These oil immersed transformers are designed for 10kV and 35kV power distribution systems, covering capacities from 30 kVA to 2500 kVA. Available in S11, S13, S20, and S22 series oil immersed distribution transformers that fully comply with GB/T 6451-2023 (technical parameters for oil-immersed power transformers) and GB 20052-2024 (energy efficiency limits and grades for power transformers). Whether you need a 100 kVA transformer for a residential grid, a 500 kVA distribution transformer for an industrial facility, or a 1000 kVA power transformer for a substation, production to your exact specifications.
Product Advantages
Moreover, manufactured in a 40,000 m² facility with over 100 sets of production and testing equipment. Therefore, below is the data — not claims, but verified numbers from third-party type test reports.
S20 Series: No-Load Loss Reduction by Up to 55% vs S11
For example, compared to the legacy S11 series still common in the market, the S20 series oil immersed distribution transformers cut no-load loss dramatically. Here is the head-to-head comparison at key capacities, measured per GB/T 6451-2023 test methods:
| Capacity (kVA) | S11 No-Load Loss (kW) | S20 No-Load Loss (kW) | Reduction | S11 Load Loss (kW) | S20 Load Loss (kW) | Reduction |
|---|---|---|---|---|---|---|
| 100 | 0.200 | 0.135 | 32.5% | 1.580 | 1.250 | 20.9% |
| 315 | 0.480 | 0.305 | 36.5% | 3.830 | 3.565 | 6.9% |
| 500 | 0.680 | 0.430 | 36.8% | 6.910 | 4.334 | 37.3% |
| 800 | 0.980 | 0.630 | 35.7% | 9.400 | 6.000 | 36.2% |
| 1000 | 1.150 | 0.745 | 35.2% | 11.500 | 8.240 | 28.3% |
| 1600 | 1.690 | 1.050 | 37.9% | 16.600 | 11.600 | 30.1% |
| 2500 | 2.360 | 1.440 | 39.0% | 23.200 | 14.840 | 36.0% |
Energy Efficiency & International Standards: The S20 series meets GB 20052-2024 Level 2, S22 series meets Level 1 (highest grade). GB 20052-2024 is China’s mandatory national standard (effective Feb 2025), aligned with IEC 60076-20 (international transformer energy efficiency standard). Additionally, products also comply with the IEC 60076 series — therefore suitable for global projects.
Complete S20-M Series Technical Parameters
The table below lists full specifications for the S20-M series oil immersed transformer, 10kV class, three-phase, with Dyn11 connection group. Specifically, all values are from third-party type test reports conducted per GB 1094.1-2013 and GB/T 6451-2023:
| Model | Capacity (kVA) | HV (kV) | LV (kV) | Connection | No-Load Loss (kW) | Load Loss (kW) | No-Load Current (%) | Impedance (%) |
|---|---|---|---|---|---|---|---|---|
| S20-M-30 | 30 | 6/10 | 0.4 | Dyn11 | 0.07 | 0.505 | 2.1 | 4.0 |
| S20-M-50 | 50 | 6/10 | 0.4 | Dyn11 | 0.09 | 0.730 | 2.0 | 4.0 |
| S20-M-100 | 100 | 6/10 | 0.4 | Dyn11 | 0.135 | 1.250 | 1.6 | 4.0 |
| S20-M-160 | 160 | 6/10 | 0.4 | Dyn11 | 0.18 | 1.850 | 1.4 | 4.0 |
| S20-M-200 | 200 | 6/10 | 0.4 | Dyn11 | 0.215 | 2.185 | 1.3 | 4.0 |
| S20-M-250 | 250 | 6/10 | 0.4 | Dyn11 | 0.26 | 2.900 | 1.2 | 4.0 |
| S20-M-315 | 315 | 6/10 | 0.4 | Dyn11 | 0.305 | 3.565 | 1.1 | 4.0 |
| S20-M-400 | 400 | 6/10 | 0.4 | Dyn11 | 0.37 | 3.815 | 1.0 | 4.0 |
| S20-M-500 | 500 | 6/10 | 0.4 | Dyn11 | 0.43 | 4.334 | 1.0 | 4.0 |
