variable load profile rated
- Marine-grade coating option
- Reinforced sealing for harsh weather
Industrial Manufacturing Plants
Power your continuous production line, heavy motors, and welding loads without sagging voltage or unexpected downtime.
- Motor inrush tolerance
- 24/7 continuous duty rated
- Low-downtime design philosophy
Mining & Harsh Environments
Survive high heat, dust, humidity, and altitude. Reinforced mechanical structure and sealed design built for the toughest jobs.
- High temperature operation
- IP-rated dust and humidity sealing
- Altitude-corrected insulation
Your Project Conditions, Our Engineering Spec.
You won't get an off-the-shelf transformer. Every unit is configured around your voltage class, site environment, and operating profile, so what lands on your project is what fits.
- Project Site Survey
- Custom Voltage Class
- Environmental Adaptation
- IEC 60076 Compliance
- Drawing Pre-Approval
- On-Time Project Delivery
Drawings & quotation back within 24 hours
Why Buyers Choose Our Factory
Transformer procurement isn't just price comparison. Wrong specifications, unstable operation, missing documentation, or unreliable testing can wreck your project timeline and saddle you with long-term operating headaches. We focus our factory support on helping you reduce that risk, before production, during manufacturing, and before your unit ships.
Engineering Review
Before Production
Technical Review Before Manufacturing
Your transformer's reliability starts on the spec sheet. Wrong voltage ratio, impedance, vector group, cooling method, or installation environment, and your project hits delays before production has even started.
Our engineering team reviews your project requirements before manufacturing, so spec mismatches, installation conflicts, and approval setbacks don't blindside you mid-execution.
Routine Testing
Before Shipment
Factory Testing Before Shipment
Before your unit ships, routine testing verifies the performance, insulation condition, and electrical parameters your project actually needs, under IEC 60076.
You receive routine test reports, electrical test records, and inspection documents before the truck leaves the gate. For projects requiring third-party or witness inspection, factory acceptance testing is also on the table.
Project Documentation
Project Approval
Support for EPC and Utility Documentation
Your utility or EPC review needs a paper trail. Technical drawings, datasheets, compliance documents, and test records have to land on the right desk before equipment approval.
You'll get the datasheets, GA drawings, nameplate drawings, test reports, manuals, and engineering documents your reviewers expect, ready when your project needs them.
Long-term Operation
In Service
Designed for Long-term Operation
Your transformer doesn't get to rest. Continuous load, temperature swings, and outdoor environments hammer industrial, substation, and renewable installations every single day.
Design, insulation control, leakage inspection, and material selection are managed to keep your unit running and your maintenance budget stable across its full service life.
Custom Configuration
Project Fit
Flexible Configurations for Different Projects
Your grid is not the same as the next project's. Local standards, installation environments, and operating conditions all change what the right transformer spec actually looks like.
Voltage class, capacity, tapping range, impedance, cooling method, protection accessories, and coating systems are all adjustable to match what your project requires, not what's easiest for us to build.
Direct Communication
Throughout Order
Direct Communication with the Factory Team
You shouldn't have to chase a trading desk for answers. Specs, drawings, testing requirements, production progress, shipment timing, you talk directly to the factory team that's building your unit.
That cuts response time during quotation, manufacturing, and execution, and removes the layer where most procurement mistakes happen.
Oil-immersed Transformer Manufacturing Process
Your transformer's long-term reliability comes down to material control, insulation handling, assembly accuracy, and testing discipline at every step. Production, assembly, drying, oil treatment, and final testing all happen inside our factory before your unit ships.
01
Silicon Steel Core Processing
Silicon steel sheets are cut and stacked to keep your transformer's no-load losses low and magnetic flux clean. Core accuracy directly shapes the efficiency, temperature rise, and operating stability you'll see on site.
02
HV and LV Coil Winding
HV and LV windings are wound to your confirmed electrical parameters and insulation requirements. Winding quality is what holds your voltage stable, your insulation safe, and your unit standing up to short-circuit events.
03
Insulation Assembly
Insulation goes in between windings, core structures, and conductive parts to hold dielectric strength under long-term load. This is the step that quietly decides whether your transformer survives ten years or twenty-five.
