Key Technologies for 10kV Dry-type Transformers with Noise Level <55dB for Urban Substations
Urban substations are core components of the urban power distribution system, responsible for converting high-voltage power into low-voltage power to meet the electricity needs of residential areas, commercial districts, and public facilities. Due to their close proximity to urban populations, 10kV dry-type transformers used in urban substations have strict requirements on noise control, with the noise level required to be below 55dB(A). This is not only to comply with environmental protection standards but also to avoid affecting residents’ daily life. Unlike traditional dry-type transformers, those for urban substations need to balance compact structure, high reliability, and ultra-low noise. This article elaborates on the key technologies required to achieve 10kV dry-type transformers with noise levels <55dB for urban substations, covering core component optimization, vibration and noise reduction, structural design, and testing verification, providing a practical reference for engineering and technical personnel, with a total word count controlled at around 1000 words.
Core Component Optimization Technology: Suppressing Noise Sources
The noise of dry-type transformers mainly comes from the vibration of the iron core and windings, accounting for about 70%-80% of the total noise. Optimizing the design and materials of these two core components is the fundamental measure to control noise below 55dB.
1. Iron Core Noise Reduction Technology
The iron core is the primary noise source of dry-type transformers, and its noise is generated by magnetostriction—the microscopic deformation of silicon steel sheets under alternating magnetic fields. To suppress this noise, three key technologies are adopted. First, high-quality low-magnetostriction oriented silicon steel sheets (such as grade 30Q120) are selected, whose magnetic domain structure is arranged along the rolling direction, reducing micro-deformation under alternating magnetic fields and thus lowering vibration and noise. Second, the lamination process is optimized: instead of traditional straight joints, inclined or multi-stage joints are used to reduce local magnetic density fluctuations caused by sudden changes in magnetic resistance, weakening vibration amplitude. Third, the iron core is tightly clamped with through bolts and insulating sleeves, and disc springs are used at both ends of the bolts for pre-tightening, ensuring uniform pressure (0.3~0.5MPa) between laminations to avoid resonance caused by loose laminations during operation. In addition, damping paint is applied to the iron core surface to absorb vibration energy and further reduce noise propagation.
2. Winding Noise Reduction Technology
Winding noise is caused by radial and axial electromagnetic forces generated during operation. For 10kV dry-type transformers, epoxy resin cast windings are widely used, which integrate the winding into a rigid structure through curing, significantly reducing deformation under electromagnetic forces. During the casting process, glass fiber mesh cloth is embedded inside the winding to enhance its anti-vibration strength. At the same time, axial pre-tightening force (10~20kN/m²) is applied during winding to keep the winding tight during operation and reduce displacement vibration caused by electromagnetic forces. In addition, elastic insulating supports are used between the winding and the iron core to ensure uniform gaps, avoiding local stress concentration and reducing vibration transmission.
Cooling System Noise Reduction Technology: Controlling Auxiliary Noise
The cooling fan is an important auxiliary noise source of dry-type transformers. To ensure the noise level is below 55dB, low-noise cooling technology must be adopted. For 10kV dry-type transformers in urban substations, low-noise cross-flow cooling fans (such as GFDD490-120 series) are preferred, which operate with a noise level of ≤55dB at 1 meter distance. These fans adopt optimized aerodynamic design, with smooth air flow and less turbulence, effectively reducing wind noise. The fan motor uses an external rotor structure with low vibration and low noise, and high-quality ball bearings are selected to extend service life and avoid noise caused by bearing wear. In addition, the fan is controlled intelligently by a temperature controller, starting only when the transformer temperature reaches 80℃ and stopping when it drops to 70℃, reducing unnecessary noise pollution during low-load operation.
Structural and Installation Vibration Isolation Technology: Blocking Noise Transmission
Even if the noise sources are suppressed, vibration transmission will still cause noise leakage. Therefore, structural optimization and vibration isolation installation are needed to block the noise transmission path, ensuring the overall noise is below 55dB.
1. Transformer Body Structural Optimization
The transformer shell is made of high-strength steel plates (thickness ≥3mm) to enhance rigidity and avoid resonance caused by weak structure. The inner wall of the shell is lined with damping sound insulation boards (mineral wool board + damping glue layer) to absorb internal vibration and noise, preventing noise from propagating outward through the shell. Rubber buffer pads are installed between the shell and the transformer body to avoid rigid contact and reduce vibration transmission.
2. Installation Vibration Isolation Technology
The installation foundation of the transformer is designed as a large-mass concrete structure (mass ≥5 times the transformer weight) to reduce the natural frequency of the foundation, keeping it away from the main vibration frequency (100Hz) of the transformer and avoiding resonance. Vibration isolators are installed between the transformer and the foundation: rubber vibration isolators are used for small-capacity transformers (≤1000kVA) to absorb medium and high-frequency vibration, while a combination of spring vibration isolators and rubber pads is used for large-capacity transformers to isolate low-frequency vibration. During installation, the levelness deviation is controlled within 0.5‰ to avoid additional vibration caused by center of gravity offset, and all fasteners use anti-loosening nuts to prevent vibration-induced loosening.
Noise Testing and Verification Technology: Ensuring Compliance
To ensure the noise level of 10kV dry-type transformers is stably below 55dB, strict testing and verification technologies are required during the manufacturing and installation stages. Before leaving the factory, the transformer undergoes noise testing in an anechoic chamber in accordance with IEC 60076-10 and GB/T 1094.10 standards, measuring noise at multiple points around the transformer to ensure the average noise level is <55dB. Vibration acceleration testing is also performed to measure the vibration amplitude of the iron core and winding, ensuring it meets the standard requirement of ≤2.5mm/s. After on-site installation, on-site noise testing is carried out to consider the impact of the installation environment, and adjustments are made to the vibration isolators if necessary to ensure compliance with environmental noise standards.
Conclusion
Achieving 10kV dry-type transformers with noise levels <55dB for urban substations requires a systematic combination of core component optimization, cooling system noise reduction, structural vibration isolation, and testing verification technologies. By selecting low-magnetostriction silicon steel sheets, optimizing iron core and winding design, adopting low-noise cooling fans, and implementing strict vibration isolation measures, the noise source can be suppressed and the transmission path can be blocked. These technologies not only meet the environmental protection requirements of urban areas but also ensure the reliable and stable operation of the transformer. With the continuous development of urban power construction, the demand for ultra-low noise dry-type transformers will increase. Future research will focus on integrating intelligent monitoring technology to real-time monitor noise and vibration, further improving the noise control level and providing a more environmentally friendly and reliable power supply guarantee for urban substations.
