1,000+ Electrical Transformers (7.2–34.5 kV, 25–3000 kVA) — UL Evaluated, Certificate of Compliance Available — In Stock & Ready to Ship from Houston, CA & Florida. Contact Us Today!
BESS transformers are available in different configurations, depending on the capacity of the energy storage system, inverter specifications and grid requirements.
Technical characteristics of our BESS transformers:
Technical specification of Daelim Transformer’s BESS transformers | |
Transformer Parameter | Typical Range |
Rated power | 1000 kVA – 500 MVA |
Low / Medium voltage (solar plant / inverter side) | 400 V – 35000 V |
High voltage (power grid side) | Up to 345 kV |
Frequency | 50 / 60 Hz |
Cooling methods | ONAN – ONAF – OFAF – OFWF |
Tap changer | DETC ±5%, 21 position OLTC -10% to +15% available |
Winding material | Copper or Aluminium |
Corrosion Protection Class | C3 / C4 / C5 |
Insulation fluid | Mineral oil or natural ester |
Installation type | Indoor and Outdoor |
Ambient temperature | −40 °C to +50 °C |
Standards | IEC – ANSI/IEEE – CSA – AS/NZS |
Delivery time | 12-16 weeks (standard transformers) 4 to 8 months (custom and large transformers) |
Operational life | 25 – 30 years |
The transformers are built from high-grade magnetic core materials that minimize losses. Also, this core ensures the integrity of the transformer structure under high loads. The windings are manufactured with a high degree of insulation and with optimized conductor laying geometry. Together, these features ensure stable transformer performance in the demanding environment of battery and renewable interaction with the grid.
The use of biodegradable oils and high flash point insulation ensures a lower environmental impact of BESS transformers. Also, the proximity of battery systems requires increased fire protection measures for BESS transformers. The oils and insulation materials used in Daelim Transformer BESS transformers are FM-certified, confirming compliance with fire safety and overall performance standards. The entire design of the Daelim Transformer transformer is focused on reducing the environmental footprint throughout the entire lifecycle.
Every Daelim Transformer’s BESS transformer is supplied with a complete electrostatic shield between the HV and LV windings. This is a standard, not an optional design. This improves the insulation between the windings, reduces the risk of partial discharges and increases the dielectric strength. It protects the equipment and extends the service life of the transformer.
The designed service life of BESS transformers is over 20 years. The transformer with a sealed tank and a conservator equipped with an air-isolation system, providing a high level of protection against moisture ingress and environmental contamination.. Units with capacities up to 20 MVA are usually manufactured in a hermetically sealed design, incorporating nitrogen-cushion protection as well as additional devices such as sudden-pressure relays and vacuum gauges. BESS transformers exceeding 20 MW and rated voltages above 50 kV typically employ a conservator-type design. They are equipped with Buchholz relays, winding thermometers and additional smart monitoring devices -such as SEL-2414 and Qualitrol W9.
In its two production units, Daelim Transformer produces over 5000 transformers per year. Many years of experience in the production of standard and customized units, enables extremely fast delivery of your transformer. We maintain hundreds of BESS transformers in stock, with ratings ranging from 1,000 kVA to 5,000 kVA. No lead time required—contact us today and your transformer can be shipped within one week. Our BESS transformers work on all continents, and are adapted to all the most used standards, which further speeds up the design and transformer manufacturing.
BESS transformers play a key role in the renewable energy sector by enabling seamless integration with the distribution and transmission grid. In addition, they can be used in industrial facilities and commercial energy management systems.
Application | Key Challenges | Solutions |
Utility scale BESS (Grid connected, large scale plants) | ● Bidirectional energy flow requirement ● Load variability ● Higher harmonics ● Grid code compliance | ● Transformer windings design handle two-way energy flow ● Split windings configuration for multi inverter support ● Optimized design ensures grid compliance and voltage stability |
Hybrid power plants (Solar + Wind + BESS) | ● Unpredictable power generation ● Complex power flow management
| ● Robust core & winding design for fluctuating load conditions ● Optimized transformer impedance and voltage adaptation |
Backup power in the commercial/industrial sector | ● Smooth transition from primary power supply to batteries ● Energy resilience | ● Transformer supports bidirectional energy flow, fast switching
|
Peak demand shaving | ● Rapid load fluctuations ● High peak power demand | ● High-efficiency transformer design ● High responsitivity |
Frequency regulation & other grid services | ● Rapid frequency fluctuations ● Strict grid requirements ● High control precision | ● Support for dynamic power exchange
|
Microgrids | ● Variable load supply ● Switching between primary power and batteries ● Reliability | ● Robust design for transient loads and faults
|
Each has specific requirements and operating conditions. Daelim Transformer’s engineering team responds very quickly to inquiries and project specifications, with design recommendations and a price estimate. For standard small to medium-sized projects, the delivery time is 8-12 weeks.
