Reliable, efficient, and safe power with our 500 kVA pad-mounted transformer, delivering stable three-phase electricity for commercial, residential, and industrial use
01 General
1.1 Project Description
In 2024, SCOTECH supplied a 500 kVA three-phase pad-mounted transformer to Canada. It was made according to CSA C227.4:21 and built for reliable power use in commercial buildings, homes, and small factories.
what is a pad mounted transformer?
A pad-mounted transformer is a type of distribution transformer installed at ground level on a concrete base. It is fully enclosed and usually has a dead-front design. This keeps high-voltage parts inside a locked cabinet. It protects the public and utility workers. It also allows easy access for maintenance. The unit has a sealed pad-mounted design and is placed on a concrete pad for safe outdoor use. It changes medium voltage (12.47 / 4.16 kV) to low voltage (0.6 kV) and provides stable and efficient power to users.
It features an ONAN cooling system with mineral oil insulation, offering excellent heat dissipation and a long service life. The transformer runs at 12.47 / 4.16 kV on the primary side and 0.6 kV on the secondary side. It uses a YNyn0 vector group to keep three-phase power balanced. It has aluminum windings, 5% impedance, and 99.5% efficiency. It works with low losses and keeps voltage steady under full load.
In addition to the 500 kVA loop-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 | 12.47GrdY/7.2 × 4.16GrdY/2.4 – 0.6Y/0.347 kV | Radial |
| 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 | Loop |
| 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 | 99.5% |
| Tap Changer | NLTC |
| Tapping Range | ±2*2.5% |
| No Load Loss | ≤1090 W |
| On Load Loss | ≤5800 W |
| Accessories | Standard Configuration |
1.3 Drawings
500kVA three phase pad mounted transformer drawing and nameplate
02 Manufacturing
2.1 Core
The five-limb design gives the core strong support and balance. It helps reduce flux leakage and short-circuit stress. This structure makes the transformer safe, stable, and durable, even when it works in heavy load or outdoor conditions.
2.2 Winding
Specifically for the YNyn0 configuration, workers pay special attention to the neutral point and phase balance during winding to ensure three-phase magnetic circuit balance and short-circuit resistance. The compact winding design reduces losses while maintaining optimal temperature.
2.3 Tank
| The transformer tank is sealed with a bolted cover and made of mild steel. It can take 50 kPa internal pressure without any leakage or permanent deformation more than 0.25% of the surface diagonal. The cabinet is designed to be tamper-resistant and weather-resistant. Captive pentahead bolts are used in line with CSA C227.4 requirements. |  |
2.4 Protection and Monitoring Configuration
All units are equipped with a complete set of protection and monitoring accessories to ensure operational safety and ease of maintenance:
- Pressure relief device with internal fault indicator (IFD)
- Dual-fuse protection system (bayonet + current-limiting fuse)
- Liquid level gauge (magnetic type)
- Maximum indicating thermometer
- Tap changer (±2 × 2.5%, ±2 × 5%)
- Drain valve and oil filling plug
- Anti-corrosion coating for harsh environments
2.5 Final assembly
We adhere to standardized operating procedures, providing clear guidance for every step of transformer assembly and minimizing the uncertainty of manual operation. Combined with a professional team development system, through systematic training and a master-apprentice mechanism, we ensure that every operator is capable of executing high-standard workmanship. This perfect combination of process and people forms the foundation of our most stable product quality.
03 Testing
Testing Standard and Routine Test
| CSA C227.4-21 | Three-phase, pad-mounted distribution transformers with 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 Item | Unit | Acceptance Values | Measured Values | Conclusion | |
| 1 | Resistance Measurements | % | Maximum resistance unbalance rate | 1.27 | Pass |
| 2 | Ratio Tests | % | The deviation of voltage ratio on the principal tapping: ≤0.5% | -0.04-0.10 | Pass |
| 3 | phase-relation tests | / | YNyn0 | YNyn0 | Pass |
| 4 | No-load losses and excitation current | / | I0 :: provide measured value | 0.37% | Pass |
| P0: provide measured value | 0.7317kW | ||||
| 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 | 5.35% | ||||
| Pk: measured value | 4.483kW | ||||
| Pt: measured value | 5.247kW | ||||
| Efficiency not less than 99.05% | 99.29% | ||||
| 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): 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 | 7.8 | / |
| HV&LV to Ground | 8.0 | ||||
| 10 | Oil Test | / | Dielectric Strength; | 51.8 kv | Pass |
| Moisture Content | 11.5 mg/kg | ||||
| Dissipation Factor | 0.00298% | ||||
| Furan Analysis | ≤0.1 | ||||
| Gas Chromatography Analysis | / |
04 Packing and Shipping
05 Site And Summary
Our 500 kVA three-phase pad-mounted transformer gives reliable and efficient power for Canadian distribution networks. It meets CSA C227.4:21 standards. The transformer has a strong five-limb core and precise aluminum windings. The tank is sealed and weatherproof. Skilled workers assemble each unit carefully. The transformer keeps three-phase power balanced and runs with low losses. It uses ONAN cooling and gives stable voltage under full load.
