Step Up Reliability, Step Down Outages – Substation Transformers Keep the Grid Alive!
01 General
1.1 Project Description
1000/1150 kVA substation transformer was delivered to America in 2025. The rated power of the transformer is 1000/1150 kVA with KNAN/KNAF cooling. The primary voltage is 13.8 kV with ±2*2.5% tapping range (NLTC), the secondary voltage is 0.48GrdY/0.277 kV, they formed a vector group of Dyn1.
The 2000/2300 kVA distribution transformer substation is designed to deliver reliable and efficient power distribution for Junction House – 1. The transformer is filled with FR3® dielectric fluid, a sustainable and high-performance insulating oil that enhances thermal stability, extends equipment lifespan, and provides superior environmental safety compared to conventional mineral oils.
A key safety component of this system is the 5-amp neutral grounding resistor (NGR), which limits fault current and protects the transformer from damage during ground faults. The NGR is monitored via a 5:5 ratio current transformer (CT) with a C10 accuracy rating, ensuring precise fault detection and system protection.
Engineered for durability and compliance with industry standards, this transformer ensures stable power delivery while prioritizing safety, sustainability, and operational efficiency for Junction House – 1.
1.2 Technical Specification
1000/1150 kVA distribution transformer substation specifications type and data sheet
| Delivered to | America |
| Year | 2025 |
| Type | Substation transformer |
| Standard | ANSI/IEEE C57.12.00 |
| Rated Power | 1000/1150 kVA |
| Frequency | 60HZ±6% |
| Phase | 3 |
| Cooling Type | KNAN/KNAF |
| Primary Voltage | 13.8 kV |
| Secondary Voltage | 0.48GrdY/0.277 kV |
| Winding Material | Copper |
| Angular displacement | Dyn1 |
| Impedance | 6% |
| Tap Changer | NLTC |
| Tapping Range | ±2*2.5% |
| No Load Loss | ≤1.335kW |
| On Load Loss | ≤8.2kW |
1.3 Drawings
1000/1150 kVA distribution transformer substation diagram drawing and size.
02 Manufacturing
2.1 Core
The core of a three-phase, three-limb distribution transformer substation is typically constructed using stacked laminated silicon steel sheets to minimize eddy current losses and ensure high magnetic efficiency. This design features three vertical limbs interconnected by upper and lower yokes, providing a balanced magnetic path for the three-phase flux. The stacked-lamination technique enhances mechanical stability, reduces no-load losses, and improves overall transformer performance. Its robust and compact structure makes it ideal for high-power transmission and distribution applications.
2.2 Winding
 | LV Winding: Made of copper foil, tightly layered with interlayer insulation, offering excellent short-circuit strength and thermal performance. HV Winding: Constructed with insulated copper wire in layer-type design, ensuring reliable turn-to-turn insulation for high-voltage endurance and mechanical stability. |
2.3 Tank
| The tank serves as a protective enclosure, fabricated with fully welded corrugated steel or reinforced panels to ensure structural integrity while maximizing heat dissipation. Its surface undergoes sandblasting and multi-layer anti-corrosion coating for long-term outdoor durability. Filled with high-grade insulating oil, the tank provides both electrical insulation and efficient cooling through oil circulation. The tank assembly includes bushings, oil temperature/level indicators, pressure relief devices, and a Buchholz relay. Side walls integrate removable radiators, with drain valves and sampling ports at the bottom, forming a comprehensive system for protection, cooling, and monitoring. |  |
2.4 Final Assembly
 | The final assembly integrates the core, HV/LV windings, and insulation systems into the corrugated tank after vacuum drying and oil filling. Key components like bushings, cooling devices, protective relays, and monitoring systems are installed, followed by hermetic tests and full routine tests to verify mechanical integrity, electrical performance, and operational reliability per standards. |
03 Testing
| No. | Test Item | Unit | Acceptance Values | Measured Values | Conclusion |
| 1 | Resistance Measurements | % | Maximum resistance unbalance rate
| 3.64 | Pass |
| 2 | Ratio Tests | % | The deviation of voltage ratio on the principal tapping: ≤0.5% | -0.03~0.07 | Pass |
| 3 | Phase-relation tests | / | Dyn1 | Dyn1 | Pass |
| 4 | No-load losses and excitation current | % | I0 :: provide measured value | 0.22 | Pass |
| kW | P0: provide measured value | 1.072 | |||
| / | the tolerance for no load loss is +0% | / | |||
| 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 +0% | / | Pass |
| % | Z%: measured value | 5.97 | |||
| kW | Pk: measured value | 7.924 | |||
| kW | Pt: measured value | 8.996 | |||
| % | Efficiency not less than 99.27% | 99.32 | |||
| 6 | Applied Voltage Test | / | HV:34kV 60s LV: 10kV 60s | No collapse of the test voltage occurs | Pass |
| 7 | Induced Voltage Withstand Test | / | Applied voltage (KV):0.96 | No collapse of the test voltage occurs | Pass |
| Duration(s):40 | |||||
| Frequency (HZ): 180 | |||||
| 8 | Insulation Resistance Measurement | GΩ | HV-LV to Ground: | 6.52 | / |
| LV-HV to Ground: | 8.20 | ||||
| HV&LV to Ground: | 6.80 | ||||
| 9 | Leakage Test | / | Applied pressure：50kPA | No leakage and no Damage | Pass |
| Duration：12h | |||||
| 10 | Oil Test | kV | Dielectric Strength | 49.7 | Pass |
| mg/kg | Moisture Content | 186.3 | |||
| % | Dissipation Factor | 2.118 | |||
| mg/kg | Furan Analysis | / | |||
| / | Gas Chromatography Analysis | / |
04 Packing and Shipping
4.1 Packing
The distribution transformer substation is packed with a steel-wood hybrid structure, wrapped with anti-rust film and cushioned with shock-absorbing materials. Steel straps reinforce the exterior, with lifting marks and moisture-proof labels to prevent mechanical damage and environmental corrosion during transportation.
4.2 Shipping
The distribution transformer substation is first transported by heavy-duty truck to the port, with specialized securing devices ensuring stability. Upon arrival container shipping port, it is loaded into a container or flat rack, reinforced, and treated for moisture protection before being shipped via container vessel. During transit, the container is secured on deck or in the hold, with real-time monitoring of temperature, humidity, and vibrations to guarantee safe delivery at the destination port.
05 Site And Summary
As a cornerstone of power systems, our substation transformers stand out for superior reliability, high efficiency, and extended lifespan, ensuring stable energy transmission worldwide. With cutting-edge technology and rigorous quality control, we deliver tailored solutions to meet diverse demands. Choosing our products means embracing safety, performance, and a sustainable energy future.
