69kV 30 MVA 35 MVA Power Transformer
- Primary Voltage Ratings: 69 kV
- Secondary Voltage Ratings: 13.8 kV
- H.V. TAP RANGE: ±8*1.25%
- CONNECTION TYPE: YNhd
- TYPE: 3 phase
- Application: 69kV Substation
- Power Rating: 30MVA & 35MVA
- Cooling Method: ONAN & ONAF
The 69kV 30 MVA / 35 MVA power transformer, designed and manufactured by Daelim Transformer in 2016, serves a 69kV substation in Ecuador. Featuring a three-phase, dual-winding core type structure, it operates at 30 MVA with natural air cooling (ONAN) and up to 35 MVA with fan assistance (ONAF). The transformer includes on-load voltage regulation with a ±8 × 1.25% range. Key components include high and low voltage bushings, an oil conservator, and a fan. Daelim Transformer is dedicated to "Empowering Progress with Precision and Reliability," ensuring superior performance and efficiency.
Quote Now

The 69kV 30 MVA / 35 MVA power transformer was designed and manufactured by Daelim Transformer in 2016. It is utilized in a 69kV substation in Ecuador. This transformer features a three-phase, dual-winding core type structure with a primary voltage of 69 kV and a secondary voltage of 13.8 kV. The cooling system is a one-stage design: it operates at a full load capacity of 30 MVA under natural air cooling (ONAN), and can reach up to 35 MVA when the fan is activated (ONAF).
- Core Material: Cold-rolled silicon steel
- Core Structure: Stacked core
- High Voltage Winding: 69 kV
- Low Voltage Winding: 13.8 kV
- Rated Frequency: 60 Hz
- Rated Capacity: 35,000 kVA
- Phase: 3
- Voltage Regulation Method: On-load voltage regulation
- Voltage Regulation Range: ±8 × 1.25%
- Neutral Point Grounding Method: Ungrounded
- Cooling Method: ONAN (30 MVA) / ONAF (35 MVA)
- Link Group Label: YNhd
- Impedance Voltage (35 MVA): 10.34%
- Load Loss: 32 kW
- Load Loss (ONAN): 110 kW
Insulation Levels:
- High Voltage Lightning Impulse Voltage (Full Wave, Peak Value): 360 kV
- High Voltage Lightning Impulse Voltage (Chopped Wave, Peak Value): 325 kV
- Rated Short-Time Power Frequency Withstand Voltage (Effective Value): 140 kV
- Low Voltage Lightning Impulse Voltage (Full Wave, Peak Value): 75 kV
- Low Voltage Lightning Impulse Voltage (Chopped Wave, Peak Value): 85 kV
- Rated Short-Time Power Frequency Withstand Voltage (Effective Value): 35 kV
Temperature Rise:
- Top Oil: 60 K
- Winding (Average): 65 K
- Winding (Hot Spot): 78 K
- Core, Oil Tank, and Structural Surface: 75 K
Noise Level: 58 dB
Pressure Relief Device:
- Release Pressure: 0.055 MPa
- Resume Pressure: 0.0295 MPa
Components (35 MVA Version):
- 72.5 kV High Voltage Bushings
- 25 kV Pure Porcelain Low Voltage Bushings
- Oil Conservator (Including Oil Level Gauge, Capsule, etc.)
- Tap Changer
- Temperature Indicator
- Pressure Relief Device
- Oil Drain Valve
- Stainless Steel Nameplates
- Fan
- Stainless Steel Wind Control Box
At Daelim Transformer, we are committed to excellence and innovation in every transformer we design and manufacture. Our transformers are engineered to deliver reliability and efficiency, ensuring optimal performance for your power needs. "Empowering Progress with Precision and Reliability"—this is our promise to you.
Related Products
Related Article
Single Phase Pole Mounted Transformer For Guyana
In August 2023, Daelim Transformer completed production and Factory Acceptance Testing (FAT) for a batch of single-phase pole-mounted transformers. These transformers are destined for a prominent distributor in Guyana. The customized order comprises 44 units transformers, with 32 units of 50 kVA, 6 units of 100 kVA, and 6 units of 167 kVA. All adhere to traditional design principles, featuring dual high-pressure bushings. The standard manufacturing and testing procedures follow IEEE Std C57, with the specified type as Conventional.
4000 kVA Three Phase Power Transformer For Canada
A Canadian customer has shared photos with us, showcasing the installation and operation of two 4000kVA transformers designed and produced by Daelim Transformer. The transformers have received highly positive feedback from the customers, who found them to be efficient and expressed satisfaction with the collaborative experience working with the Daelim Transformer team. We look forward to further expanding our cooperation with Daelim Transformer in the future.
230 kV Three Phase Power Transformer For USA Market
In 2023, Daelim Transformer designed and manufactured a cutting-edge 230 kV three-phase power transformer for a client in Nevada, USA. The client recently shared installation and operational photos, showcasing the successful deployment of this remarkable transformer. Let's delve into the specifics of this transformer project!
Single Phase Pad Mounted Transformer For USA Utility
Introducing a utility transformer project tailored for the USA, located in Virginia. This utility initiative requires 215 units of single-phase pad-mounted transformers, all UL listed, including 175 units of 25 kVA and 40 units of 50 kVA. The end user's project timeline is 90 days. Adherence to IEEE standards is imperative for single-phase transformers. Additionally, the design of transformer components and markings must be customized to meet project specifications.
Canadian 69 kV Substation Transformer Project
Today, we are excited to present a case study on a 69 kV substation transformer project by Daelim Transformer. Our Canadian client required a step-down transformer for their substation to connect with the hydroelectric grid in Quebec.
Pad Mounted Transformer for BESS System 4.0 MVA in Riverside County, California
Today, Daelim Transformer is proud to introduce a pad-mounted transformer for a 4.0 MVA Battery Energy Storage System (BESS) project located in Riverside County, California. The transformer is meticulously crafted to comply with the specifications outlined in the California Electrical Code Article 450.
13.8 kV 10.5 MVA Substation Transformer for Ecuador
A customer from Ecuador contacted Daelim Transformer for a 10.5MVA substation transformer (13.8kV high voltage, 2.4kV low voltage). Daelim Transformer provided a customized solution, conducted virtual factory tours, ensured rigorous quality control via video inspections, and offered post-delivery online training and ongoing support, fostering a successful partnership.
20MVA Power Transformer for the United States
This project involves the development of a 20 MVA three-phase power transformer tailored for the United States market. The primary voltage is 24.94kV, and the secondary voltage is 4.16kV, indicating it functions as a step-down transformer. The design and production fully comply with IEEE C57.12.00 standards and have passed third-party UL team testing. All accessories also adhere to IEEE standards. FR3 vegetable oil serves as the insulating liquid for the transformers.
Pad Mounted Transformer For High Voltage Substation
FWS commissioned Daelim Transformer to design and manufacture a new high voltage substation for the Richardson International Canola Crush facility expansion in Yorkton, SK. The project required two specially designed top-in pad-mounted transformers, one 2 MVA and one 5 MVA. Unable to meet the delivery deadline, local North American suppliers led FWS to choose Daelim Transformer for their capacity and quality. The transformers were successfully produced and delivered within 16 weeks and are now operating safely.