| S20-M-630 | 630 | 6/10 | 0.4 | Dyn11 | 0.51 | 4.960 | 0.9 | 4.5 |
| S20-M-800 | 800 | 6/10 | 0.4 | Dyn11 | 0.63 | 6.000 | 0.8 | 4.5 |
| S20-M-1000 | 1000 | 6/10 | 0.4 | Dyn11 | 0.745 | 8.240 | 0.7 | 4.5 |
| S20-M-1250 | 1250 | 6/10 | 0.4 | Dyn11 | 0.87 | 9.600 | 0.6 | 4.5 |
| S20-M-1600 | 1600 | 6/10 | 0.4 | Dyn11 | 1.05 | 11.600 | 0.6 | 4.5 |
| S20-M-2000 | 2000 | 6/10 | 0.4 | Dyn11 | 1.225 | 14.640 | 0.5 | 5.0 |
| S20-M-2500 | 2500 | 6/10 | 0.4 | Dyn11 | 1.44 | 14.840 | 0.4 | 5.0 |
Note: However, load loss values shown are for Dyn11 connection. Yyn0 connection values are slightly lower for capacities up to 500 kVA. Tap range: ±5% or ±2×2.5% (off-circuit tap changer).
Insulation Levels — Built for Harsh Environments
Furthermore, these oil immersed transformers are engineered with robust insulation systems tested to GB/T 311.1-2012 and GB/T 6451-2023 standards:
| Voltage Level (kV) | Max Operating Voltage (kV) | Power Frequency Withstand (kV/1min) | Lightning Impulse Full Wave (kV peak) | Lightning Impulse Chopped Wave (kV peak) |
|---|---|---|---|---|
| 0.4 | 0.69 | 3 | 75 | 85 |
| 10 | 12 | 35 | 75 | 85 |
| 20 | 23 | 55 | 125 | 140 |
| 35 | 40.5 | 85 | 200 | 220 |
Product Features
1. Fully Sealed Structure — Zero Maintenance
Because the transformer tank is fully welded and hermetically sealed (M-type design), the corrugated radiator wall expands and contracts with oil temperature changes, eliminating the need for a conservator tank on smaller units. Therefore, the sealed design isolates the insulation from oxygen and moisture.
Design Life: 20+ Years
Moreover, cellulose insulation thermal aging follows the 6°C rule per GB/T 1094.7-2024 (equivalent to IEC 60076-7) loading guide — design life of 20+ years, with no oil leakage, no moisture ingress, no scheduled maintenance.
2. Baosteel Hi-B Grain-Oriented Silicon Steel Core
Specifically, the core uses Baosteel high-permeability grain-oriented silicon steel (Hi-B type), thickness 0.27–0.30mm; S22 high-efficiency models use 0.23mm thin-gauge steel. Step-lap 45° joint construction reduces excitation current and core loss at the joints by 15-20% compared to conventional overlap joints.
Core Annealing & Winding Technology
Additionally, after stacking, the core undergoes annealing treatment to relieve internal stress from shearing and stacking, restoring magnetic path performance. Windings use parallel conductor transposition to reduce circulating current losses.
For reference, GB/T 6451-2023 reference no-load loss values for 1000 kVA: S11 1.150kW, S13 0.830kW, S20 0.745kW, S22 0.665kW. As a result, actual product values meet or beat the corresponding grade requirements.
3. Oxygen-Free Copper Windings with Dyn11 Connection
However, LV windings below 315 kVA use oxygen-free copper layer/cylinder construction. For 400 kVA and above, LV windings use copper foil construction for better short-circuit withstand and lower eddy current loss. Moreover, HV windings use multi-layer cylinder construction. The Dyn11 connection group suppresses triple harmonics, improves output voltage symmetry, and allows the neutral line to carry unbalanced load — therefore critical for power distribution transformer applications.
