Junray Electrical Oil-immersed Distribution Transformer — rated capacity from 100 kVA to 10,000 kVA, high voltage 10 kV or 35 kV, low voltage 0.4 kV. Features a corrugated sealed oil tank (leak-proof, maintenance-free), high-quality silicon steel core (15% lower loss than older models), off-load or on-load tap changing, and customizable copper or aluminum windings. Designed for outdoor installation in large factories, outdoor substations, large-scale PV plants, and major infrastructure projects. Capacity, voltage, impedance voltage, tap-changing method, and winding material can all be customized to match specific project requirements.
Boasting an exceptionally wide load capacity range—spanning from 100 kVA to 10,000 kVA—this transformer is perfectly suited to meet massive load demands, such as those found in the main power distribution systems of large-scale factories and major substations. It seamlessly handles the high-capacity requirements that dry-type transformers are unable to accommodate.
Offering a lower cost point compared to dry-type transformers, this solution delivers significant savings on equipment costs for large-scale power distribution projects. There is no need to incur the high expense of purchasing dry-type units; oil-immersed transformers suffice, thereby substantially reducing overall project costs.
Featuring robust weather resistance, the unit can be installed directly outdoors without fear of exposure to sun or rain. Its corrugated tank design incorporates a sealed structure that prevents oil leakage and protects against contamination, making Oil-immersed Distribution Transformer perfectly adapted to withstand harsh outdoor environments and eliminating the need to construct a dedicated indoor distribution room.
Utilizing a high-quality silicon steel core, the transformer exhibits extremely low power loss. Over the course of long-term operation, this translates into substantial savings on electricity bills, delivering significant energy-saving benefits—specifically, a 15% reduction in power loss compared to older-generation oil-immersed transformers.
Characterized by a low failure rate, Oil-immersed Distribution Transformer benefits from highly mature technology and stable operational performance. As a proven solution that has been utilized within the power distribution industry for decades, it offers convenient maintenance and is ideally suited for large-scale outdoor power distribution applications.
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Rated Capacity |
100KVA~10000KVA Customizable |
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Rated Voltage |
High Voltage: 10 kV/35KV; Low Voltage: 0.4 kV |
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Impedance Voltage |
4%~8% Customizable |
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Voltage Regulation Method |
Off-load Tap Changing / On-load Tap Changing |
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Transformer Winding Material |
Copper/Aluminum Customizable |
Standards & Compliance: This product is manufactured in strict compliance with applicable national standards for oil‑immersed distribution transformers. All quality control procedures and factory test methods follow the standard requirements for this product category. Detailed test reports and compliance documentation are available upon request.
1. Corrugated-Sealed Oil Tank: Features a corrugated-sealed tank design that prevents oil leakage, requires no maintenance, and eliminates the need for an external oil conservator.
2. Insulating Oil Cooling System: Utilizes insulating oil cooling to deliver powerful heat dissipation capabilities, making it suitable for handling high-capacity loads.
3. Off-Circuit Tap Changer: Equipped with an off-circuit tap changer that allows for the adjustment of the transformer ratio based on grid voltage fluctuations, ensuring compatibility with varying voltage levels.
4. Low-Loss Iron Core: Constructed with a high-quality silicon steel core that minimizes energy loss, thereby promoting energy efficiency and electricity savings.
5. Outdoor Protective Structure: Features a specialized protective enclosure designed for outdoor use, offering robust resistance against contamination and moisture to withstand harsh external environments.
Large-scale Factories: Outdoor power distribution and high-capacity loads for large industrial plants.
Outdoor Substations: Outdoor substations and high-capacity power distribution facilities.
Large-scale PV Systems: Outdoor transformers for large-scale photovoltaic power stations.
Major Infrastructure: Outdoor power distribution for major infrastructure projects.
We support flexible customization for this Oil‑immersed Distribution Transformer to match specific project requirements:
Rated Capacity: Adjustable within the 100 kVA to 10,000 kVA range
Rated Voltage: High voltage 10 kV or 35 kV; Low voltage 0.4 kV
Impedance Voltage: Customizable within 4% to 8%
Voltage Regulation Method: Off-load tap changing or on-load tap changing
Winding Material: Copper or aluminum
To discuss your specific project requirements, please contact our sales team with your load profile, installation conditions, and preferred delivery timeline.
