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The 20MVA 33kV Three Phase Oil Immersed Power Transformer Dyn11 SZ-20000 is designed for reliable power transmission, distribution substations, and industrial power systems. With a rated capacity of 20MVA and a 33kV high-voltage rating, this transformer provides efficient and stable voltage transformation for medium- and high-voltage power networks.
The transformer adopts a three-phase oil immersed structure and Dyn11 vector group, providing effective insulation, heat dissipation, and reliable three-phase operation. Its robust tank, high-quality magnetic core, and optimized winding design help ensure stable performance under continuous operating conditions.
The SZ-20000 power transformer is suitable for utility substations, industrial facilities, power generation projects, and regional distribution networks. Customized voltage ratios, cooling configurations, tap changers, monitoring systems, and protection accessories can be provided according to project requirements. The transformer can be manufactured in accordance with applicable IEC standards and customer technical specifications.
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Sz-20000-33-11
Yawei
The SZ-20000kVA 33kV/11kV On-Load Tap Changer Power Transformer is a 20MVA three-phase oil immersed power transformer designed for reliable voltage transformation in substations, industrial power systems, commercial facilities, and renewable energy projects. Manufactured according to applicable IEC, IEEE, and GB standards, the transformer combines advanced core technology, robust winding construction, efficient cooling, and reliable insulation for long-term operation.
Key features include:
✔ 20MVA rated capacity for high-capacity power transmission and distribution
✔ 33kV/11kV voltage transformation for medium-voltage grid and industrial applications
✔ On-Load Tap Changer (OLTC) for voltage regulation without interrupting power supply
✔ Dyn11 vector group for reliable three-phase power system integration
✔ 8% impedance for improved short-circuit withstand capability
✔ ONAN/ONAF cooling for efficient thermal management under different load conditions
✔ High-quality grain-oriented silicon steel core for reduced losses and improved efficiency
Suitable for utility substations, industrial plants, commercial complexes, renewable energy projects, and regional distribution networks. Customized tap ranges, bushings, protection systems, monitoring devices, and cooling configurations are available according to project requirements.
The integrated On-Load Tap Changer (OLTC) allows the transformer to adjust the output voltage while remaining energized, helping maintain stable voltage under changing grid and load conditions. The flexible tap configuration can be customized according to system voltage requirements, making the transformer suitable for substations, industrial facilities, and renewable energy applications.
The transformer uses high-quality grain-oriented silicon steel and an optimized magnetic circuit design to reduce no-load losses and improve overall operating efficiency. Premium insulation materials and carefully designed winding structures provide reliable dielectric performance and help ensure stable operation throughout the transformer's service life.
The ONAN/ONAF cooling system provides effective heat dissipation under different operating loads. Natural oil circulation and air cooling provide efficient thermal management during normal operation, while forced air cooling can provide additional heat dissipation when the transformer operates under higher loads.
With an 8% impedance and reinforced winding structure, the SZ-20000kVA transformer is designed to withstand electrical and mechanical stresses caused by short-circuit conditions. The heavy-duty tank and robust construction provide reliable protection for the internal active components and support long-term operation in demanding power system environments.
Yawei provides customized solutions according to project specifications, including:
• ±9×1.67% on-load tap changer configuration
• Different high- and low-voltage bushing options
• ONAN/ONAF cooling configurations
• Temperature monitoring and protection systems
• Buchholz relay and pressure relief devices
• Online transformer condition monitoring
• SCADA-compatible monitoring solutions
• Customized anti-corrosion coatings for demanding environments
The SZ-20000kVA 33kV/11kV Power Transformer combines high capacity, stable voltage regulation, efficient cooling, and robust construction in a single power transmission solution. It is suitable for utility substations, industrial power networks, commercial infrastructure, renewable energy projects, and other applications requiring reliable 33kV-to-11kV voltage transformation.
Yawei provides complete technical documentation, factory testing, installation guidance, and customized engineering support to meet different international project requirements.
>> Technical Parameters
| Type | Step downpower transformer |
| Model | SZ-20000-33±9×1.67%/11 |
| Cooling Method | ONAN/ONAF |
| Primary Voltage | 33KV |
| Secondary Voltage | 11kV |
| Rated Frequency | 50HZ |
| Rated Power | 20MVA |
| Winding Material | Copper |
| Voltage Regulation | OLTC (On-Load Tap Changer) |
| Tapping Range | ±9×1.67% |
| Connection Group | YNd11 |
| Transformer Dimension | 6800×4500×5300 mm (approx.) |
| Weight | 42000 kg (approx.) |
Here are four specific application scenarios of the SZ-20000kVA 33kV/11kV Three Phase Oil Immersed Power Transformer:
The SZ-20000kVA 33kV/11kV power transformer is designed for primary substations and regional distribution networks, providing reliable voltage transformation from 33kV to 11kV. Its three-phase oil immersed construction, efficient cooling system, and robust insulation design support stable operation under continuous loads. The 8% impedance and Dyn11 vector group make it suitable for utility power networks, urban infrastructure, and medium-voltage distribution systems.