4. Low Noise Operation — 5-8 dB Below GB Standard Limits
Furthermore, core clamping uses steel tension bands instead of traditional bolted frames, reducing vibration transmission. Combined with the patented noise reduction device (spring-damper system + vacuum-sealed acoustic panels + sound-absorbing cotton), noise levels are 5-8 dB below GB standard sound power level limits. For example, comparison data:
| Capacity Range (kVA) | GB Standard Limit (dB) | Typical Value (dB) | Reduction |
|---|---|---|---|
| 30–63 | ≤44 | ≤38 | 6 dB |
| 80–100 | ≤48 | ≤41 | 7 dB |
| 125–160 | ≤49 | ≤42 | 7 dB |
| 200–250 | ≤51 | ≤44 | 7 dB |
| 315–400 | ≤53 | ≤46 | 7 dB |
| 500–630 | ≤54 | ≤47 | 7 dB |
| 800–1000 | ≤57 | ≤49 | 8 dB |
| 1250–1600 | ≤59 | ≤52 | 7 dB |
GB standard limits from GB/T 6451-2023 sound power level requirements. For reference, a 1000 kVA unit at ≤49 dB is comparable to normal conversation — suitable for residential installation.
5. Strong Short-Circuit Withstand Capability
In addition, the 35kV class transformers feature a rigid frame structure with upper beam and side beam tensioning, enhancing iron core clamping force. Because this design has been validated through short-circuit withstand testing per GB 1094.5, it demonstrates strong resistance to through-fault currents without winding deformation.
Patented Technologies
However, these products involve 4 dedicated patents specifically for oil immersed transformer design and manufacturing — each solving a real-world problem that generic manufacturers ignore. To clarify, here is what these patents mean for your project:
| Patent | Type | Problem Solved | Your Benefit |
|---|---|---|---|
| Transformer Noise Reduction Device | Utility Model | Traditional transformers transmit vibration to the tank, causing secondary noise | Patented spring-damper system absorbs vibration at the source. Noise drops 5-8 dB below GB standard limits. Quiet enough for residential installation. |
| Energy-Saving Automatic Oil Filling Device | Invention Patent | Manual oil filling leaves gap between filling and sealing, allowing dust contamination | Automated system fills and seals in one continuous operation. Zero dust ingress. Consistently high dielectric strength, extending insulation life by 3-5 years. |
| Adjustable Installation Position Transformer | Utility Model | Standard transformers have fixed brackets that only fit one orientation | 360° rotating base with adjustable brackets adapts to any site geometry. Cuts installation time by 40-60%. |
| Quick-Install Explosion-Proof Transformer | Utility Model | Pole-mounted transformers need 8-12 bolts, 2 workers, 30+ minutes | Spring-loaded locking hooks replace all bolts. One person installs in under 10 minutes. Reduces labor cost by 75%. |
Therefore, all patents are applied in production. The noise reduction device is built into every S20/S22 series tank. Moreover, the automatic oil filling system is used on 100% of the production line. The adjustable base and quick-install system are available as options for pole-mounted and explosion-proof configurations.
Application Scenarios for Oil Immersed Transformers
Scenario 1: Urban Residential Distribution Network
For example, a residential community of 500 households requires an 800 kVA distribution transformer stepping down 10kV to 0.4kV. The S20-M-800 delivers no-load loss of just 0.63 kW — compared to 0.98 kW for an S11 unit. At typical residential load patterns (average 35% utilization), this saves 3,066 kWh/year. Over a 20-year service life, that is 61,320 kWh in energy savings — equivalent to 61 tons of CO₂ reduction.
Scenario 2: Industrial Mining Enterprise Substation
Additionally, a mining operation needs a 35kV class power transformer reducing voltage from 35kV to 0.4kV for heavy equipment. Because the S11-1000/35 model (no-load loss 1.15 kW, load loss 11.5 kW, impedance 6.5%) handles the harsh environment with -25°C to +40°C operating range and robust short-circuit withstand, it is ideal for industrial use.
