Engineered underground transformers delivering safe, efficient, and reliable power distribution for modern utility and renewable energy networks
01 General
1.1 Project Description
In 2026, a Canadian customer ordered two 2000kVA three phase pad mounted transformers for underground utility distribution applications. The project required high-efficiency underground transformers compliant with CSA C802.1 and CSA C227.4 standards, with particular emphasis on energy-loss control, outdoor reliability, and utility-grade operational safety.
The underground transformers are configured with 25kV primary voltage and 600Y/347V secondary voltage using a Dyn1 vector group, making them suitable for loop-feed underground distribution systems commonly used in North America. Both HV and LV windings utilize aluminum conductors, while the ONAN mineral-oil cooling system supports stable long-term outdoor operation under utility loading conditions.
The customer also specified strict efficiency requirements, including a minimum efficiency of 99.37%, controlled no-load and load losses, dead-front safety construction, and complete protection accessories for underground power distribution systems.
1.2 Technical Specification
2000 kVA underground transformers specification and data sheet
| Delivered to | Canada |
| Year | 2026 |
| Type | Three phase pad mount transformer |
| Standard | CSA C802.1 |
| Rated Power | 2000KVA |
| Frequency | 60HZ |
| Feed | Loop |
| Front | Dead |
| Phase | three |
| Cooling Type | ONAN |
| Liquid insulant | Mineral Oil |
| Primary Voltage | 25 kV |
| Secondary Voltage | 0.6 kV |
| Vector Group | Dyn1 |
| Winding Material | Aluminum |
| Impedance | 5.75% |
| Efficiency and Losses Standard | CSA C802.1-13 99.37% |
| Tap Changer | NLTC |
| Tapping Range | ±2*2.5% |
| No Load Loss | 2,220 W |
| On Load Loss | 18,300 W |
| Accessories | Standard Configuration |
1.3 Drawings
2000 kVA underground transformers drawing and nameplate
02 Manufacturing
2.1 Core
The pad mounted transformer adopts a low-loss core structure optimized for CSA efficiency requirements and long-term underground utility operation. The magnetic circuit design helps reduce no-load losses, localized heating, and operating noise while supporting the project’s strict 99.37% minimum efficiency target.
2.2 Winding
 | The underground transformer utilizes a Dyn1 vector group with delta-connected HV winding and grounded-wye LV winding, a configuration widely used in underground distribution systems because it improves harmonic tolerance, stabilizes neutral operation, and enhances overall distribution reliability. Both HV and LV windings use aluminum conductors to provide stable thermal performance, lower transformer weight, and cost-effective long-term utility operation. |
2.3 Tank
The pad mounted transformer adopts a dead-front utility-grade enclosure suitable for public outdoor installation, with fully insulated live parts to improve operational safety during cable connection and maintenance. The transformer tank utilizes fully welded sealed construction to reduce moisture ingress and oil oxidation, helping extend insulation life during long-term outdoor operation. The customer-specified seafoam green coating also improves corrosion resistance and environmental durability.
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2.4 Underground Cable Connection Design
For underground cable applications, the HV side is equipped with 25kV separable insulated connectors rated at 150kV BIL and 200A current capacity for loop-feed distribution systems, while the LV side adopts resin-cast bushings with 6-hole spade terminals for reliable low-voltage cable termination. The underground transformer also includes grounding terminals and rigid copper grounding bus connections to support system grounding and utility protection coordination.
2.5 Protection and Switching System
The protection system includes a 4-position load break switch, bayonet fuses, and ELSP current-limiting backup fuses to provide coordinated transformer protection and improved fault isolation capability. Standard accessories include top oil temperature indication, oil level indication, pressure relief protection, drain valve, and fill plug for routine operation monitoring and maintenance.
03 Testing
Testing Standard
Testing Results
04 Packing and Shipping
05 Site And Summary
These 2000kVA three phase pad mounted underground transformers are specifically designed for Canadian underground utility distribution systems requiring high efficiency, CSA compliance, dead-front operational safety, and reliable loop-feed cable integration.
With low-loss core technology, Dyn1 winding configuration, coordinated fuse protection, sealed tank construction, and utility-grade pad mounted design, the transformers provide a reliable and energy-efficient solution for modern North American underground power distribution networks.