Junray Electrical operates under a comprehensive quality management framework backed by multiple international and domestic certifications. For our Oil-immersed Distribution Transformer series, we emphasize not only routine quality control but also rigorous, transformer-specific testing to ensure long-term reliability in demanding outdoor power distribution applications.
ISO 9001 – Certified quality management system covering the entire production process, from raw material inspection to finished product testing, ensuring traceability and consistency across all transformer units.
CE – Products comply with essential EU safety, health, and environmental protection requirements, facilitating smooth customs clearance and market access for European projects.
CCC – China Compulsory Certification, mandatory for electrical equipment sold and installed within the Chinese domestic market.
CQC – China Quality Certification, verifying that our transformers meet national performance and safety standards for power distribution equipment.
CNAS – Our in-house testing laboratory is CNAS-accredited, validating our capability to conduct standard-compliant transformer tests including no-load loss, load loss, impedance voltage, and withstand voltage tests using calibrated equipment.
In addition to routine factory inspections, each Oil-immersed Distribution Transformer undergoes the following specialized tests in accordance with applicable national and international standards:
No-load loss and load loss measurement – to verify energy efficiency performance and confirm the 15% loss reduction compared to older-generation models.
Short-circuit impedance test – to ensure the impedance voltage falls within the guaranteed 4%-8% range.
Power frequency withstand voltage test – to validate insulation integrity and dielectric strength for 10kV/35kV systems.
Lightning impulse test (upon request) – to verify surge withstand capability for outdoor installations.
Sealing test – to confirm the corrugated oil tank integrity and guarantee zero oil leakage under pressure.
Oil quality test – to ensure the insulating oil meets dielectric strength and moisture content specifications.
Turns ratio test and vector group verification – to confirm correct transformer ratio and phase relationship.
Partial discharge test (upon request) – for applications requiring ultra-low partial discharge levels.
1.Question: What are the differences between oil-immersed distribution transformers and dry-type transformers?
Answer: The capacity of oil-immersed transformers can reach 100kva to 10,000kva, which can meet the needs of extremely large loads. However, the capacity of dry-type transformers is limited. At the same time, oil-immersed transformers are cheaper than dry-type transformers and can be directly placed outdoors without the need for an indoor distribution room, making them more suitable for large outdoor high-capacity distribution scenarios.
2. Question: Can this product be used directly outdoors?
Answer: We have adopted a corrugated sealed oil tank design, which has strong sealing performance. It can effectively prevent oil leakage and pollution. Combined with the outdoor-specific protective structure, it can prevent moisture, resist sunlight, rain and other elements. No additional protective facilities are required. It perfectly suits the harsh outdoor environment and does not need to build an indoor power distribution room separately.
3. Question: Can the capacity and voltage of the oil-immersed transformer be customized?
Answer: Oil-immersed Distribution Transformer has a rated capacity ranging from 100KVA to 10,000KVA, and a rated voltage covering high voltage 10kV/35kV and low voltage 0.4kV. At the same time, the impedance voltage, voltage regulation method, and winding material can all be customized. According to the outdoor power distribution requirements of different scenarios such as large factories and outdoor substations, we can tailor specific equipment to precisely meet the large-capacity outdoor power distribution needs.
4. Question: Where does the low-loss advantage of this product specifically lie?
Answer: We use high-quality silicon steel sheet cores, which have a loss rate 15% lower than that of the old oil-immersed transformers. The energy-saving effect is remarkable. Under long-term operation, it can significantly reduce electrical energy loss. The specific amount of electricity saved depends on the actual capacity and operating duration. The larger the capacity and the longer the operation time, the more electricity is saved, which can help large power distribution projects save long-term operation and maintenance costs.
As a professional manufacturer, we provide technical guidance to help overseas customers with proper product selection, installation preparation, and routine operation. Our team offers remote support during installation and commissioning. Spare parts are available for fast dispatch. For any technical inquiries, our team typically responds within 24 hours.
This project involves the construction of a new external power distribution system for a small-to-medium-sized manufacturing enterprise within an industrial park. The facility's primary loads consist of standard industrial inductive equipment—such as stamping machines, lathes, air compressors, fans, and pumps—characterized by frequent start-stop cycles, concentrated daytime loads, and light-load operation at night. The distribution transformer is located on a dedicated outdoor platform, offering ample space, excellent ventilation, and freedom from the fire safety restrictions associated with enclosed indoor areas.