The following features are adaptable and allow the transformer to be used in a variety of conditions, industries and environments:
Utility scale BESS units are commonly deployed in 2-hour and 4-hour configurations. These high-density storage systems unit typically interfaces through a dedicated step-up transformer with multiple low-voltage outputs. Such combinations provide optimized load sharing, scalability, and resilience, while addressing the demanding operating conditions of inverter-based systems.
From a design perspective, these are most often pad mounted transformers for outdoor use with robust thermal and dielectric performance. They are often supplied with features such as tap changers, surge protection and systems for monitoring temperature, pressure and oil level.
The use of durable enclosures, adequate monitoring, and multi-winding configurations ensure the compatibility of BESS transformers with fast-cycling and highly demanding grid-scale energy storage applications.
Project Type | What Client Needed | What Daelim Transformer delivered | Key Outcomes |
Utility scale grid BESS
| ● High MVA rating transformer ● OLTC regulation ● Utility interconnection ● IP56 protection level | ● 146 MVA BESS transformer ● 21-position OLTC ● Low noise (70.2 dB at 1m) transformer with IP56 protection ● IEC/AS/IEEE compliant | ● Stable and precise voltage regulation for grid support ● Reduced downtime due to weather-resistant design ● Seamless utility interconnection |
Containerised BESS transformer | ● MV connection ● Compact design ● Fast Factory Acceptance Testing ● Complied with California Electrical Code 450 | ● Pad mounted transformer ● FAT report done within 3 business days ● Complied with all required standards | ● Pad mounted design enables safe installation ● Reliable and standardized performance ● Simplified MV connection |
BESS + solar hybrid | ● Handle solar system and battery inverter on one transformer ● Suitable in harsh environmental conditions
| ● 4.4MVA/4.8 MVA BESS transformer ● Wide operating ambient temperature range ● Low energy losses ● Using oils with a low pour point | ● Integrated support for hybrid systems in one transformer ● Optimized performance ● Improved overall system efficiency ● Reduced oil viscosity issues at low temperatures |
In order for electricity to be stored in a BESS, or sent to the grid during periods of power shortage, all elements need to meet certain standards and norms. Utility interconnection approvals, financial and insurance aspects of the project require documented transformer quality. Daelim Transformer’s transformers undergo a rigorous factory acceptance program, which ensures compliance with standards, quality of manufacture, and transformer performance.
Production Capacity | Quality Assurance Programme |
Two factories with an area of over 60,000 m² . | ISO 9001:2015 across all manufacturing stages |
Transformer manufacturing capacity – 345 kV/500 MVA | No-load and load loss measurement |
300+ employees in both facilities | Lighting impulse withstand |
5000+ units exported worldwide annually | Full Factory acceptance test within 3 business days |
500+ units in stock at China/USA for fast shipment | DGA oil analysis is standard |
Complied with global standards such as ANSI / IEEE / IEC / CSA / AS / NEMA | Electromechanical tests according to valid certifications |
The success of any energy project, including the delivery of BESS transformers, depends on the quality of workmanship and safe and timely delivery. Damage in transit is one of the main reasons for project delays.
Daelim Transformer’s method of packaging and preserving transformers during transport practically eliminates this risk. The company provides the client with logistical support during transport, using both road and sea transport.
Our transformers are carefully prepared, protected, and equipped for safe transportation, ensuring they arrive on site in perfect condition and ready for operation. The process of preparing the transformer includes:
The lifespan of batteries is 10-15 years, and of BESS transformers over 20 years. With battery replacement, such a project can operate for decades. Transformer support should last throughout this period – not just after commissioning and shortly thereafter. Daelim Transformer offers end-to-end support for your BESS project, covering all stages and including:
Daelim Transformer has developed excellent BESS transformer solutions through many years of experience that ensure constant reliability in operation. We recognized the importance of supporting next-generation energy systems with advanced and efficient transformer solutions.
Send us your project specification – rated MVA or kVA, primary and secondary voltage, frequency, applicable standard, basic environmental performance and grid-code requirements. Daelim Transformer’s engineering team will get back to you with a firm-price quotation with the technical parameters of the future transformer within 48 hours.
You don’t have to wait weeks to get feedback. Our expert qualified team will review your specification and get back to you with all the necessary technical and financial details for your project.
A standard unit will work, but for a limited period. Its insulation will deteriorate faster and early failures can be expected. Daelim Transformer’s BESS transformers are designed for 20+ years of operation. They are built to withstand harmonic voltages, transient voltages, and sudden load changes
It depends on the design specifics and the size of the transformer. Standard configurations of small and medium sizes can be delivered in 8-12 weeks. Custom projects: 10-16 weeks. Large transformers are delivered in 6-8 months, while very large units require more time. Transformers with standard stock specifications can be shipped within one week.
A double-split winding transformer enables multiple PCS units to share one transformer while reducing harmonic distortion through phase-shifted winding arrangements. This can lower system complexity, reduce equipment costs, and in some cases eliminate the need for additional harmonic filters.
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