Robust design, flexible applications—Three-phase pad-mounted transformers meet diverse power needs!
01 General
1.1 Project Description
This 750 kVA pad-mounted transformer, delivered to Guyana in 2024, was engineered to overcome key challenges such as harsh environmental conditions and the demand for a highly reliable, maintenance-efficient power source in radial distribution networks. Our strategic response was a fully enclosed and insulated design from SCOTECH, which integrates robust features including ONAN cooling and a sealed tank without an oil conservator for enhanced durability and minimal upkeep. Critical design elements that directly address these operational challenges are the Dyn11 vector group for superior lightning impulse withstand and neutral point stability, full-range high-voltage fuse protection backed by comprehensive low-voltage safeguards for system reliability, and advanced core/winding technology that ensures low loss, low noise, and safe operation within compact dimensions suitable for diverse settings like residential areas, industrial sites, and infrastructure projects.
1.2 Technical Specification
750 kVA transformer specifications type and data sheet
| Delivered to | Guyana |
| Year | 2024 |
| Type | Pad mounted transformer |
| Standard | IEEE Std C57.12.34-2022 |
| Rated Power | 750KVA |
| Frequency | 60HZ |
| Feed | Radial |
| Front | Live |
| Phase | 3 |
| Cooling Type | ONAN |
| Primary Voltage | 13.8D KV |
| Secondary Voltage | 0.22Y/0.127 KV |
| Winding Material | Copper |
| Angular displacement | Dyn11 |
| Impedance | 4.5% |
| Tap Changer | NLTC |
| Tapping Range | ±2*2.5% |
| No Load Loss | 0.08KW |
| On Load Loss | 1.27KW |
| Accessories | Standard Configuration |
1.3 Drawings
750 kVA pad mounted transformer diagram drawing and size.
02 Manufacturing
2.1 Core
| To overcome the challenges of magnetic imbalance, high energy loss, and mechanical stress in transformer operation, our design strategy employs a symmetrical three-column core structure. This configuration ensures balanced three-phase magnetic flux for minimal leakage and eddy current losses, significantly improving efficiency. The compact, interlocked frame with transverse yokes also provides superior mechanical strength to withstand short-circuit forces and reduce vibration-related damage, ensuring reliable performance. |  |
2.2 Winding
 | To address the critical challenges of enhancing insulation reliability and minimizing energy loss in distribution transformers, our design strategy employs a specialized hybrid winding configuration. This approach combines a foil-wound low-voltage winding to reduce partial discharge and eddy current losses, paired with a segmented high-voltage wire winding that optimizes electric field distribution and reduces magnetic leakage. Together, these features significantly improve the transformer’s insulation performance and operational efficiency. |
2.3 Tank
| The corrugated sheet is used to replace the traditional heat sink, and the corrugated structure can adjust the tank volume according to the thermal expansion and cold contraction, reducing the mechanical stress caused by the change of temperature difference and avoiding the risk of oil leakage. The oil flow design in the tank is compatible with the winding cooling channel to ensure the flow of cooling oil is more uniform and avoid local overheating. The use of welded or high-quality seals to ensure that the tank is completely isolated from the outside world, preventing moisture, air or pollutants from entering, extending the service life of transformer oil and insulation materials. Optimized flange construction and high quality sealing materials reduce the possibility of oil leakage. The tank is made of high quality steel plate and special coating material, which has good corrosion resistance and deformation resistance, and can withstand the external impact during transportation, installation and operation. Specially designed tanks can accommodate special environments such as high humidity, high salt spray or extreme temperature differences. |  |
2.4 Final Assembly
 | Winding Fixation: Securely mount high and low voltage windings on the iron core using insulation and binding materials. Winding Lead Connections: Connect high voltage leads to the sleeve via welding or crimping. Connect low voltage leads to the sleeve or copper bar, secured with fixtures. Neutral Point: Connect to ensure system balance. Tank Insertion: Place the iron core and windings in the tank, aligning with the insulating pad. Accessory Installation: Install external accessories like oil level gauges and pressure relief valves. Vacuum Oil Filling: Use a device to extract air and inject filtered transformer oil. Sealing: Secure the tank cap with gaskets and bolts, welding edges to prevent leaks. |
03 Testing
| No. | Test Item | Unit | Acceptance Values | Measured Values | Conclusion |
| 1 | Resistance Measurements | % | Maximun resistance unbalance rate≤5% | 3.58 | Pass |
| 2 | Ratio Tests | % | The deviation of voltage ratio on the principal tapping: ≤0.5% Connection symbol: Dyn11 | -0.06%-0.05% | Pass |
| 3 | phase-relation tests | / | Dyn11 | Dyn11 | Pass |
| 4 | No-load losses and excitation current | / | I0 :: provide measured value | 0.37% | Pass |
| P0: provide measured value(t:20℃) | 0.979kW | ||||
| 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 | 4.81% | ||||
| Pk: measured value | 9.203kW | ||||
| Pt: measured value | 10.182 kW | ||||
| Efficiency not less than 99.15% | 99.19% | ||||
| 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：20kPA | No leakage and no Damage | Pass |
| Duration：12h | |||||
| 9 | Insulation Resistance Measurement | GΩ | HV-LV to Ground : | 16.5 | / |
| LV-HV to Ground: | 19.2 | ||||
| HV&LV to Ground: | 9.77 | ||||
| 10 | Oil Dielectric Test | kV | ≥45 | 55.23 | Pass |
04 Packing and Shipping
05 Site And Summary
In this rapidly evolving electrical era, our three-phase pad-mounted transformer is your ideal choice. With its innovative design, superior performance, and exceptional safety, it provides reliable solutions for a wide range of power distribution needs. Our product not only enhances efficiency but also improves system stability, ensuring a continuous and reliable power supply. By choosing our three-phase pad-mounted transformer, you are opting for a future-oriented power solution that will help you stand out in a competitive market. Let’s work together towards a sustainable energy future and usher in a new era of power distribution.
