Views: 0 Author: Dada Publish Time: 2026-06-04 Origin: DaNews
In our previous article, "Oil-Immersed Transformer vs Dry-Type Transformer: How to Choose for Your Engineering Project?", we examined the core differences between the two technologies, their comparison dimensions, and a general selection framework. This article focuses specifically on photovoltaic power plants and discusses the technical details that determine whether a transformer can operate reliably in a solar system.
In a solar plant, the transformer connects the PV array to the grid. As we analyzed in the previous article, oil-immersed and dry-type transformers each have their own strengths. There is no absolute winner. However, in solar applications, the real technical risks often lie in the details: voltage level matching, harmonic tolerance, insulation coordination, and system protection. Choosing the wrong model can reduce system efficiency, increase O&M costs, or even create safety hazards. Drawing on Dada Electric's long-term manufacturing and engineering experience in renewable energy transformers, we offer this selection guide to help you make reliable and cost-effective decisions.
In the previous selection guide, we used four decision-making questions to help determine the technical direction. These principles still apply in solar scenarios, but they need to be refined based on specific site conditions:
Installation location determines the type.
As we emphasized before—"Where will it be installed?" This is the first question. Large ground-mounted plants are usually installed outdoors. Oil-immersed transformers are the mainstream choice due to their heat dissipation capacity and weather resistance. For commercial rooftop and Building-Integrated Photovoltaic (BIPV) projects, fire safety requirements are strict. Dry-type transformers are a must.
Maintenance capability affects long-term cost.
We pointed out that the maturity of the maintenance system directly impacts total life-cycle cost. Solar plants are typically designed for a 25-year service life. Remote ground-mounted plants have limited O&M resources, so the maintenance-free advantage of dry-type units is significant. Large plants with professional O&M teams can fully leverage the overload capacity and economic benefits of oil-immersed units.
Based on the different locations and functional needs within a solar plant, Dada Electric provides solutions ranging from standalone transformers to integrated power distribution systems:
This is Dada Electric's core product series, tailored for renewable energy projects. The transformer, high-voltage load switch, low-voltage distribution, and protection devices are integrated into a standardized enclosure. The pre-assembled design enables factory manufacturing and standardized testing. On site, only foundation work and external cable connections are needed, greatly reducing construction time. Integrated matching of primary and secondary equipment avoids system compatibility risks from separate procurement. With a high protection rating, these units are suitable for long-term unattended outdoor operation.
In addition to the renewable energy series, Dada Electric's general box-type substations can also be used at grid connection points or station service distribution systems in solar projects. They provide standardized, fast-delivery integrated power distribution solutions.
In the upstream solar industry supply chain—such as silicon purification, crystal pulling, and wafer slicing—Dada Electric's rectifier transformers, electric furnace transformers, and other special products provide industrial power supply assurance. This forms a complete service loop from solar manufacturing to solar power generation.
Working alongside the transformers, Dada Electric provides solar grid connection cabinets, AC distribution cabinets, DC combiner boxes, and other complete switchgear. These ensure full-link distribution protection and intelligent monitoring from the PV array to the grid connection point.
The requirements for transformers in solar plants are not exactly the same as those in standard distribution projects. Beyond capacity and voltage level, factors such as harmonics, voltage fluctuations, outdoor environmental conditions, and long-term losses all affect transformer operational stability and service life. During project selection, these issues often deserve more attention than the equipment price itself.
(1) Harmonics Cannot Be Ignored
Inverter output inevitably contains high-order harmonics. A transformer operating under harmonic currents for extended periods will experience additional iron and copper losses, localized overheating, accelerated insulation aging, and even winding deformation.
Dada Electric recommends clearly communicating the project's inverter type and harmonic content parameters to the manufacturer. Request a temperature rise calculation report for the transformer under harmonic conditions. If necessary, consider a specialized design with harmonic suppression measures or appropriately increase the transformer capacity margin. This directly determines whether the transformer can endure its 25-year design life.
(2) Voltage Fluctuation and Bidirectional Power Flow Adaptability
In self-consumption with surplus feed-in or energy storage coupled scenarios, the transformer may need to handle bidirectional power flow. Voltage fluctuates dramatically with solar irradiance intensity. This demands wider adaptability from the tap changer and insulation structure.
We recommend confirming whether the project includes energy storage or surplus feed-in requirements. Communicate tap changer selection and insulation coordination plans with the manufacturer in advance. This ensures stable transformer operation across the full voltage range.
(3) Insulation Coordination: Often Overlooked in General Applications, Critical in Solar
The insulation coordination between the DC and AC sides of a solar system requires holistic verification. The insulation levels of the transformer's primary and secondary windings, along with the neutral point grounding method, must be designed in coordination with the inverter output characteristics, cable charging capacity, and protection configuration. Otherwise, overvoltage damage may occur due to improper insulation coordination.
Therefore, at the project design stage, include the transformer in the overall insulation coordination study rather than purchasing it separately and adapting it passively afterward.
(4) Outdoor Environmental Endurance and Safety Compliance
Large ground-mounted plants are often located in extreme environments such as deserts, Gobi, or tidal flats. Day-night temperature differences can exceed 40K. The fully sealed corrugated tank structure compensates for oil volume changes through the elastic deformation of corrugated panels while keeping the internal oil isolated from outside air. This design's value is even more pronounced in solar applications.
Meanwhile, for rooftop solar, BIPV, and plants near public facilities, fire safety acceptance requirements are extremely strict. The "oil-free design, self-extinguishing" safety feature of dry-type transformers is no longer optional—it is a hard compliance requirement.
For outdoor plants, prioritize fully sealed oil-immersed transformers and confirm the protection rating. For indoor or near-occupancy projects, choose dry-type transformers as the first option and satisfy fire safety approval requirements early.
(5) Total Cost Over a 20+ Year Operating Cycle
This principle aligns with what we emphasized in the previous article, but it deserves special amplification in the solar context. Solar plants are typically planned for a 20 to 25-year operating cycle. Transformer no-load losses accumulate continuously during this period. The resulting electricity cost can far exceed the equipment purchase price. Referring to the IEC 60076-20 energy efficiency standard, selecting a higher efficiency class product typically yields a payback period of 3 to 6 years. In solar projects, this payback is more certain than in general applications because solar irradiation is relatively predictable and the power generation revenue model is more mature.
Do not focus solely on the purchase price. Request the manufacturer to provide loss parameters for different efficiency classes and a 25-year TCO comparison. Use data to support your decision.
"There is no best transformer, only the transformer that best fits your project's requirements." From standalone oil-immersed and dry-type units to integrated box-type substations and high/low voltage switchgear, Dada Electric possesses independent manufacturing capabilities for the full chain of equipment in solar plants rated 35kV and below. We do not favor any single technology. We focus solely on matching you with a reliable solution proven through engineering practice.
True reliability comes from a long-term focus on technology and rigorous quality control validated by State Grid supplier qualification certification.
No matter what stage your project is in—planning or selection—Dada Electric's application engineers are ready to provide an objective, professional life-cycle technical recommendation based on your specific project parameters.