04
Core and Coil Assembly
Core and winding assemblies are integrated and mechanically locked down before drying. Assembly precision here is what controls vibration, insulation reliability, and how stable your unit runs once it's energized.
05
Vacuum Drying Process
Vacuum drying pulls moisture out of the insulation before oil filling. Skip this discipline and you compromise dielectric strength, accelerate aging, and shorten the service life your project is counting on.
06
Tank Fabrication and Welding
Tanks are fabricated, welded, leak-tested, and surface-treated. Structural strength and sealing quality keep your outdoor unit dry and prevent the oil leakage problems nobody wants to deal with on a remote site.
07
Oil Filling and Filtration
Transformer oil is filtered and filled under controlled conditions to protect insulation performance and keep contamination out before final assembly and testing.
08
Routine Factory Testing
Electrical routine testing verifies your transformer's performance, insulation condition, and compliance with your project specs, before the unit ever leaves the factory gate.
Manufacturing Control for Long-term Reliability
Material inspection, insulation control, assembly procedures, and routine testing are managed throughout production, so the operational risks waiting at your installation and across long service life get caught here, not on your site.
- Material Inspection
- Insulation Control
- Assembly Procedures
- Routine Testing
- Leakage Inspection
- Pre-Shipment Verification
Process documents and test records available
Quality Control Throughout Production
Your transformer's reliability isn't decided at a single test station, it's controlled at every stage. Inspection procedures cover materials, insulation, assembly, and electrical testing across the whole manufacturing process before your unit ships.
Current Control Point
Incoming Material Inspection
Inspection Control Before Shipment
Material inspection records, in-process inspections, and routine testing procedures are managed throughout manufacturing. Before your transformer is prepared for delivery, the documentation trail is complete and ready for your audit.
08
Control Points
100%
Routine Tested
IEC 60076
Standard Compliant
Full
Test Records
Factory Testing Before Delivery
Routine electrical testing is completed before shipment to verify your transformer's performance, insulation condition, and electrical parameters against project specs and applicable standards. Testing isn't a checkbox, it's the risk insurance that protects your commissioning timeline and long-term operation.
Routine Tests
Routine testing is completed on every transformer before shipment to verify electrical performance, insulation condition, and operational parameters. No unit leaves the gate untested.
Type & Special Tests
Additional testing can be arranged for your project spec, utility requirements, or consultant approval procedures, including temperature rise and lightning impulse where required.
FAT & Witness Inspection
Factory acceptance testing support is available for your representatives, EPC contractors, and third-party inspection agencies. Travel, scheduling, and witness coordination, we handle it.
Real Testing, Real Records
Detailed Test Items per Unit
Every transformer that leaves our facility carries this routine test record. Type and special tests are added on request when your project, utility, or consultant requires them.
Winding Resistance Test
Verifies winding conductor condition and connection consistency.
Voltage Ratio Test
Checks transformer voltage ratio accuracy against your design specs.
Vector Group Verification
Confirms phase displacement and connection configuration before operation.
No-Load Loss & Current Test
Measures core losses and excitation current during no-load operation.
Load Loss & Impedance Test
Verifies load performance and impedance values under operating conditions.
Applied Voltage Withstand Test
Checks insulation strength under specified high-voltage conditions.
Induced Voltage Withstand Test
Verifies inter-turn insulation performance and winding integrity.
Insulation Resistance Test
Measures insulation condition before shipment and commissioning.
Oil Dielectric Strength Test
Checks transformer oil insulation performance before delivery.
Leakage Inspection
Verifies tank sealing condition and oil leakage prevention.
Temperature Rise Test
On RequestAvailable for project performance verification when required.
Lightning Impulse Test
On RequestAvailable for utility and EPC project specifications.
See the Test Reports Before You Order.
Want to know exactly what test documents will land in your inbox with your transformer? Request sample reports and we'll send you a real, redacted set so you can verify the format, parameters, and scope of testing before the PO goes out.
