Basic information
Type: Oil Immersed Transformer
Phase: Three
Service Voltage: up to 35KV
Rated Capacity: up to 31500kVA
Vector group: Dyn11
Cooling type: ONAN
Core material: CRGO
Winding material: Copper/aluminum
Available fluids: mineral oil and ester fluids
Purpose:Three-phase oil filled pad mounted electrical transformers are intended for transforming of electric energy in networks of power systems and in energy consumer networks.
Product Overview
The Tianya Electric 35kV oil immersed transformer is engineered for reliable voltage conversion in substations, industrial power systems, mining facilities, renewable-energy projects and utility distribution networks. Available from 630 kVA to 31,500 kVA, Oil Immersed Transformers can be configured around the required voltage ratio, loss level, tapping method, winding material, insulating fluid and site conditions.
Unlike a catalogue-only supply, Tianya Electric controls the core, winding, tank, active-part assembly, vacuum processing and final testing within its own production chain. This gives EPC contractors, utilities and industrial buyers one technical interface from specification review to factory acceptance and shipment.
Product Structure
The full inclined step joint design optimizes the flux path, eliminating local flux saturation at the core joints, thereby reducing no-load losses and currents while minimizing transformer noise. To enhance short-circuit resistance, pressure nails are strategically placed around the pressure plates, and support beams connect the upper and lower high and low voltage clips, ensuring the core remains structurally intact. Additionally, the core column surface is coated with specialized end face adhesive for silicon steel sheet , bonding the sheets together and solidifying the core into a single unit after curing. High-strength electrical laminated wood supports are used between the lower part of the body and the tank wall, ensuring reliable positioning of the lower section.
Quality Assurance: Every 35kV transformer undergoes full-load test, insulation resistance, dielectric test, and noise level verification. Factory Acceptance Test (FAT) reports are provided for international projects.
After-Sales Support: Our global service team provides installation guidance, technical support, and spare parts supply, ensuring project uptime and operational safety.
Standards:
● GB1094.1-1996
● GB1094.3-2003
● GB/T6451-200
Parameters
| 35kV Oil-immersed Three-phase Doubl- winding Non-excited Voltage Regulation Distribution Transformer Parameters | ||||||||
| Rated Power (kVA) | Vector group | Efficiency Level 1 | Efficiency Level 2 | Efficiency Level 3 | Short Circuit Resistance% | |||
| No-load Loss (kW) | On-load Loss (75℃ kW) | No-load Loss (kW) | On-load Loss (75℃ kW) | No-load Loss (kW) | On-load Loss (75℃ kW) | |||
| 3150 | YNd11 | 1.7 | 20.7 | 2.0 | 20.7 | 2.4 | 21.9 | 7 |
| 4000 | 2.0 | 24.6 | 2.3 | 24.6 | 2.9 | 25.9 | ||
| 5000 | 2.4 | 28.2 | 2.8 | 28.2 | 3.5 | 29.7 | ||
| 6300 | 2.9 | 31.5 | 3.4 | 31.5 | 4.2 | 33.3 | 8 | |
| 8000 | 4.0 | 34.6 | 4.7 | 34.6 | 5.8 | 36.5 | ||
| 10000 | 4.8 | 40.8 | 5.7 | 40.8 | 7.0 | 43.0 | ||
| 12500 | 5.5 | 48.4 | 6.5 | 48.4 | 8.0 | 51.1 | ||
| 16000 | 6.7 | 59.2 | 7.9 | 59.2 | 9.7 | 62.5 | ||
| 20000 | 7.9 | 71.6 | 9.4 | 71.6 | 11.5 | 75.5 | ||
| 25000 | 9.4 | 84.6 | 11.1 | 84.6 | 13.6 | 89.3 | 10 | |
| 31500 | 11.1 | 100.8 | 13.1 | 100.8 | 16.2 | 106.4 | ||
● Energy Efficiency
The 35kV oil-immersed transformer for sale incorporates advanced energy-saving technology, effectively reducing energy consumption and improving efficiency. The core is constructed from high-quality cold-rolled silicon steel sheets, characterized by low loss, low noise, and high efficiency.