The transformer is suitable for solar power plants, wind farms, and other renewable energy projects requiring reliable grid connection and voltage transformation. The On-Load Tap Changer (OLTC) can regulate transformer voltage while the system remains energized, helping compensate for voltage fluctuations caused by changing generation and grid conditions. Its flexible configuration makes it suitable for renewable energy collection and grid interconnection systems.
Steel mills, cement plants, mining operations, petrochemical facilities, and other energy-intensive industries require stable and reliable power distribution. The SZ-20000kVA transformer provides efficient 33kV/11kV voltage transformation for industrial distribution networks. The ONAN/ONAF cooling system supports effective heat dissipation under varying loads, while the reinforced winding and tank structure provide reliable performance in demanding industrial environments.
The transformer can be deployed in large commercial and public infrastructure projects, including shopping centers, hospitals, airports, office complexes, and large industrial parks. It provides dependable medium-voltage power transformation and can be equipped with customized protection, monitoring, and cooling systems. Optional intelligent monitoring solutions enable real-time operating data collection, helping facility operators improve transformer maintenance and overall power system reliability.
General installation, commissioning, and maintenance guidelines for the SZ-20000kVA 33kV/11kV Three Phase Oil Immersed Power Transformer are provided below. All installation and commissioning work should be performed by qualified electrical technicians in accordance with the manufacturer's technical documentation and applicable safety standards.
Inspect the packaging before opening and use the designated lifting lugs and lifting equipment when handling the transformer. Keep the transformer properly balanced during lifting and avoid impact, excessive vibration, or mechanical stress to the tank and internal components.
Transport the transformer according to the manufacturer's handling requirements and keep the unit in the recommended position. After arrival, place it on a properly prepared foundation and ensure that the transformer is correctly aligned and securely positioned according to the approved installation drawings.
Inspect the transformer for transportation damage, oil leakage, deformation, loose components, and damaged bushings or accessories. Verify the nameplate information, accessories, spare parts, and technical documents against the packing list before installation.
If installation is delayed, store the transformer and its accessories in a clean, dry, and well-ventilated environment. Protect bushings, control equipment, and other sensitive components from moisture and contamination. Follow the manufacturer's instructions for oil preservation and nitrogen protection where applicable.
Install radiators, bushings, conservator equipment, valves, protection devices, and the OLTC mechanism according to the installation drawings. Check all connections carefully and tighten bolts and terminals to the specified torque. Operate the tap changer through its available positions to confirm smooth mechanical operation before commissioning.
For transformers requiring vacuum oil filling, carry out vacuum treatment and oil filling according to the manufacturer's specified procedures and parameters. Use qualified transformer insulating oil that meets the required technical standards. Ensure that the oil is properly filtered, degassed, and tested before filling.
Clean the transformer tank, bushings, radiators, and other external components after assembly. Repair any transportation-related coating damage and apply appropriate anti-corrosion protection where required, particularly for coastal, humid, or chemically aggressive environments.
Before energization, perform the required electrical and mechanical tests, including:
• Insulation resistance test
• Winding resistance test
• Transformer turns ratio test
• Vector group verification
• Insulating oil tests
• OLTC operation and transition tests
• Protection and alarm system checks
• Grounding and control circuit verification
All test results should comply with the applicable technical specifications and factory test requirements.
Before energization, confirm that all protection, grounding, cooling, monitoring, and control systems are correctly connected and operational. Energize the transformer according to the manufacturer's commissioning procedure and monitor voltage, current, oil temperature, winding temperature, noise, and abnormal indications. Load should be increased progressively while operating parameters remain within specified limits.
Regularly inspect oil level, oil temperature, winding temperature, cooling equipment, bushings, valves, grounding connections, and protection devices. Monitor the condition of insulating oil and perform dissolved gas analysis (DGA) when required. Periodically inspect the OLTC and carry out maintenance according to operating conditions, manufacturer's recommendations, and applicable maintenance standards.
Important: The above guide is intended as a general reference. Actual installation, oil filling, testing, commissioning, and maintenance procedures should always follow the manufacturer's official technical documents, drawings, factory test reports, and applicable local electrical safety regulations.
