Reliable and efficient 50 kVA pole mounted transformer with high-voltage double bushings and lightning protection for safe outdoor power
01 General
1.1 Project Description
Three 50 kva pole mounted transformers were delivered to a Canadian client by Scotech in 2024. Guarantee alignment with CSA C2.2-06 standards. These units are engineered to operate at a nominal input voltage of 25 kV, delivering 0.347 kV on the secondary side, with a maximum capacity of 50 kVA. They use ONAN natural oil cooling and mineral oil insulation, combined with additive polarity and a vector group Ii6, which together help maintain stable voltage and efficient power delivery.
Aluminum windings reduce weight and cost. 2.3% impedance balances short-circuit current and voltage. NLTC with ±2 × 2.5% steps keeps output stable under load. 33 kV polymer lightning arresters and dual high-voltage bushings protect against lightning and overvoltage. PRD releases pressure safely.
Voltage combination is common in North American and Canadian distribution networks. Suitable for rural areas, residential clusters, and small businesses. Works on feeder circuits, ring networks, and branch lines. Strong for pole-mounted outdoor use, even in high lightning areas. Provides stable, efficient, reliable power.
1.2 Technical Specification
50 kva pole mounted transformer specification and data sheet
| Delivered to | Canada |
| Year | 2024 |
| Type | Pole Mounted Transformer |
| Standard | CSA C2.2-06 |
| Rated Power | 50kVA |
| Frequency | 60HZ |
| Polarity | Additive |
| Phase | 1 |
| Cooling Type | ONAN |
| Liquid insulant | Mineral Oil |
| Primary Voltage | 25 kV |
| Secondary Voltage | 0.347 kV |
| Vector Group | Ii6 |
| Winding Material | Aluminum |
| Impedance | 2.3 % |
| Efficiency | 98.84% |
| Tap Changer | NLTC |
| Tapping Range | ±2*2.5% |
| No Load Loss | 135 kV |
| On Load Loss | 705 kV |
| Accessories | Arrester |
1.3 Drawings
50 kva pole mounted transformer dimensions and weight details
02 Manufacturing
2.1 Core
Our transformer core is made of cold-rolled silicon steel. It has low iron loss and high magnetic permeability. The surface has a uniform coating. It prevents oxidation and resists corrosion. Laminations are stacked tightly. Insulated layers keep mechanical strength and reduce eddy current loss. The core is clamped firmly. It reduces vibration and noise during no-load operation or lightning strikes.
2.2 Winding
 | Before winding, the direction and polarity must be clearly defined to ensure correct terminal markings and prevent phase errors. Each coil uses pure aluminum wire with good conductivity and corrosion resistance. The winding follows correct polarity. Low-voltage is inside, high-voltage outside. Insulation is tight, tension controlled. Oil ducts and pressing ensure cooling and strength. |
2.3 Tank
| Our transformer tank is designed with strong flanges and mounting supports to safely hold surge arresters. The top panel can bear the arrester weight and external forces. Mounting holes are flat and secure. The tank material resists heat and pressure from lightning or operation. Sealing with rubber gaskets prevents oil leaks. The surface is anti-corrosion. Maintenance space is reserved for easy arrester replacement without affecting overall sealing. |  |
2.4 Final Assembly
 | Core and Winding Assembly Install the high-voltage and low-voltage windings onto the core, ensuring insulation and concentricity. Body Installation Place the core and winding assembly into the oil tank. Install leads and insulating bushings, ensuring proper sealing. Filling Transformer Oil Inject filtered transformer oil, ensuring it is clean and free of impurities. Install External Accessories Attach safety valves, oil level gauges, and terminal connections. |
03 Testing
Testing Standard and Routine Test
| CSA C2.2-06（R2022） | Single-phase and three-phase liquid-filled distribution transformers |
CSA C802.1-13（R2022） Minimum efficiency values for liquid-filled distribution transformers
1 Resistance Measurements
2 Ratio Tests
3 Polarity Test
4 No Load Losses and No Load Current
5 Load Losses and Impedance Voltage
6 Applied Voltage Test
7 Induced Voltage Withstand Test
8 Insulation Resistance Measurement
9 Leak Testing with Pressure for Liquid Immersed Transformers
10 Oil Test
Test Results
| No. | Test Item | Unit | Acceptance Values | Measured Values | Conclusion |
| 1 | Resistance Measurements | / | / | / | Pass |
| 2 | Ratio Tests | / | The deviation of voltage ratio on the principal tapping: ≤0.5% Connection symbol: Ii6 | 0.05 | Pass |
| 3 | Polarity tests | / | Additive | Additive | Pass |
| 4 | No-load losses and excitation current | % | I0 :: provide measured value（100%） | 0.33 | Pass |
| kW | P0: provide measured value（100%） | 0.1151 | |||
| % | I0 :: provide measured value（105%） | 0.34 | |||
| kW | P0: provide measured value（105%） | 0.1283 | |||
| / | the tolerance for no load loss is +10% | / | |||
| 5 | Load losses , impedance voltage,total losses and efficiency | / | t:85℃ the tolerance for impedance is ±15% the tolerance for total load loss is +6% | / | Pass |
| % | Z%: measured value | 2.33 | |||
| kW | Pk: measured value | 0.640 | |||
| kW | Pt: measured value | 0.7551 | |||
| % | Efficiency not less than 98.84% | 98.97 | |||
| 6 | Applied Voltage Test | / | LV: 10kV 60s HV：40kV 60s | No collapse of the test voltage occurs | Pass |
| 7 | Induced Voltage Withstand Test | / | Applied voltage (KV):2Ur | No collapse of the test voltage occurs | Pass |
| Duration(s):40 | |||||
| Frequency (HZ): 180 | |||||
| 8 | Insulation Resistance Measurement | GΩ | HV-LV·to·Ground | 361 | Pass |
| LV-HV to Ground | 427 | ||||
| HV&LV to Ground | 233 | ||||
| 9 | Leakage Test | / | Applied pressure：20kPA | No leakage and no Damage | Pass |
| Duration：12h | |||||
| 10 | Oil Test
| kV | Dielectric Strength | 54.3 | Pass |
| mg/kg | Moisture Content | 10.9 | |||
| % | Dissipation Factor | 0.096 | |||
| mg/kg | Furan Analysis | ≤0.1 | |||
| / | Gas Chromatography Analysis | / |
04 Packing and Shipping
05 Site and Summary
Scotech 50 kva pole mounted transformer – lightweight aluminum windings. It uses ONAN cooling. NLTC tap changer and 33 kV lightning protection keep power reliable and safe. It delivers efficient outdoor power for rural and residential networks.