- Sample Routine Test Report
- Sample FAT Protocol
- IEC 60076 Compliance
- Witness Test Available
Sample reports emailed within one business day
Custom Transformer Solutions for Different Projects
Your project conditions are not generic, and your transformer shouldn't be either. Voltage class, capacity, impedance, cooling method, vector group, and protection configurations are all adjustable to match your grid, your site, and your operating requirements.
Rated Capacity
Transformer capacity configured to your project load and future expansion needs, so you're not paying for headroom you won't use or boxed in when demand grows.
Primary & Secondary Voltage
Voltage ratio configured to your utility grid voltage and equipment requirements. Whatever your incoming and outgoing voltages need to be, we build to it.
Vector Group
Connection configurations adjusted to your system design and operating conditions. Phase displacement matches what your grid actually needs.
Impedance Voltage
Impedance values configured for your short-circuit performance and system coordination requirements. Critical for safe parallel operation.
Cooling Method
ONAN, ONAF, or dual-rated cooling configurations available based on your operating load profile and site conditions.
Tapping Range
Off-circuit or on-load tap changer configurations for your voltage regulation requirements, with custom step ranges available.
Installation Environment
Design adjustments for your site conditions: high temperature, coastal humidity, heavy dust, or high altitude. The environment doesn't compromise reliability.
Protection Accessories
Protection and monitoring accessories configured for your project's operating requirements, from basic to fully instrumented setups.
Not Sure About a Parameter? Send What You Have.
Single-line diagram, technical datasheet, utility requirement letter, RFQ document, whatever you have. Our engineering team reviews it, fills in the gaps with you, and comes back with a complete proposal.
- Single-Line Diagram
- Datasheet
- Utility Letter
- RFQ Document
Protection Accessories and Monitoring Options
Protection and monitoring accessories are what keep your transformer safe and your maintenance team informed. Configurations adjust to your project requirements, operating environment, and utility standards, basic to fully instrumented.
Monitoring
Oil Temperature Indicator
Tracks oil temperature in real time so overheating is caught before it shortens insulation life or triggers an unplanned shutdown.
Monitoring
Winding Temperature Indicator
Reads winding temperature directly, giving you load-management precision and a second layer of thermal protection beyond oil temperature.
Safety
Pressure Relief Valve
Vents internal pressure under abnormal conditions to prevent tank rupture. The last-line safety device that protects your installation and people on site.
Safety
Buchholz Relay
Detects gas accumulation and abnormal oil flow inside conservator-type transformers, flagging internal faults before they escalate to insulation failure.
Monitoring
Oil Level Gauge
Visual oil level check during operation and routine maintenance, with optional alarm contacts to flag low or high oil conditions for your control room.
Protection
Dehydrating Breather
Strips moisture from the air entering the conservator during oil expansion and contraction, keeping the insulation system dry and dielectric strength stable.
Regulation
Tap Changer
Off-circuit (OCTC) or on-load (OLTC) configurations let you fine-tune voltage output to match grid fluctuations or load swings without dropping service.
Control
Control Cabinet
Centralized marshalling and control connection point for all monitoring devices, ready to wire into your SCADA or substation control system.
Configurable per project: All eight accessories above are options, not mandatory bundles. Tell us what your utility, EPC contract, or operating standard requires, and we configure only what your project actually needs.
Reducing Procurement and Operating Risks
Transformer procurement isn't just about getting equipment delivered. Wrong specifications, installation problems, operational failures, and incomplete documentation can all hit your project with delays, maintenance costs, and operating headaches. Technical review, manufacturing control, and factory testing are how we catch those risks before your unit ships.
Engineering Review
Wrong Transformer Specifications
Wrong voltage ratio, impedance, vector group, or cooling configuration is the kind of mistake that doesn't show up until your transformer is already on site. Then you're looking at re-work, replacement, or worse, a unit that doesn't fit your project at all.
How We Reduce It
Project specifications, application conditions, and technical parameters are reviewed by our engineering team before production starts. Configuration mismatches and project delays are caught at the desk, not the site.
Support Before Production and Shipment
Technical review, manufacturing control, testing procedures, and engineering documentation, you get all four working together to coordinate your project and shrink the installation and operating risks waiting at your site.
