Outdoor transformer box delivering safe, reliable, and efficient medium-voltage power distribution for modern utility and industrial networks
01 General
1.1 Project Description
In 2025, an American customer placed an order for a 2660 kVA three phase pad mounted transformer, designed for installation within a medium voltage distribution transformer network in the United States, where reliability, safety, and long-term operational performance were essential for the project’s power infrastructure. The transformer functions as an outdoor transformer box, integrating the transformer tank, switching equipment, protection devices, and electrical connection components within a compact pad-mounted enclosure suitable for utility distribution networks and industrial environments. Additionally, as part of the same order, the customer procured a smaller 150 kVA pad mounted transformer to supply auxiliary loads within the project’s electrical system.
The unit is rated at 2660 kVA, with a primary voltage of 22.8 kV and secondary voltage of 0.8 kV, and uses the YNd1 vector group, which supports stable three-phase voltage transformation; proper phase displacement and grounding characteristics are maintained, as required for medium voltage distribution transformer systems. This configuration steps down utility medium-voltage power efficiently, while delivering consistent voltage to downstream electrical loads-reliable, stable, and ready for grid integration.
Designed and manufactured in accordance with IEEE Std C57.12.34-2022, the transformer complies with North American standards for pad mounted transformer equipment, ensuring safe operation in underground distribution systems and outdoor installations where environmental exposure and operational safety must be carefully controlled.
1.2 Technical Specification
1.2 Technical Specification
2660kVA three phase pad mounted transformer specification and data sheet
| Delivered to | America |
| Year | 2025 |
| Type | Three phase pad mount transformer |
| Standard | IEEE Std C57.12.34-2022 |
| Rated Power | 2660KVA |
| Frequency | 60HZ |
| Feed | Loop |
| Front | Dead |
| Phase | three |
| Cooling Type | KNAN |
| Liquid insulant | FR3 Oil |
| Primary Voltage | 22.8 kV |
| Secondary Voltage | 0.8 kV |
| Vector Group | YNd1 |
| Winding Material | Aluminum |
| Impedance | 5.75% |
| Efficiency | DOE |
| Tap Changer | NLTC |
| Tapping Range | ±2*2.5% |
| No Load Loss | 2.5 kV |
| On Load Loss | 16.5 kV |
| Accessories | Grounded shield |
1.3 Drawings
2660kVA three phase pad mounted transformer drawing and nameplate
02 Manufacturing
2.1 Tank
The pad-mounted transformer tank is a fully welded, sealed structure, built to be durable and tamper-resistant, suitable for outdoor installations. Doors are secured with penta bolts and 3-point vault locks; the powder-coated white finish (RAL 9003) provides resistance against environmental exposure, corrosion, and UV degradation.
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2.2 Insulation System
 | The transformer employs FR3 natural ester insulation fluid. Primary and secondary windings are aluminum and insulated to withstand both phase-to-phase and phase-to-ground voltage stresses. Additionally, the unit features a grounded electrostatic shield between primary and secondary windings, which reduces high-frequency interference and voltage surges. |
03 Monitoring And Protection System
3.1 Electrical Protection and Monitoring
To ensure safe and reliable operation, the medium voltage distribution transformer is equipped with multiple monitoring and protection components integrated within the outdoor transformer box enclosure. Key features include: • Grounded electrostatic shield
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| Device | Function |
| Oil Level Gauge | Monitors insulation oil level |
| Oil Temperature Gauge | Monitors transformer operating temperature |
| Tank Pressure Gauge | Detects internal pressure changes |
| Pressure Relief Valve | Protects against excessive internal pressure |
These monitoring instruments provide continuous operational visibility, allowing maintenance teams to identify potential issues before they evolve into operational failures. Preventive monitoring enhances reliability and ensures long-term stability of medium voltage distribution transformer networks. Additionally, operators can react quickly to abnormal conditions, reducing downtime.
3.2 Switching and Protection Components
 | The transformer supports coordination with customer-supplied external protection devices, including Eaton Bussmann High-Speed Fuse 170M series, designed to provide rapid response to electrical faults. The unit includes: • Three two-position load break switches This arrangement allows the three phase pad mounted transformer to safely isolate electrical faults while maintaining continuity for the remainder of the distribution network. Coordinated switching and protection ensure fast fault response, reliable system protection, and uninterrupted power delivery, making the outdoor transformer box highly suitable for utility-scale and industrial solar PV applications. |
04 Testing
05 Packing and transportation
06 Typical Applications
As an outdoor transformer box, this pad mounted transformer is designed for installation in a wide range of medium voltage distribution transformer environments, including industrial power systems, utility infrastructure, renewable energy facilities, and commercial distribution networks where safe outdoor transformer installation is required.
Typical applications include:
• Utility medium-voltage distribution systems
• Industrial power distribution
• Renewable energy facilities, including solar PV farms
• Infrastructure and commercial projects
In these environments, the transformer provides efficient voltage conversion while maintaining high operational reliability, also enabling easy integration with auxiliary transformer box electrical units.
07 Site and Summary
Within the overall electrical infrastructure of the project, the 2660 kVA outdoor transformer box serves as the primary medium voltage distribution transformer, converting utility medium-voltage power into a usable voltage level for downstream electrical systems while ensuring safe and stable operation through its IEEE-compliant design, FR3 insulation system, and integrated protection equipment. The transformer forms the central power conversion unit within the project’s distribution network, also working in coordination with the 150 kVA auxiliary transformer box electrical unit to ensure reliable, continuous power supply.