● Low Noise
Utilizing high-quality windings and high-performance materials, the transformer operates with minimal noise. Its robust insulation system and reliable structural design ensure stable long-term operation, further reducing possibility of generating noise.
●High Reliability
The core is made from specially treated, low-loss, low-noise steel, providing excellent corrosion and heat resistance. This allows for reliable operation under harsh environmental conditions. High-quality materials and precise manufacturing ensure the transformer's reliability and longevity.
● Ease of Maintenance
The transformer's design facilitates easy maintenance and repair. An automatic protection system automatically disconnects the power supply in case of faults, preventing potential short circuits and fires caused by damaged components. Simple operations allow maintenance personnel to efficiently service the transformer, enhancing its usability.
● The transformer core is made of high magnetic conductivity, grain-oriented cold-rolled silicon steel sheets, ensuring low no-load loss.
● The three-phase windings use concentric coils with corrugated oil ducts. A non-dipping paint process and tight band binding enhance mechanical strength, ensure balanced ampere-turn distribution, and provide excellent short-circuit resistance.
● To prevent displacement during transportation, a positioning structure is added to the core assembly. All fasteners are secured with locking nuts to avoid loosening during long-term operation.
● The voltage transformer adopts a fully sealed design. Vacuum oil filling completely removes internal moisture, isolates the oil from ambient air, prevents oil aging, and improves operational reliability. Pressure relief valves are installed across all capacity sections, and optional gas relays with alarm and trip functions are available for enhanced safety.
● A corrugated oil tank design offers simple manufacturing, high strength, excellent welding performance, and no leakage. The strong oil fluidity also improves heat dissipation.
● Compact, aesthetically pleasing, and space-saving, this transformer is an ideal maintenance-free solution.
Rich Manufacturing Legacy
Operating since 2007 with a full end-to-end production setup and 6,000 m² facility.
Strict Quality Governance
Multi-stage QC—from supplier approval to pre-shipment testing—ensures 100% defect-free deliveries.
Deep Technical Expertise
A team of 30+ seasoned engineers deliver tailored engineering, site support, and seamless product integration.
Comprehensive Manufacturing Process
In‑house iron core, coils, oil tanks, assembly, vacuum-drying, testing, and packaging—all under one roof for maximal control.
Lifetime Support & After‑Sales
24/7 customer service, technical assistance, rapid spares, renovation, and maintenance available internationally.
Custom Solution Design – Voltage, power ratings, cooling methods, accessories, oil types tailored per project.
Technical & Project Consulting – EMC assessments, tap changer planning, loading optimization.
Factory Acceptance Tests – Witnessed dry and wet tests to international ANSI/IEC standards.
International Logistics & Support – Global delivery, customs clearance, and on-site commissioning.
After‑Sales Maintenance – Spare parts supply, oil analysis, refurbishment, and comprehensive troubleshooting.
The following configuration defines the standard product platform. Final values are confirmed against the approved technical data sheet because the voltage ratio, tap range, impedance, losses, accessories and service environment affect the completed design.
| Item | Standard / Available Configuration | Buyer Relevance |
|---|---|---|
| Product type | Three-phase, two-winding oil immersed transformer | For medium-voltage power transformation and distribution |
| Rated capacity | 630–31,500 kVA | Selected from the calculated load, growth allowance and redundancy plan |
| High-voltage class | Up to 35 kV | Voltage ratio and insulation level are matched to the project network |
| Vector group | Dyn11 or YNd11; other groups by engineering review | Must coordinate with grounding, protection and parallel-operation requirements |
| Cooling | ONAN standard | Uses natural circulation of oil and air for dependable heat dissipation |
| Core material | CRGO electrical steel | Supports low no-load loss and controlled operating noise |
| Winding material | Copper or aluminum | Chosen according to loss target, budget, dimensions and project specification |
| Insulating fluid | Mineral oil or ester fluid | Selected around fire safety, environmental and operating requirements |
| Voltage regulation | Off-circuit or on-load arrangement according to project requirements | Matches the permitted voltage variation and operating strategy |
| Reference standards | IEC 60076, GB 1094 and GB/T 6451 | Destination-country and purchaser specifications are reviewed before design release |
These values are selection references for 35kV three-phase, two-winding, non-excitation voltage-regulating transformers. Confirm the applicable efficiency level and guaranteed values in the final quotation.
