From Subdivisions to Smart Cities – Pad-Mounted Transformers Keep Energy Flowing.
01 General
1.1 Project Description
500 kVA pad mounted transformer was delivered to Jamaica in 2025. The rated power of the transformer is 500 kVA with ONAN cooling. The primary voltage is 24/13.8*13.8D*12/6.9 kV with ±2*2.5% tapping range (NLTC), the secondary voltage is 0.416/0.24*0.24D/0.12 kV, they formed vector groups of YNyn0 and YNd11.
Our pad-mounted transformer is a compact, fully enclosed power distribution solution designed for reliability, safety, and efficiency in urban and industrial settings. Engineered for seamless integration into modern grids, it features an off-circuit changer and dual voltage switch for flexible operation, allowing easy voltage adjustment without interrupting service.
For enhanced protection, the unit includes elbow arresters and load-break elbow connectors, ensuring safe disconnection and surge suppression. The feed-thru insert enables efficient cable management, while advanced monitoring is provided via an oil thermometer, liquid level indicator, and vacuum pressure gauge for real-time diagnostics.
Safety is prioritized with a Bay-O-Net fuse and current-limiting fuses to prevent overloads, along with a load break switch for secure isolation during maintenance. Built to withstand harsh environments, this transformer delivers dependable performance with minimal maintenance-ideal for utilities, commercial complexes, and renewable energy applications.
1.2 Technical Specification
500 kVA substation transformer specifications type and data sheet
| Delivered to | America |
| Year | 2025 |
| Type | Substation transformer |
| Standard | IEEE Std C57.12.34-2022 |
| Rated Power | 500 kVA |
| Frequency | 50HZ |
| Phase | 3 |
| Cooling Type | ONAN |
| Primary Voltage | 24/13.8*13.8D*12/6.9 kV |
| Secondary Voltage | 0.416/0.24*0.24D/0.12 kV |
| Winding Material | Copper |
| Angular displacement | YNyn0, YNd11 |
| Impedance | 5% |
| Tap Changer | NLTC |
| Tapping Range | ±2*2.5% |
| No Load Loss | ≤0.767kW |
| On Load Loss | ≤7.2kW |
1.3 Drawings
500 kVA substation transformer diagram drawing and size.
02 Manufacturing
2.1 Core
| The transformer features a high-efficiency stacked iron core constructed from premium grain-oriented silicon steel laminations. Each lamination is precisely laser-cut and layered with interlocking step-lap joints to minimize magnetic flux leakage and reduce no-load losses. The core is coated with an insulating oxide layer to prevent eddy currents, while its compact stacked design enhances mechanical stability and lowers audible noise-critical for urban installations. Rigorously annealed for optimal magnetic permeability, this core ensures smooth energy transfer across dual voltage settings, maintaining efficiency even under fluctuating loads. |  |
2.2 Winding
 | The LV foil winding utilizes copper strip, ensuring uniform current distribution, superior short-circuit resistance, and enhanced heat dissipation. Meanwhile, the HV layer winding adopts insulated copper conductors wound in concentric discs, with interleaved kraft paper for graded dielectric strength. Transposition techniques are applied to minimize eddy losses, while axial and radial cooling ducts optimize thermal management. |
2.3 Tank
| The transformer tank is a robust, corrosion-resistant steel enclosure featuring 3D corrugated walls for oil expansion and integrated cooling fins for passive heat dissipation. With a fully welded, radiographically tested construction, it includes pre-drilled cable ports with grounding bosses, and built-in lifting/forklift points. The interior incorporates baffle plates for optimal oil flow, while UV-resistant epoxy paint ensures long-term durability in outdoor environments. |  |
2.4 Final Assembly
 | The final assembly of this pad-mounted transformer integrates core-coil assembly, tank, and accessories into a unified system. The dried core-winding unit is carefully lowered into the corrosion-resistant steel tank, followed by installation of bushings, cooling fins, and control components. Critical steps include: • Oil filling under vacuum for complete insulation impregnation • Mechanical alignment of load break switches & cable connectors • Functional testing of all monitoring devices (gauges, alarms) |
03 Testing
| No. | Test Item | Unit | Acceptance Values | Measured Values | Conclusion |
| 1 | Resistance Measurements | % | Maximun resistance unbalance rate | 0.76 | Pass |
| 2 | Ratio Tests | % | The deviation of voltage ratio on the principal tapping: ≤±0.5% Connection symbol: YNyn0/YNd11 | 0.14% ~ 0.15% | Pass |
| 3 | phase-relation tests | / | YNyn0/YNd11 | YNyn0/YNd11 | Pass |
| 4 | No-load losses and excitation current | % kW | I0 :: provide measured value P0: provide measured value the tolerance for no load loss is +0% | 0.59% 0.7535 | Pass |
| 5 | Load losses impedance voltage and efficiency | % kW kW | t:85℃ the tolerance for impedance is ±7.5% the tolerance for total load loss is +0% | / | Pass |
| Z%: measured value | 5.02% | ||||
| Pk: measured value | 6.649kW | ||||
| Pt: measured value | 7.4025kW | ||||
| Efficiency not less than 99.05% | 99.10% | ||||
| 6 | Applied Voltage Test | kV | HV: 40kV 60s LV: 10kV 60s | No collapse of the test voltage occurs | Pass |
| 7 | Induced Voltage Withstand Test | kV | Applied voltage (KV):2Ur | No collapse of the test voltage occurs | Pass |
| Duration(s):40 | |||||
| Frequency (HZ): 150 | |||||
| 8 | Leakage Test | kPa | Applied pressure：20kPA Duration：12h | No leakage and no Damage | Pass |
| 9 | Insulation Resistance Measurement | GΩ | HV-LV to Ground : | 11.0 | / |
| LV-HV to Ground: | 9.51 | ||||
| HV&LV to Ground: | 20.1 | ||||
| 10 | Oil Dielectric Test | kV | ≥45 | 58.6 | Pass |
04 Packing and Shipping
4.1 Packing
| This pad mounted transformer is packaged by first laying a layer of tin foil bag on the transformer tray and covering the transformer with the tin foil bag. When sealing the tin foil bag, an opening should be left, through which a vacuum cleaner is used to extract the gas, and then the opening is sealed with a sealing machine. Meanwhile, desiccant is placed inside the package to prevent rust. After vacuuming, corner protectors made of foam, plastic, or cardboard (special corner protectors pressed from cardboard) are added around the transformer, which is then wrapped with protective film. Finally, it is packed into a wooden box, on which forklift markings and center of gravity markings should be sprayed. |  |
4.2 Shipping
 | This pad-mounted transformer will be shipped under FOB (Free On Board) terms, with the supplier responsible for delivering the goods to Yiwu Port and completing the loading onto the vessel. Ownership and risk transfer to the buyer once the goods pass the ship’s rail at Yiwu Port. Subsequent ocean freight and final delivery to Jamaica will be arranged by the buyer. During transit, the equipment must be securely fastened to prevent vibration and moisture, with complete packing lists and export documents provided for customs clearance. |
05 Site And Summary
With high efficiency, compact design, and robust durability, this Pad-Mounted Transformer is the ideal choice for industrial, commercial, and public utility power systems. Manufactured in strict compliance with international standards, every unit guarantees superior performance and safety. Whether you need reliable power distribution or customized solutions for challenging environments, our team is ready to provide expert support. Contact us today for detailed specifications or tailored services-we’re committed to delivering stable and efficient power solutions for your needs!
