The basic operating principle of a PV power station is to convert the DC power generated by solar panels into AC power via an inverter and then feed it into the grid. However, the AC voltage output by the inverter is usually low (e.g., 0.4kV, 0.69kV) and cannot be directly matched to medium- or high-voltage grids. The dry-type transformer performs the step-up task, raising the low-voltage AC from the inverter to a voltage level suitable for grid connection (e.g., 10kV, 11kv,20kV,22kv,33kv 35kV), thus achieving a stable connection between the PV station and the grid.
As a key component of PV power stations, dry-type transformers feature compact structure, easy installation and maintenance, small size and light weight, high operating efficiency, and low energy losses. They can raise the voltage generated by PV systems to the level required by the grid, playing a vital role in the power quality of the grid-connected system. For large-scale PV stations of 10MW and above, using a dry-type transformer for step-up grid connection is an indispensable technical link.
Dry-type transformers also play an important role in electrical isolation within PV systems. By transferring energy through electromagnetic induction, the dry-type transformer physically isolates the PV array from the grid, effectively preventing DC components and leakage currents from impacting the grid. This function is of great significance for ensuring the safe and stable operation of the grid.
The oil-free design of dry-type transformers provides inherent fire safety advantages. The coils are cast under vacuum with epoxy resin, forming a solid, integral structure that is oil-free, non-combustible, and self-extinguishing. They can operate safely in Class F (155°C) or Class H (180°C) insulation systems, greatly reducing the risk of fire.
PV power stations use a large number of power electronic devices such as inverters, which generate significant harmonic currents during operation. Harmonics can cause power quality issues and affect transformer efficiency and lifespan. High-quality dry-type transformers use optimized winding structures to effectively reduce additional losses caused by harmonics and minimize local temperature rise. Some dry-type transformers are also designed with a K-factor to meet the harmonic suppression requirements of non-linear loads, ensuring that grid-connected power quality complies with grid regulations.
PV power generation is characterized by intermittency and fluctuation, with changes in sunlight intensity causing frequent load variations. Dry-type transformers can handle such operating conditions well due to their excellent thermal stability and overload capacity. Under forced air cooling (AF) conditions, high-quality dry-type transformers can operate stably at 130% of rated capacity for extended periods, fully meeting the load characteristics of PV stations. Additionally, through optimized design and simulation verification, modern dry-type transformers offer good impedance and economic operating characteristics, satisfying the fluctuating and intermittent requirements of PV generation and ensuring safe and stable operation of large grid-connected stations.
The windings and core of a dry-type transformer are not immersed in insulating liquid; instead, they are insulated using epoxy resin casting or vacuum pressure impregnation. This design completely eliminates the safety hazards associated with traditional oil-immersed transformers, such as oil leakage and fire. The excellent sealing properties of epoxy resin protect the windings from moisture and dust, allowing stable operation in high-humidity and other harsh environments with reduced maintenance needs. The oil-free design also makes dry-type transformers more aligned with the green environmental philosophy of the PV industry – no toxic substance leakage risk, and they can be recycled after disposal.
During the 25-year operational life of a PV power station, transformer losses directly affect the overall power generation efficiency. Dry-type transformers use high-quality, high-permeability cold-rolled grain-oriented silicon steel sheets and advanced multi-step core lamination processes, significantly reducing no-load losses and load losses. Studies have shown that no-load losses of dry-type transformers can be about 10% lower than those of traditional oil-immersed transformers, and the cumulative energy efficiency advantage over a full year can lead to considerable cost savings. In international PV projects, high-quality dry-type transformers can achieve operating efficiencies as high as 99.5% under 100% load conditions, with even better performance under partial loads.
The operating environment of PV power stations is often harsh – desert sandstorms, coastal salt spray, rooftop high temperatures, etc., impose stringent requirements on transformers. The epoxy resin cast layer of dry-type transformers not only provides excellent insulation properties but also effectively protects the windings from mechanical stress and corrosive substances. The high overall strength of the windings enables them to withstand powerful short-circuit currents, resulting in high operational reliability. The oil-free, non-combustible nature of dry-type transformers further reduces the risk of accidents, making them an ideal choice for applications with strict safety requirements.
Throughout their entire life cycle, dry-type transformers do not require oil level checks or insulating oil filtration, greatly reducing maintenance costs and workload. Compared with oil-immersed transformers, the maintenance workload of dry-type transformers can be reduced by about 50%. This advantage is particularly important for PV stations located in remote areas – fewer on-site maintenance visits mean significantly lower labor costs and improved overall economic performance of the station.
