In power systems, oil‑immersed transformers are the core equipment for voltage conversion and power distribution. Their selection and performance directly affect grid efficiency and operating costs. With China’s “dual carbon” goals and the implementation of the Transformer Energy Efficiency Improvement Plan, high‑efficiency, energy‑saving transformers have become the mainstream choice. Xinhong Electrical, as a professional power equipment supplier with years of experience in the transmission and distribution field, provides you with a comprehensive analysis of the technical features and selection criteria for the S13/11/0.4kV oil‑immersed transformer.
The S13 series oil‑immersed transformer is a new generation of energy‑efficient product developed by Xinhong Electrical based on the original S11 distribution transformer. Through independent innovation, technology introduction, and optimised design of the core and windings using new materials and processes, it achieves superior performance.
Take S13‑M‑800/10 as an example:
S – Three‑phase transformer
13 – Performance level code (higher numbers indicate better performance and lower losses)
M – Fully sealed construction
800 – Rated capacity (kVA)
10 – Voltage rating (kV)
The S13 series is currently a key promoted product in national power distribution equipment selection, offering outstanding energy savings. Compared with the S11 series, the no‑load loss of S13 transformers is reduced by about 30% on average, and load losses are also significantly decreased. All S13 products are manufactured using high‑permeability grain‑oriented silicon steel and advanced core technology. Both high‑ and low‑voltage windings can be supplied in copper or aluminium according to user requirements.
The core difference in S13 oil‑immersed transformers lies in the winding material: all‑copper transformers use pure copper windings, while aluminium‑wound transformers use pure aluminium. This is the root cause of all performance and price differences between the two types.
1. Superior Electrical Conductivity
Copper has only about 60% of the resistivity of aluminium. For the same capacity and performance requirements, copper‑wound transformers have lower operating losses and are more energy‑efficient over the long term. Both no‑load and load losses are lower than those of aluminium‑wound products.
2. Higher Mechanical Strength and Better Short‑Circuit Withstand Capability
Copper has far higher mechanical strength than aluminium and better heat resistance. This gives copper‑wound transformers superior thermal and dynamic stability under short‑circuit conditions. When a fault occurs in the distribution system, copper windings can withstand greater electromagnetic forces, ensuring equipment safety.
3. Longer Service Life and Lower Maintenance Costs
Copper is resistant to high temperatures, oxidation, and fatigue; it does not easily break or degrade. It offers strong overload capability and can adapt to complex outdoor conditions such as high temperature, heavy load, and extreme cold. All‑copper transformers can have a service life of 20–30 years – far longer than aluminium‑wound products – and require minimal maintenance over their lifetime.
4. Smaller Size and Lighter Weight (for the same rating)
For the same capacity and performance, copper‑wound transformers are smaller and lighter than aluminium‑wound ones – an important advantage where installation space is limited.
5. Higher Residual Value
Copper has good scrap value, so old equipment retains higher residual worth.
1. Obvious Cost Advantage
Aluminium is significantly cheaper. For the same model and capacity, an aluminium‑wound transformer costs much less – typically 20‑35% lower initial investment than the copper version.
2. Lighter Total Weight
Aluminium is less dense than copper, so aluminium‑wound transformers are lighter overall, making transport and installation easier.
3. Limitations
Aluminium has higher resistivity, leading to greater operating losses and higher long‑term energy consumption. It is also more prone to oxidation, fatigue, and overheating; under prolonged high‑load operation, it may suffer from oxidation, heating, or even breakage. Service life is typically only 8‑15 years. Moreover, aluminium windings have weak overload capacity and higher failure rates under frequent start‑stop or fluctuating load conditions.
Choose copper windings for: factory permanent power supply, residential community distribution, municipal grid upgrades, photovoltaic/wind renewable energy projects, hospitals/schools/public buildings, mining/chemical plants, and any high‑load or high‑reliability applications.
Consider aluminium windings for: short‑term temporary construction sites, rural temporary power, rental projects, or any use with a lifespan of only 3‑5 years.
Xinhong Electrical’s S13 series oil‑immersed transformers incorporate several advanced design technologies to ensure outstanding performance and reliability.
S13 transformers adopt a fully sealed design, eliminating the traditional conservator (oil expansion tank). The tank uses a corrugated‑fin construction, manufactured from high‑quality cold‑rolled steel sheets on a dedicated production line. The corrugated fins expand and contract with the thermal expansion and contraction of the transformer oil, completely isolating the internal oil from the atmosphere.
Advantages of this design:
Prevents and slows the deterioration of transformer oil and insulation moisture ingress
Enhances operational reliability with normal maintenance‑free operation
Effectively prevents oxygen and moisture from entering, which would degrade insulation performance
No oil replacement needed within the normal service life
The core is made of high‑quality, high‑permeability cold‑rolled grain‑oriented silicon steel (e.g., 0.23‑0.30mm Q‑series). It uses a multi‑step, stepped‑lap joint arrangement with fully mitered overlaps. This optimises the flux density distribution inside the core, reducing no‑load losses and noise.
According to GB/T6451‑2015, the S13‑M.RL series achieves a 50% average reduction in no‑load losses and a 30% reduction in load losses compared with the previous standard. Overall, S13 transformers offer 20‑30% lower no‑load loss than the national standard requirements.
