Set It and Forget It. Unwavering Power from Our Three Phase Pad Mounted Transformer.
01 General
1.1 Project Description
500 kVA three phase pad mounted transformer was delivered to Jamaica in 2024. The rated power of the transformer is 500 kVA with ONAN cooling. The high voltage is 23.9GrdY/13.8 kV with ±2*2.5% tapping range (NLTC), the low voltage is 0.22/0.11d kV, they formed a vector group of YNd11.
The pad-mounted transformer is the cornerstone of modern underground electrical distribution, seamlessly bridging the gap between high-voltage utility lines and the low-power needs of homes, businesses, and communities. Engineered for reliability, safety, and aesthetic integration, these robust, steel-enclosed units are a ubiquitous and critical sight in subdivisions, commercial plazas, and industrial parks.
Unlike traditional pole-mounted units, pad-mounted transformers are securely grounded and installed on a concrete slab at ground level. This design prioritizes public safety with a tamper-resistant, locked enclosure that shields live components from unauthorized access and the elements. Their low-profile design minimizes visual and spatial impact, allowing them to blend discreetly into the landscape while delivering essential three-phase or single-phase power.
Built to withstand harsh environmental conditions, our pad-mounted transformers are synonymous with durability and low-maintenance operation. They represent a key investment in a resilient and efficient power infrastructure, ensuring the safe, stable, and dependable delivery of electricity right where it is needed most.
1.2 Technical Specification
500 kVA pad mounted transformer specifications type and data sheet
| Delivered to | USA |
| Year | 2024 |
| Type | Pad mounted transformer |
| Standard | IEEE Std C57.12.34-2022 |
| Rated Power | 500 kVA |
| Frequency | 60HZ |
| Phase | 3 |
| Feed | Loop |
| Front | Dead |
| Cooling Type | ONAN |
| Primary Voltage | 23.9GrdY/13.8 kV |
| Secondary Voltage | 0.22/0.11d kV |
| Winding Material | Copper |
| Vector Group | YNd11 |
| Impedance | 5% |
| Efficiency | 99.26% |
| Tap Changer | NLTC |
| Tapping Range | ±2*2.5% |
| No Load Loss | 0.725 kW |
| On Load Loss | 7.4 kW |
1.3 Drawings
500 kVA pad mounted transformer diagram drawing and size.
02 Manufacturing
2.1 Core
| The transformer employs a compact three-phase five-limb core. This advanced design reduces magnetic losses and noise while improving operational stability, delivering superior performance for modern power distribution needs. |  |
2.2 Winding
 | The pad-mounted transformer features advanced composite windings with low-voltage foil and high-voltage wire constructions, both made of high-conductivity copper. This design ensures excellent heat dissipation, superior short-circuit resistance, and optimal space utilization. The all-copper winding system delivers enhanced efficiency, reduced losses, and reliable performance throughout the transformer’s operational lifecycle. |
2.3 Tank
| The transformer’s tank is constructed from durable mild steel, providing robust mechanical protection and effective heat dissipation for internal components. Its welded structure ensures complete oil-tight integrity while withstanding environmental stresses. The tank design incorporates strategic cooling fins to optimize surface area for thermal management, maintaining stable operating temperatures throughout the service life. |  |
2.4 Final Assembly
 | The final assembly of the pad-mounted transformer integrates core, windings, and components into a sealed mild steel tank, which is then filled with dielectric fluid. The assembly is completed by installing bushings, protective devices, and control accessories onto the sealed tank. |
03 Testing
The test following IEEE standards such as IEEE C57.12.00-2021, IEEE Std C57.12.34-2022, and IEEE C57.12.90-2021. Routine tests included winding resistance measurement, voltage ratio test, phase-relation test, no-load losses and no-load current measurement, load losses/impedance voltage/efficiency test, applied voltage test, induced voltage withstand test, leak test (for liquid-immersed type), insulation resistance measurement, and oil dielectric test.
| No. | Test Item | Unit | Acceptance Values | Measured Values | Conclusion |
| 1 | Resistance Measurements | % | Maximun resistance unbalance rate | 0.44 | Pass |
| 2 | Ratio Tests | % | The deviation of voltage ratio on the principal tapping: ≤0.5% Connection symbol: YNd11 | -0.04% ~ 0.03% | Pass |
| 3 | phase-relation tests | / | YNd11 | YNd11 | Pass |
| 4 | No-load losses and excitation current | / | I0 :: provide measured value | 0.38% | Pass |
| P0: provide measured value(t:20℃) | 0.6546kW | ||||
| the tolerance for no load loss is +10% | / | ||||
| 5 | Load losses impedance voltage and efficiency | / | t:85℃ the tolerance for impedance is ±7.5% the tolerance for total load loss is +6% | / | Pass |
| Z%: measured value | 5.29% | ||||
| Pk: measured value | 7.089kW | ||||
| Pt: measured value | 7.744 kW | ||||
| 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 |
| Induced voltage(KV):0.44 | |||||
| Duration(s):40 | |||||
| Frequency (HZ): 150 | |||||
| 8 | Leakage Test | kPa | Applied pressure: 20kPA | No leakage and no Damage | Pass |
| Duration: 12h | |||||
| 9 | Insulation Resistance Measurement | GΩ | HV-LV to Ground : | OL | / |
| LV-HV to Ground: | OL | ||||
| HV&LV to Ground: | OL | ||||
| 10 | Oil Dielectric Test | kV | ≥45 | 58.3 | Pass |
04 Packing and Shipping
4.1 Packing
| The pad mounted transformer is packaged in a sturdy wooden crate made of plywood, equipped with wooden pallets for easy handling. The crate features shipping labels with handling instructions (e.g., keep upright, protect from impact and rain, do not stack) and specification tags, providing robust protection for long-distance transportation. |  |
4.2 Shipping
 | The transformer packed in durable plywood crates with wooden pallets for stability, is transported by sea under CIF terms to Kingston Port. It is covered by marine insurance against transit risks, and the shipment follows international shipping protocols, with all necessary documents for customs clearance, ensuring it arrives at the destination port safely and in good condition. |
05 Site And Summary
In summary, this pad-mounted transformer combines robust engineering, reliable performance, and durable construction to meet the demands of modern electrical distribution. Designed for safety, efficiency, and long-term operation, it provides a trusted solution for utility and industrial applications. Partner with us for power equipment that delivers excellence-now and for the years to come.