| Rated Power (kVA) | Vector Group | Efficiency Level 1 | Efficiency Level 2 | Efficiency Level 3 | Short-Circuit Impedance (%) | |||
|---|---|---|---|---|---|---|---|---|
| No-Load Loss (kW) | Load Loss at 75°C (kW) | No-Load Loss (kW) | Load Loss at 75°C (kW) | No-Load Loss (kW) | Load Loss at 75°C (kW) | |||
| 3,150 | YNd11 | 1.7 | 20.7 | 2.0 | 20.7 | 2.4 | 21.9 | 7 |
| 4,000 | YNd11 | 2.0 | 24.6 | 2.3 | 24.6 | 2.9 | 25.9 | 7 |
| 5,000 | YNd11 | 2.4 | 28.2 | 2.8 | 28.2 | 3.5 | 29.7 | 7 |
| 6,300 | YNd11 | 2.9 | 31.5 | 3.4 | 31.5 | 4.2 | 33.3 | 8 |
| 8,000 | YNd11 | 4.0 | 34.6 | 4.7 | 34.6 | 5.8 | 36.5 | 8 |
| 10,000 | YNd11 | 4.8 | 40.8 | 5.7 | 40.8 | 7.0 | 43.0 | 8 |
| 12,500 | YNd11 | 5.5 | 48.4 | 6.5 | 48.4 | 8.0 | 51.1 | 8 |
| 16,000 | YNd11 | 6.7 | 59.2 | 7.9 | 59.2 | 9.7 | 62.5 | 8 |
| 20,000 | YNd11 | 7.9 | 71.6 | 9.4 | 71.6 | 11.5 | 75.5 | 8 |
| 25,000 | YNd11 | 9.4 | 84.6 | 11.1 | 84.6 | 13.6 | 89.3 | 10 |
| 31,500 | YNd11 | 11.1 | 100.8 | 13.1 | 100.8 | 16.2 | 106.4 | 10 |
Note: The table is for preliminary selection only. Guaranteed losses, impedance, dimensions, weight, temperature rise and insulation level are subject to the approved project-specific technical schedule.
The multi-step, fully inclined core joint creates a controlled magnetic path and helps limit local flux concentration. Tianya Electric uses grain-oriented silicon steel sourced from established mills such as Shougang and Baosteel, without refurbished or spliced material. Precision cutting, stacking and clamping support lower no-load loss, current and audible noise.
Concentric three-phase windings, balanced ampere-turn distribution, oil ducts and reinforced axial clamping improve thermal performance and mechanical stability. Pressure elements and upper-to-lower support structures help the active part resist movement during transport and electrodynamic stress during a system fault.
The active part is vacuum dried and the insulating fluid is vacuum filled to reduce retained moisture. This protects dielectric performance and helps slow oil and cellulose insulation ageing during long-term service.
Corrugated or folded tank structures provide mechanical strength and effective heat-transfer area while reducing unnecessary welds. For ratings above 6,300 kVA, the folded tank approach also improves structural integrity. Sealing surfaces and weld quality are checked before shipment to reduce leakage risk.
Because transformer performance begins with the magnetic circuit, you can also review our oil immersed transformer core manufacturing capability.
A 35kV transformer should not be selected by capacity alone. Our engineering team checks system voltage, load profile, impedance coordination, protection philosophy, installation environment and applicable standards before releasing the design.
Rated capacity, HV/LV ratio, frequency, vector group, impedance, insulation level, loss target and tap range.
Copper or aluminum windings, mineral or ester fluid, ONAN cooling and engineered alternatives where the rating or site requires them.
Pressure relief valve, gas relay, temperature indication, oil-level monitoring, surge protection interfaces and customer-specified terminals.