Both high‑ and low‑voltage windings are wound using high‑quality electromagnetic wire:
High‑voltage windings: multi‑layer cylindrical construction, with well‑balanced ampere‑turn distribution, low leakage flux, high mechanical strength, and strong short‑circuit withstand capability.
Low‑voltage windings: for ratings up to 500kVA, double‑layer cylindrical; for 630kVA and above, foil‑wound construction.
Coils are wound with high‑strength enameled or paper‑covered copper/aluminium wire, with a well‑designed insulation structure.
The core and windings are each firmly secured; all fastening parts for leads and connections are equipped with self‑locking anti‑loosening nuts.
All internal fasteners use stop nuts to prevent loosening during transport and subsequent operation.
The design is “non‑lifting” – capable of withstanding transport vibrations.
The core and coils are vacuum‑dried; the oil is vacuum‑filtered and filled, minimising internal moisture.
The tank surface is phosphated and coated with three‑proof paint (moisture‑proof, mould‑proof, salt‑fog‑proof), suitable for humid and polluted environments such as metallurgical and petrochemical plants.
The transformer vector group is Dyn11, which effectively reduces harmonics in the grid and improves power quality. The Yyn0 vector group is also available upon request.
S13 series oil‑immersed transformers cover a capacity range of 30kVA to 2500kVA and voltage levels of 10kV and 35kV. Below are reference parameters for selected 10/0.4kV models:
| Model | Rated Capacity (kVA) | No‑load Loss (W) | Load Loss (W) | No‑load Current (%) | Short‑circuit Impedance (%) |
|---|---|---|---|---|---|
| S13‑M‑30 | 30 | 80 | 600/630 | 1.5 | 4.0 |
| S13‑M‑50 | 50 | 100 | 870/910 | 1.3 | 4.0 |
| S13‑M‑100 | 100 | 150 | 1500/1580 | 1.1 | 4.0 |
| S13‑M‑200 | 200 | 240 | 2600/2730 | 1.0 | 4.0 |
| S13‑M‑315 | 315 | 340 | 3650/3830 | 0.9 | 4.0 |
| S13‑M‑500 | 500 | 480 | 5100/5410 | 0.8 | 4.0 |
| S13‑M‑630 | 630 | 570 | 6200 | 0.6 | 4.5 |
| S13‑M‑800 | 800 | 700 | 7500 | 0.6 | 4.5 |
| S13‑M‑1000 | 1000 | 830 | 10300 | 0.6 | 4.5 |
| S13‑M‑1250 | 1250 | 970 | 12000 | 0.5 | 4.5 |
| S13‑M‑1600 | 1600 | 1170 | 14500 | 0.5 | 4.5 |
| S13‑M‑2000 | 2000 | 1550 | 18300 | 0.4 | 5.0 |
| S13‑M‑2500 | 2500 | 1830 | 21200 | 0.4 | 5.0 |
Note: Load loss values above the slash are for Dyn11 vector group, below the slash for Yyn0.
Choose the transformer capacity based on actual load calculations. Follow these steps:
Calculate total load: consider existing equipment, new production lines, and future expansion – sum up the total power demand.
Allow margin: select 1.2‑1.5 times the calculated load to avoid overloading or excessive no‑load losses due to oversizing.
Prefer energy‑efficient models: S13 series offers long‑term savings.
For long‑term, high‑reliability projects: choose copper windings. Higher initial cost pays back over a 20‑year lifecycle.
For short‑term or temporary projects: aluminium windings can help control upfront budget.
Dyn11: suppresses harmonics and improves power quality – recommended for locations with strict power quality requirements.
Yyn0: suitable for general distribution systems.
Standard service conditions for S13 series:
Ambient temperature: max +40°C, min ‑25°C
Altitude: <1000m
Installation site: free from fire/explosion hazards, heavy pollution, chemical corrosion, or severe vibration; both indoor and outdoor use are acceptable.
For special environments (high altitude, high humidity, salt fog, etc.), Xinhong Electrical offers customised designs.
Xinhong Electrical’s S13 series strictly complies with the following national standards:
GB/T 6451 – Technical parameters and requirements for three‑phase oil‑immersed power transformers
GB 1094.1‑2013 – Power transformers – Part 1: General
GB 1094.2‑2013 – Power transformers – Part 2: Temperature rise
GB 1094.3‑2017 – Power transformers – Part 3: Insulation levels, dielectric tests and external clearances
GB 1094.5‑2008 – Power transformers – Part 5: Ability to withstand short circuit
GB/T 15164 – Loading guide for oil‑immersed power transformers
GB 2536 – Transformer oils
Xinhong Electrical is committed to providing high‑quality power distribution solutions to customers worldwide. Our S13 series oil‑immersed transformers offer these core advantages:
Excellent energy efficiency: no‑load losses 20‑30% lower than national standard requirements
Fully sealed, maintenance‑free design: corrugated tank isolates oil from atmosphere, extending service life
Reliable short‑circuit strength: optimised winding and fastening ensure safety under sudden faults
Flexible customisation: copper/aluminium windings, various capacities, and vector groups available on request
Strict quality control: from raw material sourcing to final dispatch, every step meets national standards
For more product information or a customised solution, please contact the Xinhong Electricaltechnical team.
