Reliable and efficient, our Overhead Transformer delivers 347 V lighting power for Canada's commercial grids.
01 General
1.1 Project Description
In 2025, a 75 kVA Overhead Transformer was supplied to Canada for use in medium-voltage distribution networks. The project involved lighting and small commercial loads spread across an urban utility corridor, where the transformer connects directly to a 24.94GrdY/14.4 kV overhead line. It steps the voltage down to 0.347 kV, the standard phase-to-neutral level within Canada’s 600 V Y distribution systems.
Built to CSA C2.2-06 standards, the unit is engineered for reliability in outdoor installations-rain, snow, or summer heat, it keeps running steadily. It features ONAN cooling, aluminum windings, and additive polarity for dependable performance. With 3% impedance, a no-load tap changer (±2×2.5%), and low total losses (141 W no-load / 1,160 W load), it delivers efficient power conversion while minimizing heat and maintenance needs.
The Overhead Transformer is fitted with two arrester supports and an Internal Fault Detector (IFD) that gives an immediate visual alert in the event of internal faults-helping crews act faster and enhancing overall safety. Its compact, pole-mounted design fits easily into existing overhead networks and supports flexible deployment for both upgrades and new installations.
Thanks to its 0.347 kV output, the single phase pole transformer is well-suited for commercial lighting, institutional buildings, and public-area power systems-from schools and offices to street and industrial lighting circuits. Rugged yet efficient, this overhead transformer provides a stable, cost-effective solution for modernizing Canada’s power infrastructure and ensuring reliable energy delivery where it’s needed most.
1.2 Technical Specification
75 kVA pole mounted overhead transformer specifications type and data sheet
| Delivered to | Canada |
| Year | 2025 |
| Type | Pole mounted transformer |
| Standard | CSA C2.2-06 |
| Rated Power | 75 kVA |
| Frequency | 60HZ |
| Phase | 1 |
| Number of Winding | 2 |
| Polarity | Additive |
| Cooling Type | ONAN |
| Primary Voltage | 24.94GrdY/14.4 kV |
| Secondary Voltage | 0.347 kV |
| Winding Material | Aluminum |
| Angular displacement | Ii6 |
| Impedance | 3% |
| Tap Changer | NLTC |
| Tapping Range | ±2*2.5% |
| No Load Loss | 141 kW |
| On Load Loss | 1160 kW |
| Accessories | Arrester Support 2 & IFD 1 |
1.3 Drawings
75 kVA pole mounted overhead transformer diagram drawing and size.
02 Manufacturing
2.1 Core
| Adopting a wound core structure effectively reduces magnetic flux leakage and joint losses, enhancing overall magnetic circuit efficiency. The measured no-load loss is 0.124 kW at rated voltage and 0.152 kW at 105% voltage, with an increase of approximately 22.6%, slightly exceeding the +15% tolerance. Excitation current values of 0.19% and 0.60% still demonstrate good magnetic performance and manufacturing consistency, aligning with the design expectations of wound core transformers. |  |
2.2 Winding
 | The pole mounted overhead transformer adopts a two-winding, single-phase structure with an additive polarity (vector group Ii6). The low-voltage winding uses aluminum foil, offering excellent short-circuit strength and heat dissipation, while ensuring lightweight construction. The high-voltage winding is made of copper round wire, ensuring superior conductivity, mechanical strength, and thermal stability for long-term reliability. |
2.3 Tank
| Our transformer tanks strictly follow customer specs. All surfaces undergo mechanical pretreatment to remove welding burrs, rust, and contaminants, with residues cleaned by vacuum. A thorough coating is applied to all parts, while stainless steel and galvanized bolts, nuts, and threaded rods remain uncoated to preserve their inherent corrosion resistance, ensure mechanical reliability, and facilitate future maintenance as specified. |  |
2.4 Final Assembly
- Preparation
Clean the assembly area thoroughly. Prepare and inspect all qualified materials, including the wound core, pre-wound HV and LV coils, tank, and required accessories.
- Core & Coil Assembly
Assemble the wound core with HV and LV coils, install insulation parts, connect leads to the tap changer and bushings, and secure everything with proper binding and clamping.
- Tanking
Hoist the dried active part into the tank and fix it securely using base bolts to prevent movement during operation.
- Cover Sealing & Accessories
Place sealing gaskets, install the cover with integrated accessories, and tighten bolts evenly. Internally connect leads to bushings. Install components such as nameplate, pressure relief device, IFD, and arrester support as required.
- Vacuum Oil Filling
A critical step—apply high vacuum to thoroughly remove moisture and gases. Under vacuum, fill with qualified insulating oil to the specified level and allow sufficient soaking time, especially important for wound core designs.
- Sealing & Testing
Conduct a 20 kPa airtightness test for 12 hours—no leakage allowed. Adjust oil level and perform a full set of routine tests, including induced voltage withstand, no-load loss, and load loss tests.
- Finishing & Packing
Clean the surface, touch up paint, install terminal protectors, seal the drain valve, and affix the nameplate. Final packaging and storage follow.
03 Testing
Routine Test
- Resistance Measurements
- Ratio Tests
- Polarity Test
- No Load Losses and No Load Current
- Load Losses and Impedance Voltage
- Applied Voltage Test
- Induced Voltage Withstand Test
- Insulation Resistance Measurement
- Oil Dielectric Test
- Leak Testing with Pressure for Liquid Immersed Transformers
Testing Standard
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
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 | -0.03 | Pass |
| 3 | Polarity tests | / | Additive | Additive | Pass |
| 4 | No-load losses and excitation current | % | I0 :: provide measured value（100%） | 0.19 | Pass |
| kW | P0: provide measured value（100%） | 0.124 | |||
| % | I0 :: provide measured value（105%） | 0.60 | |||
| kW | P0: provide measured value（105%） | 0.152 | |||
| / | the tolerance for no load loss is +15% | / | |||
| 5 | Load losses , impedance voltage,total losses and efficiency | / | t:85℃ the tolerance for impedance is ±7.5% the tolerance for total load loss is +8% | / | Pass |
| % | Z%: measured value | 3.10 | |||
| kW | Pk: measured value | 1.020 | |||
| kW | Pt: measured value | 1.144 | |||
| % | Efficiency not less than 98.94% | 99.06 | |||
| 6 | Applied Voltage Test | / | LV: 10kV 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):48 | |||||
| Frequency (HZ): 150 | |||||
| 8 | Insulation Resistance Measurement | GΩ | LV-HV to Ground | 7.49 | Pass |
| 9 | Leakage Test | / | Applied pressure：20kPA | No leakage and no Damage | Pass |
| Duration：12h | |||||
| 10 | Oil Test | kV | Dielectric Strength | 56.1 | Pass |
| mg/kg | Moisture Content | 9.8 | |||
| % | Dissipation Factor | 0.00275 | |||
| mg/kg | Furan Analysis | 0.03 | |||
| / | Gas Chromatography Analysis | / |
04 Packing and Shipping
05 Site and Summary
Transformer capacity is measured in kVA (kilovolt-amperes), showing how much load a transformer can handle safely. Choosing the right pole-mounted transformer depends on expected load, number of users, and room for future growth.
Common Ratings and Applications:
10 kVA: Enough for one or two small houses, maybe a rural farmstead far from the grid.
25–50 kVA: The most common range for small residential clusters-quiet neighborhoods or small offices.
75 kVA and above: Steps into light commercial use-small shops, schools, or workshops.
100–167 kVA: Handles small apartment complexes or groups of businesses sharing a line. 250–333 kVA: A heavier class, used in compact industrial zones, shopping centers, or commercial hubs with steady, concentrated demand.
