High-efficiency 500 kVA Radial Feed Transformer for reliable and compact power distribution
01 General
1.1 Project Description
In 2024, a Canadian client received a 500 kVA three-phase pad-mounted transformer from Scotech. The transformer was designed and made according to CSA Standard C227.4:21. The unit is for outdoor installation on a concrete pad. It provides a compact and safe solution for residential and commercial power distribution.
This 500 kVA radial feed transformer uses ONAN cooling and mineral oil for insulation. The aluminum windings give a good balance of efficiency, weight, and cost. It is rated 500 kVA, 60 Hz, with primary voltage of 12.47/4.16 kV and secondary voltage of 0.6 kV, arranged in a YNyn0 vector group.
The unit is designed for radial feed networks, which deliver power in a single path from the substation to the customer. Radial systems are simple, cost-effective, and suitable for areas where reliability can be managed with sectionalizing switches.
To allow flexible voltage regulation, the transformer is equipped with a no-load tap changer (NLTC), offering a ±2×2.5% tapping range. It achieves 99.05% efficiency, with no-load losses ≤1090 W and load losses ≤5800 W. Built for durability, it comes with standard CSA-compliant accessories and represents a reliable solution for Canadian distribution networks.
In addition to the 500 kVA radial-type unit featured above, the customer also ordered the following pad-mounted transformers under the same project:
| Capacity (kVA) | Voltage Configuration | Type |
|---|---|---|
| 300 | 12.47GrdY/7.2 × 4.16GrdY/2.4 – 0.208Y/0.12 kV | Loop |
| 300 | 12.47GrdY/7.2 – 0.208Y/0.12 kV | Radial |
| 500 | 12.47GrdY/7.2 × 4.16GrdY/2.4 – 0.208Y/0.12 kV | Loop |
| 500 | 500 kVA 12.47Grdy/7.2 X 4.16Grdy/2.4-0.6y/0.347 | Loop |
| 750 | 12.47GrdY/7.2 – 0.6Y/0.347 kV | Radial |
This project involves the supply of multiple three-phase pad-mounted distribution transformers delivered for outdoor installation on grounded distribution systems, designed in full compliance with CSA C227.4 standards and tailored to meet diversified load requirements across the site-covering commercial low-voltage utilization, medium-voltage distribution stepping, and mixed feeder configurations under both radial and loop network conditions.
1.2 Technical Specification
500kVA three phase pad mounted transformer specification and data sheet
| Delivered to | Canada |
| Year | 2024 |
| Type | Three phase pad mount transformer |
| Standard | CSA C227.4:21 |
| Rated Power | 500KVA |
| Frequency | 60HZ |
| Feed | Radial |
| Front | Dead |
| Phase | three |
| Cooling Type | ONAN |
| Liquid insulant | Mineral Oil |
| Primary Voltage | 12.47(4.16) kV |
| Secondary Voltage | 0.6 kV |
| Vector Group | YNyn0 |
| Winding Material | Aluminum |
| Impedance | 5 % |
| Efficiency | 99.05% |
| Tap Changer | NLTC |
| Tapping Range | ±2*2.5% |
| No Load Loss | ≤1090 W |
| On Load Loss | ≤5800 W |
| Accessories | Standard Configuration |
1.3 Drawings
500 kVA radial feed transformer drawing and nameplate
02 Manufacturing
2.1 Core
The five-limb core keeps magnetic flux balanced in all three phases. This design reduces stray flux and loss. The core uses 0.30–0.35 mm silicon steel sheets with high magnetic strength and low resistance. The result is better efficiency and lower noise during operation.
2.2 Winding
This transformer features aluminum windings. The coils are wound with foil for the low voltage and wire for the high voltage. This design ensures uniform current distribution, strong short-circuit resistance, and effective cooling. With a 5% impedance and 99.05% efficiency, this transformer delivers stable and efficient performance under various load conditions.
2.3 Tank
| A sealed mild-steel tank with bolted cover is used for the transformer. It can withstand 50 kPa internal pressure with no leaks or distortion greater than 0.25% of the diagonal dimension. The cabinet is built for outdoor use, tamper-resistant and weather-resistant, and is secured with captive pentahead bolts as shown in CSA C227.4. |  |
2.4 Final assembly
We have a professionally trained and rigorously assessed assembly team, who continuously pass on valuable practical experience through a master-apprentice system. At the production site, we implement lean process control, ensuring that every transformer assembly process is under control through comprehensive quality inspections and key data recording. The organic combination of professional team execution and lean control supervision ensures exceptional quality.
03 Testing
Testing Standard and Routine Test
CSA C227.4-21: Three-phase, pad-mounted distribution transformerswith separable insulated high-voltage connectors
CSA-C802.1-13 (R2022)：Minimum Efficiency Values for Liquid-Filled Distribution Transformers
1. Resistance Measurements
2. Ratio Tests
3. Phase Relation Test
4. No Load Losses and No Load Current
5. Load Losses Impedance Voltage and Efficiency
6. Applied Voltage Test
7. Induced Voltage Withstand Test
8. Leak Testing with Pressure for Liquid Immersed Transformers
9. Insulation Resistance Measurement
10. Oil Dielectric Test
Test Results
| No. | Test Item | Unit | Acceptance Values | Measured Values | Conclusion |
| 1 | Resistance Measurements | % | Maximum resistance unbalance rate | 1.17 | Pass |
| 2 | Ratio Tests | % | The deviation of voltage ratio on the principal tapping: ≤0.5% | -0.03-0.10 | Pass |
| 3 | phase-relation tests | / | YNyn0 | YNyn0 | Pass |
| 4 | No-load losses and excitation current | / | I0 :: provide measured value | 0.39% | Pass |
| P0: provide measured value | 0.7455kW | ||||
| 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 | 5.36% | ||||
| Pk: measured value | 4.534kW | ||||
| Pt: measured value | 5.312kW | ||||
| Efficiency not less than 99.05% | 99.28% | ||||
| 6 | Applied Voltage Test | kV | LV: 10kV 60s | No collapse of the test voltage occurs | Pass |
| 7 | Induced Voltage Withstand Test | kV | Applied voltage (KV): 2 Ur | No collapse of the test voltage occurs | Pass |
| Duration(s):30 | |||||
| Frequency (HZ): 240 | |||||
| 8 | Leakage Test | kPa | Applied pressure：20kPA Duration：12h | No leakage and no Damage | Pass
|
| 9 | Insulation Resistance Measurement | GΩ | LV-HV to Ground | 6.3 | / |
| HV&LV to Ground | 9.5 | ||||
| 10 | Oil Test | / | Dielectric Strength; | 56.2 kv | Pass |
| Moisture Content | 11.9 mg/kg | ||||
| Dissipation Factor | 0.00342% | ||||
| Furan Analysis | ≤0.1 | ||||
| Gas Chromatography Analysis | / |
04 Packing and Shipping
05 Site And Summary
This 500 kVA three-phase pad-mounted transformer is built for Canada. It follows CSA C227.4:21 and is made for safe, efficient outdoor power distribution. It has a compact pad-mounted design and works well in both residential and commercial networks. The five-limb core design keeps magnetic balance and reduces noise. The sealed steel tank is strong, weatherproof, and tamperproof. Each transformer is made by skilled workers under strict quality control. It runs with 99.05% efficiency, low loss, and stable voltage. It is a durable and trusted choice for Canadian power systems.