Given the outdoor installation, cost-efficiency requirements, need for effective heat dissipation, and significant load fluctuations, the project utilizes an S13-M hermetically sealed oil-immersed power transformer rather than a dry-type unit. This single transformer serves as the main power source for the entire facility—covering motive power, lighting, and production equipment—thereby ensuring a stable, long-term power supply for operations.
Suitability of outdoor space for oil-immersed transformers: The outdoor transformer platform offers ample space and good ventilation, complying with installation standards without the strict fire safety constraints applicable to indoor installations.
Cost control: For the same capacity, oil-immersed transformers are significantly less expensive than dry-type transformers, substantially reducing the enterprise's infrastructure investment.
High heat dissipation requirements: With concentrated industrial equipment, heavy daytime loads, and rapid temperature rises, the self-cooling oil circulation system of oil-immersed transformers outperforms dry-type units, making them ideal for continuous heavy-load operation.
Robust overload and surge resistance: Workshop machinery creates significant surge loads during startup and shutdown; oil-immersed transformers offer superior short-circuit and overload resilience, making them well-suited for fluctuating industrial loads.
Simple, mature maintenance: Oil-immersed transformers feature a simple structure, making fault diagnosis and repair straightforward and allowing for the use of standard spare parts—ideal for the facility's routine maintenance capabilities. Equipment Configuration
Based on the calculated total load, an S13-M-800kVA 10kV/0.4kV hermetically sealed, energy-efficient oil-immersed transformer is installed on the outdoor platform. It features a hermetically sealed corrugated tank design without an oil conservator, making it suitable for all-weather outdoor operation.
Model: S13-M-800kVA Fully Sealed Oil-Immersed Power Transformer
Rated Voltage: 10±2×2.5% / 0.4kV
Cooling Method: Oil-immersed self-cooling (ONAN)
Core Material: High-permeability silicon steel sheets; low-loss, energy-efficient structure
Structural Features: Fully sealed corrugated oil tank; maintenance-free; oxidation and moisture resistant; stable insulation performance
Protection Configuration: High-voltage drop-out fuse, lightning arrester, low-voltage main switch, grounding protection
Installation Method: Outdoor overhead installation on a steel platform; includes lightning protection, grounding, and safety fencing
Ultra-low loss and high energy efficiency: Features the S13 energy-saving structure; no-load and load losses are significantly lower than older S11 and S9 models, resulting in substantial long-term electricity cost savings.
Excellent outdoor adaptability: The fully sealed structure isolates the unit from air, rain, and dust; resistant to condensation and oxidation; suitable for outdoor operation in both high summer temperatures and low winter temperatures.
Superior heat dissipation: Uniform heat dissipation via transformer oil circulation ensures stable temperature rise under heavy loads, avoiding the high-temperature load-limiting issues common in dry-type transformers.
High impact and short-circuit resistance: Stable operation under the shock loads caused by frequent starting and stopping of industrial motors; resistant to overheating and tripping.
Clear cost-performance advantage: Low equipment cost, simple installation, and no need for complex fire-suppression facilities, significantly reducing the cost of factory power distribution infrastructure.
Stable and compliant power supply quality: Post-commissioning voltage deviation and three-phase balance fully meet industrial power standards, ensuring smooth operation of workshop equipment.
No anomalies under peak loads: Transformer oil temperature and temperature rise remain normal during full-load daytime production; no overloading or abnormal heating occurs.
Significant energy and loss reduction: Low-loss core design drastically cuts transformer losses, effectively reducing the enterprise's monthly basic electricity charges and loss-related costs.
Zero-fault outdoor operation: The fully sealed structure eliminates risks of water ingress, moisture, and corrosion, ensuring stable, all-weather operation throughout the year. Convenient and Low-Cost O&M: The equipment features a mature design and a low failure rate; routine maintenance requires only visual inspections and checks of oil levels and grounding, resulting in minimal operational burden.
Oil-immersed transformers (S13-M series) are the preferred choice for power distribution projects in industrial plants, rural distribution areas, external grid substations, and open-site installations. Compared to dry-type transformers, they offer advantages such as superior heat dissipation, high overload and impact resistance, lower costs, excellent energy efficiency, and ease of maintenance. They are particularly well-suited for outdoor installation and industrial applications characterized by significant load fluctuations or heavy loads, representing the most mature and cost-effective transformer solution for external grid distribution projects.
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