- Technical Review
- Manufacturing Control
- Factory Testing
- Engineering Documentation
- Project Coordination
- Risk Reduction
Engineering proposal returned within 24 hours
Engineering Documents for Project Approval
Your project doesn't get commissioned just because the transformer is on site. Technical drawings, testing records, and engineering documents have to clear approval first. We prepare the documentation set your procurement, engineering review, and site preparation teams will actually use.
Technical Drawings
General arrangement, nameplate, foundation, and connection drawings prepared to your project's specific requirements, ready for your engineering review.
- GA Drawing
- Foundation Drawing
- Nameplate Drawing
- Wiring Diagram
Technical Specifications
Datasheets and parameter documents prepared for your engineering review, quotation confirmation, and project approval workflow.
- Technical Datasheet
- Specification Sheet
- Compliance Statement
- Deviation Sheet
Testing and Inspection Documents
Factory testing records and inspection documents prepared before shipment, ready for your project verification and commissioning team.
- Routine Test Report
- FAT Documents
- Inspection Records
- Oil Test Report
Shipping and Installation Documents
Project and shipment documents prepared to support your delivery, customs clearance, installation, and operation preparation.
- Packing List
- Installation Manual
- Operation Manual
- Certificate of Origin
Documentation Support for EPC and Utility Projects
Document preparation is coordinated to match your project specs, consultant requirements, and utility approval procedures before shipment. The paperwork your reviewers want, in the format they want it, when they need it.
- EPC Submittals
- Utility Approval Format
- Consultant Review
- Customs & Shipping
Transformers in Real Projects
A snapshot of where our oil-immersed transformers are running today, from utility distribution networks and EPC substations to solar farms and industrial plants. Filter by application to find projects similar to yours.
Utility
2024
Rural Distribution Network Expansion
Pole-mount and pad-mount distribution transformers supplied to expand utility coverage across rural communities.
Type
Distribution
Capacity
315 kVA
Voltage
33/0.4 kV
Substation & EPC
2024
110kV Substation Power Transformer
Power transformer supplied to an EPC contractor for a new 110kV substation serving urban load growth.
Type
Power
Capacity
40 MVA
Voltage
110/33 kV
Renewable Energy
2024
Solar Farm Step-up Transformer
Step-up transformer commissioned for a 50 MW utility-scale solar farm, harmonic-tolerant and IP-rated for desert conditions.
Type
Step-up
Capacity
25 MVA
Voltage
33/0.69 kV
Industrial
2023
Steel Mill Power Transformer
Heavy-duty power transformer for a steel mill with high motor inrush load and 24/7 continuous operation profile.
Type
Power
Capacity
20 MVA
Voltage
33/6.6 kV
Utility
2023
Urban Grid Upgrade
Batch supply of hermetically sealed distribution transformers for a city grid modernization project.
Type
Sealed
Capacity
630 kVA
Voltage
22/0.4 kV
Renewable Energy
2024
Onshore Wind Project Transformer
Step-up transformer engineered for variable load and exposed coastal conditions with marine-grade coating.
Type
Step-up
Capacity
16 MVA
Voltage
66/0.69 kV
Substation & EPC
2023
220kV Grid Substation
High-capacity power transformer for a national grid substation with full IEC 60076 documentation package and customer witness FAT.
Type
Power
Capacity
80 MVA
Voltage
220/66 kV
Mining
2024
Copper Mine Power Supply
Altitude-corrected transformer for a copper mining operation at 3,200m elevation with reinforced dust sealing.
Type
Power
Capacity
12.5 MVA
Voltage
33/6 kV
Renewable Energy
2024
Distributed Solar Plant
Multiple-unit batch supply of step-up transformers for a distributed commercial PV portfolio across the region.
Type
Step-up
Capacity
2.5 MVA
Voltage
22/0.4 kV
Utility
2023
Rural Electrification Program
Government-backed rural electrification project supplied with low-loss distribution transformers and full IEC compliance documentation.
Type
Distribution
Capacity
200 kVA
Voltage
11/0.4 kV
Utility
2024
Commercial Pad-Mount Supply
Pad-mount transformer batch for commercial property utility connections across a metropolitan area.