Dry-type transformers are relatively compact and lightweight, making them easy to install and transport, especially suitable for the flexible deployment of distributed PV projects. In space-constrained locations such as commercial rooftops and parking canopies, the compact design of dry-type transformers offers a distinct advantage. The oil-free feature eliminates safety concerns when used in residential areas or densely populated locations, allowing PV power generation to be located closer to load centers more safely. Additionally, dry-type transformers can adapt to harsh conditions such as high temperatures and sandstorms, operating stably at altitudes up to 1000 meters and ambient temperatures ranging from -25°C to 55°C.
Jiangsu Xinhong Electrical Equipment Co., Ltd. has many years of experience in the power equipment sector, providing customized dry-type transformer solutions for PV power stations worldwide. The company’s SCB series dry-type transformers use epoxy resin vacuum casting technology, offering significant advantages in safety, reliability, energy efficiency, and environmental protection. They fully meet international energy efficiency standards and are an ideal choice for step-up grid connection in PV power stations.
The SCB13-1250/11 energy-saving dry-type transformer is a representative product from Xinhong Electrical for the new energy sector. Its rated capacity is 1250kVA, and rated voltages are 11kV/0.4kV. Key features include:
High efficiency and energy saving: High-permeability silicon steel sheets and multi-step core lamination significantly reduce no-load and load losses, meeting international premium efficiency standards and effectively reducing station operating costs.
Fire safety: Coils are vacuum-cast with flame-retardant epoxy resin, oil-free, non-combustible, and self-extinguishing, greatly reducing fire risk.
High mechanical strength: The epoxy cast layer effectively protects windings from mechanical stress and corrosion, withstanding high short-circuit currents.
Moisture and pollution resistance: The excellent sealing properties of epoxy resin allow the product to operate stably in high-humidity and harsh environments, with protection ratings up to IP23.
Low noise and green: Operating noise is significantly lower than national standards; the oil-free design eliminates leakage risks, and the product is recyclable after disposal.
Optional intelligent monitoring: Can be equipped with intelligent temperature control systems and PT100 temperature sensors for real-time monitoring of transformer operating temperature and fault alarms.
Xinhong Electrical offers dry-type transformers with a capacity range covering 30kVA to 30,000kVA, primary rated voltages up to 0.38kV to 35kV, connection groups available as Dyn11 or Yyn0, insulation classes supporting Class F (155°C) and Class H (180°C), and short-circuit impedance typically designed from 6% to 10%, fully meeting the customized requirements of PV stations of different scales. In addition, the company can provide both 50Hz and 60Hz frequency options to suit grid standards in different regions around the world. Xinhong Electrical strictly follows the CE / ISO9001 quality management system and offers comprehensive customization services, including voltage levels, impedance parameters, and dimensions, as well as professional pre-sales technical consulting and after-sales installation guidance.
When choosing between dry-type and oil-immersed transformers for a PV power station project, the specific application scenario should be considered comprehensively. For commercial rooftop PV, building-integrated PV (BIPV), residential distributed PV, and other applications where there are many people or indoor installation, dry-type transformers are undoubtedly the better choice due to their outstanding advantages in fire safety, low noise, and environmental protection. For large ground-mounted stations in open outdoor areas, oil-immersed transformers may have advantages in heat dissipation and large-capacity applications, but the safety and environmental benefits of dry-type transformers remain irreplaceable.
As the installed capacity of PV power generation continues to expand and application scenarios become increasingly diverse, the technical advantages of dry-type transformers are gaining wider recognition. Studies indicate that as many as 83% of PV power stations prefer dry-type transformers, mainly due to their higher operating efficiency, lower maintenance requirements, and superior adaptability to high-temperature environments.
Jiangsu Xinhong Electrical Equipment Co., Ltd. is committed to providing high-performance, high-reliability dry-type transformer products for PV power stations worldwide. With deep technical expertise, strict quality control, and flexible customization capabilities, Xinhong Electrical is helping to advance the global clean energy industry. For more product information or professional selection advice, please visit our website or contact our technical team – we will provide one-on-one technical consulting and customized services.
About Jiangsu Xinhong Electrical Equipment Co., Ltd.
Jiangsu Xinhong Electrical Equipment Co., Ltd. (Xinhong Electrical) is a high-tech enterprise specializing in the R&D, production, and sales of dry-type transformers, power transformers, and other electrical equipment. Our products are widely used in urban power grids, industrial and mining enterprises, renewable energy power generation, and various special applications. With excellent quality and service, we have earned the trust of customers worldwide. Adhering to the business philosophy of “quality first, customer foremost,” we continuously innovate to provide safe, efficient, and environmentally friendly power solutions for global users.
