35kV Oil-Immersed Power Transformer: Technical Overview A 35kV oil-immersed power transformer is a critical component in electrical power distribution and transmission systems, designed to step up or step down voltages efficiently while ensuring reliable operation. These transformers are widely used in substations, industrial facilities, and renewable energy projects due to their robust construction, high efficiency, and ability to handle medium-voltage applications. Design and Construction The transformer consists of a magnetic core made of laminated silicon steel sheets to minimize eddy current losses. The primary and secondary windings, typically constructed from copper or aluminum, are wound around the core and insulated to withstand electrical stresses. The entire assembly is housed in a sealed tank filled with mineral oil, which serves multiple purposes: 1. Insulation: The oil provides dielectric strength, preventing arcing between windings and the grounded tank. 2. Cooling: Oil circulates naturally or via forced cooling systems (e.g., radiators or fans) to dissipate heat generated during operation. 3. Protection: Oil acts as a barrier against moisture and contaminants, prolonging the transformer’s lifespan. Key Features - Voltage Rating: Designed for 35kV primary/secondary voltages, adaptable to various configurations (e.g., Delta-Wye). - Efficiency: High efficiency (typically >98%) due to low core and copper losses. - Cooling Methods: ONAN (Oil Natural Air Natural) or ONAF (Oil Natural Air Forced) cooling for optimal thermal management. - Safety: Equipped with a conservator tank, breather, Buchholz relay, and pressure relief devices to monitor oil levels and detect internal faults. - Tap Changer: Off-load or on-load tap changers (OLTC) adjust voltage ratios to compensate for grid fluctuations. Applications - Grid Substations: Steps down 35kV to lower distribution voltages (e.g., 11kV or 6.6kV). - Industrial Plants: Powers heavy machinery and processes requiring medium-voltage supply. - Renewable Energy: Integrates with solar/wind farms to connect to the grid. Maintenance and Standards Regular oil testing (dielectric strength, acidity, dissolved gas analysis) and visual inspections ensure compliance with IEC 60076 or IEEE standards. Proper installation, grounding, and lightning protection are essential for safety. Advantages Over Dry-Type Transformers - Higher overload capacity and better heat dissipation. - Longer operational life (25–30 years) with proper maintenance. - Cost-effective for high-power applications. In summary, the 35kV oil-immersed transformer is a versatile, durable solution for medium-voltage power systems, balancing performance, safety, and efficiency. Its design prioritizes reliability, making it indispensable in modern electrical infrastructure.