Type
Pad-Mount
Capacity
500 kVA
Voltage
13.8/0.4 kV
Substation & EPC
2024
66kV Substation Upgrade
Power transformer for a 66kV substation upgrade, supplied with full FAT witness and IEC 60076 documentation package.
Type
Power
Capacity
30 MVA
Voltage
66/11 kV
No projects in this category yet. and we'll talk through similar work.
500+
Projects Delivered
45+
Countries Served
220kV
Max Voltage Class
80MVA
Max Capacity Supplied
Your Project Could Be the Next Case on This Page.
Different country, different grid code, different operating conditions, we've configured transformers for them. Tell us where your project sits and we'll point to the closest reference work and walk through what made it succeed.
- Reference Project Lookup
- Local Grid Code Support
- Similar Case Sharing
- Customer Reference Available
Reference matching usually takes one business day
Transformer Ordering Process
From your first message to your unit arriving on site, here's exactly how the process runs. Each step is coordinated, traceable, and visible to you, so there's no black box between sending your specs and seeing the test report.
Eight Steps, Zero Black Box.
Each step is owned by either you, our factory, or both of us together. You always know who's working on what, when status updates are coming, and what document lands in your inbox next.
Who Does What
You send or confirm
Steps 1, 3, 6, 8
We execute
Steps 2, 4, 5, 7
Both coordinate
Throughout the project
08
Steps
24h
Quote Reply
100%
Traceable
YOU
Send Project Requirements
Share your transformer specs, single-line diagram, or project requirements. RFQ, datasheet, or just a rough scope, we'll work with what you have.
WE
Technical Review & Quotation
Our engineering team reviews voltage, impedance, vector group, and site conditions, then comes back with quotation, lead time, and any spec questions, usually within 24 hours.
BOTH
Specification Confirmation
GA drawings, datasheet, and nameplate go to your engineering team for sign-off. Nothing enters production until you confirm the configuration is exactly what your project needs.
WE
Production Arrangement
Materials prepared, production slot scheduled, manufacturing kickoff. You receive a production timeline with key milestone dates so your project schedule stays predictable.
WE
Manufacturing & Assembly
Core assembly, winding, insulation processing, and active part assembly happen on schedule. Photo updates at each milestone available on request, so you can see your unit being built.
BOTH
Factory Testing
Routine tests run before shipment per IEC 60076. Test reports issued to you, and FAT or third-party witness can be arranged on request before the unit is released for packing.
WE
Packing & Shipment
Export packing prepared per your destination requirements, plus customs documents, packing list, certificate of origin, and shipping notification with tracking number.
BOTH
Installation & Technical Support
Installation manuals, operation guidance, and direct factory contact for any commissioning questions. You're not left alone once the truck arrives on site.
Frequently Asked Questions
Common questions from utility companies, EPC contractors, industrial facilities, and overseas transformer buyers. If your question isn't covered here, send your project requirements and we'll respond within 24 hours.
01 Are you a real oil-immersed transformer factory in China?
02 What types of oil-immersed transformers do you manufacture?
03 What information is required for quotation?
04 Can transformer specifications be customized?
05 Do you provide routine test reports before shipment?
06 Can customers witness factory testing?
07 How do you help reduce oil leakage risks?
08 Can transformers be used in high-temperature or outdoor environments?
09 What documents can you provide for projects?
10 What standards do your transformers comply with?
11 How long is the production lead time?
12 Do you provide technical support after delivery?
Send Your Project Requirements
Drop your specs or just a rough scope, Hank gets back to you personally within 24 hours with quotation, drawings, and a clear next step.
Hi, I'm Hank.
Your Transformer Project Contact
I read every message that comes through this form personally, no sales bots, no junior reps. Send me what you have and I'll come back with technical answers, not a brochure.
Even if you only have a single-line diagram or a rough scope, that's enough to start. We've helped utility companies, EPC contractors, and project engineers across 45+ countries turn rough requirements into delivered transformers, on spec, on time.
If you prefer WhatsApp or want to skip the form, my direct line is in the box. Either way, you reach me, not a queue.
Hank · ZOE Transformer
+86 153 0640 9721
Reply Time
Within 24 Hours
Tell Us About Your Project
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