Scenario 3: Pole-Mounted Rural Electrification
However, for rural electrification projects requiring pole mounted transformers in the 15-167 kVA range, compact oil immersed transformers with sealed tank design are ideal. Specifically, the 100 kVA transformer model (S20-M-100) is lightweight enough for standard utility pole mounting, with no-load loss as low as 0.135 kW. Therefore, maintenance-free operation eliminates scheduled oil sampling in remote locations.
Scenario 4: Renewable Energy Grid Connection
Furthermore, solar farms and wind power plants require grid-connection transformers to connect to the 35kV distribution grid. The 35kV class oil immersed transformers with Dyn11 connection accommodate voltage fluctuations typical of intermittent renewable generation. Especially, the amorphous alloy transformer option (SH15 series) is perfectly suited for solar applications — ultra-low no-load loss of 0.06 kW at 100 kVA means minimal energy waste during idle periods.
Energy Efficiency Comparison: S11 vs S13 vs S20 vs S22 vs SH15
Therefore, choosing the right efficiency level depends on your load profile. Here is a decision framework based on GB 20052-2024 energy efficiency grades:
| Series | GB 20052-2024 Grade | 100 kVA No-Load Loss (kW) | 100 kVA Load Loss (kW) | Best For |
|---|---|---|---|---|
| S11 (old standard) | Below Level 3 (phased out) | 0.200 | 1.580 | Legacy units only — no longer legal for new procurement |
| S13 | Level 3 (minimum) | 0.150 | 1.580 | Budget projects, high load factor |
| S20 | Level 2 | 0.135 | 1.250 | Best balance of cost and efficiency |
| S22 | Level 1 | 0.110 | 1.100 | Maximum efficiency, premium projects |
| SH15 (Amorphous) | Level 1 | 0.060 | 1.270 | Light load, long idle hours |
Selection guide: If your transformer runs at above 60% average load, choose S22. However, if it runs at below 30% average load (typical for residential), choose SH15 amorphous core transformer. For everything in between, S20 is the optimal choice.
Quality Assurance
Moreover, every oil immersed transformer undergoes complete testing before shipment:
- Energy efficiency compliance: S20 meets GB 20052-2024 Level 2, S22 meets Level 1
- Third-party type test reports: Available for all series (S11, S13, S20, S22, SH15)
- Routine factory testing: No-load loss, load loss, impedance voltage, insulation resistance, oil BDV testing
- Quality management: Production follows ISO 9001 standards
- 4 product patents: Noise reduction, auto oil filling, adjustable base, quick-install explosion-proof
Therefore, technical datasheets and type test report references available with quotation.
Standards Compliance
Because international buyers require traceable standards, oil immersed transformers are designed, manufactured, and tested in accordance with:
- GB/T 1094.1-2013 — Power Transformers: General (equivalent to IEC 60076-1)
- GB/T 6451-2023 — Technical Parameters for Oil-Immersed Power Transformers
- GB 20052-2024 — Energy Efficiency Limits and Grades (mandatory, effective Feb 2025)
- GB/T 1094.7-2024 — Loading Guide (equivalent to IEC 60076-7)
- GB 2536-2025 — Transformer Oil / Mineral Insulating Oil
- IEC 60076 series — International power transformer standards
- IEC 60076-20 — International transformer energy efficiency standard
Available Capacities & Voltage Classes
Furthermore, we can supply multiple voltage grades and capacities for your different project requirements:
- 10kV class: 30, 50, 63, 80, 100, 125, 160, 200, 250, 315, 400, 500, 630, 800, 1000, 1250, 1600, 2000, 2500 kVA
- 20kV class: 30–2500 kVA
- 35kV class: 50–2500 kVA
- Connection groups: Dyn11 (standard), Yyn0 (optional)
- Tap changer: Off-circuit ±5% or ±2×2.5%; OLTC available for 35kV SZ series
- Cooling: ONAN (standard); ODAF available on request
Service Conditions
Meanwhile, please confirm site operating conditions before ordering:
- Ambient temperature: -25°C to +40°C
- Altitude: ≤1000m (derating available for higher altitudes)
- Maximum monthly average humidity: 90% (at 20°C)
- Indoor or outdoor installation
Ordering & Customization
Oil immersed distribution transformers available for export with these customization options. In case your site has special requirements, we can adjust design accordingly:
- Custom voltage ratios (e.g., 11kV to 380V, 13.8kV to 480V)
- Custom impedance values (4.0%–8.0%)
- Stainless steel tank for coastal/marine environments
- Silicone oil option for fire-resistant applications
- OLTC (on-load tap changer)
- Temperature monitoring devices
- Custom paint color and nameplate language
- Wooden case or steel crate export packaging
Therefore, send your required kVA rating, voltage ratio, and connection group — receive a detailed quotation within 24 hours.
