1000 kVA pad mount transformer-smart power for commercial centers, with dual-fuse protection and reliable 13.8kV to 460Y/266V conversion
01 General
1.1 Project Description
In April 2025, one of our long-term customers in Guyana placed an order for two transformers: a 1000kVA 13.8kV–460Y/266V three-phase pad-mounted transformer and a 400kVA 460–220/127V VPI dry-type transformer.
The 1000 kva pad mount transformer is built to IEEE Std C57.12.34-2022 standards and features a loop feed design with a dead-front front-access configuration. It adopts ONAN (Oil Natural Air Natural) cooling and is insulated with mineral oil. The primary voltage is 13.8kV, and the secondary voltage is 460Y/266V, with a Dyn11 vector group and 5.75% impedance.
The transformer is equipped with three Bayonet fuses and three ELSP current-limiting backup fuses. Bayonet Fuse provides protection for the low fault current segment. ELSP Fuse quickly cuts off the current and limits the arc energy when a high current short circuit occurs. When combined, it covers the full range of fault protection from low to high current. It is a perfect match for the needs of a safe, stable, easy to maintain and cost-effective power distribution system.
1000 kVA three-phase pad mount transformer is suitable for supermarkets & commercial centers. 13.8kV is connected to the municipal distribution network, and 460V is used for commercial air conditioners, lighting, elevators and other loads. Because the various loads of commercial appliances require stable three-phase power supply, the transformer output of 460Y/266V is just enough. Double fuse protection improves the safety level and reduces property losses caused by faults.
1.2 Technical Specification
1000kVA three phase pad mounted transformer specification and data sheet
| Delivered to | Guyana |
| Year | 2025 |
| Type | Three phase pad mount transformer |
| Standard | IEEE Std C57.12.34-2022 |
| Rated Power | 1000KVA |
| Frequency | 60HZ |
| Feed | Loop |
| Front | Dead |
| Phase | three |
| Cooling Type | ONAN |
| Liquid insulant | Mineral Oil |
| Primary Voltage | 13.8 Kv |
| Secondary Voltage | 0.46 Kv |
| Vector Group | Dyn11 |
| Winding Material | Copper |
| Impedance | 5.75% |
| Tap Changer | NLTC |
| Tapping Range | ±2*2.5% |
| Efficiency | 99.15% |
| No Load Loss | 1600 W |
| On Load Loss | 11800 W |
| Accessories | Standard Configuration |
1.3 Drawings
1000kVA three phase pad mounted transformer dimensions and weight details
02 Manufacturing
2.1 Core
The three-phase three-limb core adopts fully mitered joints, utilizing cold-rolled grain-oriented silicon steel sheets to further reduce no-load loss and fully leverage the material’s magnetic properties. By using fully mitered joints, the magnetic flux remains aligned with the rolling direction of the steel, thereby minimizing core losses. However, this jointing process is more complex, and the mechanical integrity of the stacked core may be reduced.
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2.2 Winding
 | The transformer adopts low voltage foil winding and high voltage wire winding structure. The high voltage winding adopts 1.5×4 mm rectangular copper conductor. This combination provides excellent thermal performance, compact structure and reliable electrical characteristics. |
2.3 Tank
The transformer features a sealed tank with a bolted cover, fabricated from high-quality mild steel. Radiators are welded on both sides and the rear of the tank to enhance heat dissipation. The tank design ensures robust mechanical strength and effective cooling for liquid-immersed operation. To ensure reliability, the tank is pressure-tested at 50 kPa for 24 hours with no leakage or deformation. |  |
2.4 Elsp Fuse
 | Our three-phase pad-mounted transformer adopts Eaton’s ELSP current-limiting backup fuse, paired with a Bay-O-Net fuse to form a dual protection system. This fuse features high-efficiency current limiting performance, effectively reducing the impact of fault currents on the equipment, and is suitable for use in transformer mineral oil. |
2.5 Final Assembly
1. Core and Winding Assembly Assemble the active part (core and winding). The leads shown in the picture are prepared for welding. 2. Main Tank Installation 3. Accessory Installation This 1000 kva pad mount transformer uses a combination of Bay-O-Net fuse and ELSP current-limiting backup fuse, which is a typical protection scheme for oil-immersed distribution transformers in North America. 4. Oil Filling and Sealing Fill the transformer with insulating oil and seal the tank. 5. Electrical Connections and Inspection 6. Final Appearance and Labeling Check |  |
03 Testing
Routine Test and Testing Standard
- Winding Resistance Measurement: According to IEEE C57.12.90-2021 Clause 5
- Voltage Ratio Measurement: According to IEEE C57.12.90-2021 Clause 7
- Phase Displacement Test: According to IEEE C57.12.90-2021 Clause 6
- No-load Loss and No-load Current Measurement: According to IEEE C57.12.90-2021 Clause 8
- Load Loss, Impedance Voltage, and Efficiency Measurement： According to IEEE C57.12.90-2021 Clause 9 and CSA-C802.1-13 Clause 6
- Applied Voltage Test： According to IEEE C57.12.90-2021 Clause 10.6
- Induced Voltage Withstand Test： According to IEEE C57.12.90-2021 Clause 10.5.1
- Leakage Test with Pressure for Liquid-Immersed Transformers： The leaking test at 50KPa shall be conducted for 24h without leakage. No permanent deformation.
- Insulation Resistance Measurement
- Dielectric Strength Test of Transformer Oil
Test Results
| No. | Test Item | Unit | Acceptance Values | Measured Values | Conclusion |
| 1 | Resistance Measurements | % | Maximum resistance unbalance rate≤5% | 1.68 | Pass |
| 2 | Ratio Tests | % | The deviation of voltage ratio on the principal tapping: ≤0.5% Connection symbol: Dyn11 | -0.09%~-0.08% | Pass |
| 3 | phase-relation tests | / | Dyn11 | Dyn11 | Pass |
| 4 | No-load losses and excitation current | / | I0 :: provide measured value | 0.77% | Pass |
| P0: provide measured value（t:20℃） | 1.465kW | ||||
| 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 | 5.62% | ||||
| Pk: measured value | 11.085kW | ||||
| Pt: measured value | 12.550 kW | ||||
| Efficiency not less than 99.15% | 99.21% | ||||
| 6 | Applied Voltage Test | kV | HV: 34kV 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): 27.6 | |||||
| Duration(s):48 | |||||
| Frequency (HZ): 150 | |||||
| 8 | Leakage Test | kPa | Applied pressure：50kPA | No leakage and no Damage | Pass |
| Duration：24h | |||||
| 9 | Insulation Resistance Measurement | GΩ | HV-LV to Ground : | 48.4 | / |
| LV-HV to Ground: | 65.5 | ||||
| HV&LV to Ground: | 51.9 | ||||
| 10 | Oil Dielectric Test | kV | ≥45 | 56.5 | Pass |
04 Site And Summary
SCOTECH delivers more than 12,000,000 kVA transformers across the globe every year, powering countless homes and businesses. We have rich experience in designing and producing three phase pad mounted transformers. Whether it is the CSA Standard or the IEEE Standard, we have a lot of cases. Rated power from 100 kVA up to 5000 KVA. We ensure that each unit undergoes rigorous full acceptance testing. Hope to gain your trust.
