Features Of Dry Type Electrical Transformers

A primary distinction of dry-type power transformers lies in their ability to eliminate the fire and explosion hazards associated with transformer oil. While oil-immersed models pose significant risks if internal faults (such as short circuits or overheating) occur—potentially igniting leaked oil and triggering catastrophic blasts—dry-type units utilize Class F or H refractory insulation materials. These advanced materials are engineered to resist combustion, prevent flame propagation, and maintain structural integrity even in the event of internal malfunctions or external fire exposure. This inherent safety feature not only protects personnel and equipment but also reduces insurance premiums and regulatory compliance burdens for end-users.

Beyond fire safety, dry-type transformers eliminate the persistent issues of oil leakage and degradation that plague oil-immersed alternatives. Oil leakage can contaminate soil and water sources, leading to environmental liabilities and costly cleanup efforts, while oil aging requires regular testing, filtration, and replacement. Dry-type units’ oil-free design eliminates these concerns entirely, offering a more sustainable and low-risk solution. Additionally, this streamlined configuration translates to minimal operational and maintenance requirements: under normal operating conditions, dry-type transformers require only routine visual inspections, with no need for oil analysis, gasket replacements, or leak repairs. In many cases, they operate “maintenance-free” for years, reducing downtime and lowering long-term operational costs.

Dry-type power transformers are primarily designed for indoor installations, leveraging their compact footprint and clean operation to integrate seamlessly into industrial plants, commercial buildings, data centers, and high-rise structures. Their ability to coexist in the same room as switchgear and other electrical equipment significantly reduces the required installation area, optimizing space utilization in dense or constrained environments. For outdoor applications or harsh operating conditions—such as extreme temperatures, high humidity, or coastal regions with salt spray—manufacturers offer weatherproofed dry-type units with reinforced enclosures and corrosion-resistant components, ensuring reliable performance without compromising safety.

The oil-free design also simplifies the transformer’s mechanical structure, eliminating the need for oil conservators, safety air ducts, complex valve systems, and redundant sealing mechanisms. This reduction in components not only lowers the risk of mechanical failure but also reduces the unit’s overall weight and installation complexity. Handling and positioning become more efficient, as there is no need to manage or dispose of oil during installation, further streamlining project timelines.

Prior to installation, a rigorous unpacking and inspection process is essential to verify the transformer’s integrity and compatibility with project requirements. Begin by examining the shipping packaging for signs of damage (e.g., dents, tears, or moisture intrusion)—any breaches should be documented and reported immediately to the manufacturer. Upon unpacking, cross-verify the transformer’s nameplate data (including kVA capacity, voltage rating, phase configuration, insulation class, and frequency) with the project’s design specifications to ensure alignment.

Next, review the manufacturer’s documentation package, which should include factory test reports, wiring diagrams, installation manuals, compliance certificates (e.g., IEC 60076, ANSI C57.12.01), and a list of included spare parts. Inspect the transformer itself for external damage, such as scratches to the coil windings, deformation of the core or base, or displacement of internal components. Check electrical supports, connecting lines, and terminal blocks for signs of wear, corrosion, or looseness. Finally, examine all spare parts (e.g., bolts, connectors, gaskets) for defects or missing components, ensuring they are suitable for installation and compatible with the transformer model.

The foundation’s stability and vibration-dampening capabilities directly impact the transformer’s performance, noise levels, and lifespan. Start by inspecting the embedded steel plate of the foundation to confirm it is level within ±1mm per meter (as per industry standards) and free of gaps beneath the plate. Voids or uneven surfaces can compromise sound absorption and anti-vibration performance, leading to increased operational noise and mechanical stress. If discrepancies are found, use non-shrinking grout or shims to level the plate and eliminate gaps.

Once the foundation is verified, use heavy-duty rollers to move the transformer to the designated installation position—ensure the path is clear of obstacles and capable of supporting the unit’s weight. After positioning, remove the rollers and adjust the transformer to align precisely with the design coordinates, verifying that the installation level error meets project requirements. To prevent movement during operation (due to vibration or external forces), weld four short channel steels to the embedded steel plate at the four corners of the transformer base. This securement method ensures the unit remains stable over its operational lifecycle.

Proper wiring is critical to ensuring electrical safety, minimizing mechanical stress, and optimizing the transformer’s performance. During wiring, adhere strictly to minimum clearance requirements between live components and between live parts and ground—these distances are specified by local electrical codes and industry standards (e.g., IEC 60664 for low-voltage systems) and vary based on voltage rating. Special attention must be paid to the distance between cables and high-voltage coils, as insufficient clearance can lead to arcing, insulation breakdown, or premature failure.

High-current low-voltage busbars should be supported independently using dedicated brackets or insulators—direct pressure on transformer terminals is prohibited, as it can exert excessive mechanical tension and torque, damaging terminal blocks or coil windings. For applications with operating currents exceeding 1,000 A, a flexible connection (e.g., copper braids, flexible busbars, or laminated conductors) must be installed between the busbar and the transformer terminal. This flexible joint compensates for thermal expansion and contraction of the conductor during temperature fluctuations, while isolating the transformer from busbar-induced vibrations—preventing long-term mechanical fatigue and electrical faults.

Reliable grounding is a non-negotiable safety requirement for dry-type transformers, protecting personnel from electric shock and equipment from damage due to fault currents. The transformer’s primary grounding point is located on the low-voltage side base, featuring a dedicated grounding bolt marked with a standard grounding symbol (⚡) for easy identification. This bolt must be securely connected to the facility’s protective grounding system using a conductor of appropriate cross-sectional area (typically specified by local codes, e.g., ≥16 mm² for copper conductors in low-voltage systems), ensuring low impedance and effective fault current dissipation.

If the transformer is equipped with an enclosure, the casing must be bonded to the grounding system to eliminate potential touch voltages. For low-voltage systems utilizing a three-phase four-wire configuration, the neutral wire should be reliably connected to the grounding system—this configuration enhances fault detection, stabilizes line voltages, and provides a path for unbalanced currents, improving overall system safety and performance. All grounding connections should be tightened to the manufacturer’s specified torque and inspected regularly to prevent loosening due to vibration.

A comprehensive pre-operational check is mandatory before energizing the dry-type transformer, mitigating the risk of startup failures or safety hazards. Begin by inspecting all fasteners (including coil clamps, terminal bolts, base fixings, and grounding connections) for tightness—vibrations during transit or handling can loosen components, leading to electrical arcing, mechanical damage, or noise issues. Verify that all electrical connections are correct, secure, and compliant with the wiring diagram, paying close attention to phase alignment, terminal torque specifications, and conductor insulation integrity.

Recheck the insulation clearance between live parts and between live components and ground to ensure compliance with industry standards, as deviations can result in insulation breakdown under load. Remove any foreign objects (e.g., tools, packaging materials, dust, or debris) from the transformer’s vicinity and coil surfaces—debris can trap heat, cause short circuits, or interfere with natural convection cooling. Finally, clean the coil windings using a dry, lint-free cloth or compressed air (at low pressure, ≤5 bar) to remove dust or contaminants, ensuring optimal heat dissipation and electrical performance. Once all checks are completed and any issues are resolved, the transformer is ready for commissioning and integration into the electrical system.