Frequently Asked Questions
What is the difference between S11, S13, S20, and S22?
However, these series numbers represent efficiency levels defined by GB 20052-2024. S11 is the old standard (no longer legal for new procurement). S13 meets Level 3 (minimum, effective Feb 2025). S20 meets Level 2 with 10-20% lower loss than S13. S22 meets Level 1 (highest) with 20-28% lower total loss than S13. Therefore, the higher the number, the lower the losses, and the more energy saved over the 20+ year service life.
What does “oil immersed” mean?
An oil immersed transformer uses mineral insulating oil as both the insulating medium and cooling fluid. Specifically, the core and windings are submerged in oil inside a sealed steel tank. Heat transfers to the oil, which circulates through radiator fins for natural air cooling (ONAN). In comparison, this design offers superior insulation, efficient heat dissipation, and longer service life compared to dry type transformers.
How do I calculate the right kVA?
For three-phase: kVA = (Volts × Amps × 1.732) / 1000. For example, a 480V motor drawing 300A needs 250 kVA minimum. Additionally, add 20-30% margin for expansion. Engineering support available for transformer sizing — send load details.
Do you provide type test reports?
Yes. Third-party type test reports are available for each series (S11, S13, S20, S22, SH15). Moreover, routine test reports included with every shipment.
What is the lead time?
Standard models (30-2500 kVA, 10kV): 15-25 working days. However, 35kV class and custom: 25-40 working days.
Can you supply amorphous core transformers?
Yes. SH15 amorphous alloy transformers with no-load loss as low as 0.06 kW at 100 kVA — 70% lower than S11. As a result, ideal for residential distribution and solar grid connection.
What is the warranty period?
Standard warranty is 12 months from date of shipment. Moreover, fully sealed structure designed for 20+ years service life — maintenance-free, no oil change required.
Can you customize voltage ratios and impedance?
Yes. In addition, custom options include voltage ratios (11kV/380V, 13.8kV/480V, 35kV/0.69kV), impedance values (4.0%–8.0%), connection groups (Dyn11 standard, Yyn0 optional), and cooling method (ONAN standard, ODAF optional).
Related Products
Besides transformers, we also supply matching power equipment for full substation packages:
- Dry type transformers (SCB11/SCB13/SCB14/SCB18, 10kV/20kV/35kV, 30-2500 kVA)
- American pre-installed box-type substations (compact outdoor substation)
- HXGN15-12 high voltage switchgear (SF6 ring network units)
- Compact substations and unit substations
Contact Us for Your Transformer Project
Whether you need a single 15 kVA pole mounted transformer or a fleet of 2500 kVA substation transformers, delivered to your specifications. In short, send your requirements — capacity, voltage ratio, connection group, and quantity — and receive:
- Detailed quotation with FOB/CIF pricing
- Full technical datasheet and dimensional drawing
- Type test report reference
- Production timeline and shipping arrangement
Email: info@yujinmech.com
WhatsApp/WeChat: +86 13871337862
Website: yujinmech.com