Tank structure, bushing position, cable-box interface, lifting and jacking provisions, wheels, earthing terminals, coating and colour.
Outdoor duty, high altitude, high or low ambient temperature, humidity, pollution, corrosive atmosphere and seismic conditions.
Technical data sheet, general arrangement drawing, nameplate drawing, test report, operation manual and packing documentation as agreed.
Engineers review the single-line data, load, voltage regulation, accessories, standards and site conditions before quotation and design approval.
Material verification is followed by checks during core fabrication, winding, insulation assembly, tank production, drying and oil filling.
Applicable routine tests are completed before release. Test results can be compiled in a FAT report, with customer or third-party witness arrangements agreed at order stage.
The completed unit is inspected, protected for the agreed transport method and supplied with the contracted drawings, reports and operating documents.
Winding resistance measurement
Voltage ratio and vector-group verification
No-load loss and no-load current measurement
Load loss and short-circuit impedance measurement
Applied and induced voltage withstand tests
Insulation and oil-related checks as applicable
Tank sealing and accessory function inspection
Type or special tests, including temperature-rise and impulse tests, are arranged when required by the specification or contract.
Step-down service in urban and regional networks where predictable losses, coordinated impedance and reliable outdoor operation are essential.
Primary distribution for process plants, mines, cement facilities, steel production and other sites with concentrated or continuously changing loads.
Voltage transformation for renewable-energy collection and grid-connection systems, configured to the project voltage and operating profile.
Project-specific configurations for demanding outdoor environments, with coating, accessories and protection interfaces selected during technical review.
Distribution for transport, water treatment, municipal facilities and large commercial or public projects requiring stable medium-voltage supply.
Dimension, impedance, terminal arrangement and accessory matching for replacement of ageing transformers or expansion of an existing substation.
For alternative voltage and efficiency configurations, browse our complete oil immersed transformer range.
Tianya Electric developed from a transformer-core factory into an integrated transformer manufacturer. The company reports a 20,000 m² site, more than 150 employees, over 30 technical specialists and annual production capacity exceeding 6,000 units.
Core cutting and stacking, winding, tank fabrication, assembly, vacuum processing, testing and packing are coordinated in-house. This reduces hand-off risk and makes technical changes easier to control.
Production operates under ISO 9001 quality management. Designs are developed against IEC 60076 and relevant GB standards, while destination-country requirements are reviewed for each contract.
Our team supports specification review, transformer selection, drawings, FAT coordination, export documentation, commissioning guidance and after-sales troubleshooting.
Please provide rated capacity, HV and LV voltage, frequency, phase, vector group, tap range and method, impedance, winding material, insulating fluid, cooling method, applicable standard, accessories, maximum ambient temperature, altitude, installation environment, quantity and destination. A single-line diagram or purchaser specification is especially helpful.
Yes. The 35kV platform can be engineered around the required secondary voltage, vector group, tap arrangement and insulation level after the network data and applicable standard have been reviewed.
An off-circuit tap changer is suitable when adjustment can be made with the transformer de-energized. An on-load tap changer is preferred where the output voltage must be regulated while the transformer remains in service. The final choice depends on network fluctuation, operating procedure, control requirements and budget.
Yes. Copper or aluminum windings and mineral or ester fluid can be specified. The engineering and commercial proposal will reflect the required losses, fire-safety objectives, environmental conditions and total project cost.
Yes, subject to engineering review. Altitude and ambient temperature affect insulation coordination, clearances, temperature rise and cooling performance, so these conditions must be declared before design approval.
The agreed document package can include an approved technical data sheet, general arrangement and nameplate drawings, routine test report, operation and maintenance manual, packing list and supporting compliance documents required by the contract.
Send your voltage ratio, capacity, tap requirement, impedance, loss target, service conditions, accessories, quantity and destination. The Tianya Electric engineering team will review the data and prepare a technical and commercial proposal for your project.
Request a Quote35KV Oil Immersed Transformer Purpose
Three-phase oil filled pad mounted electrical transformers are intended for transforming of electric energy in networks of power systems and in energy consumer networks.
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