Oil-immersed Transformer

As a core power conversion device in the power system, the oil-immersed transformers developed and produced by our factory adopt the core design concept of “high efficiency & energy saving, stability & durability, and safety & reliability”, and are widely suitable for power distribution needs in multiple scenarios such as industrial, civil, and power transmission applications.

I. Technical Principles and Core Structure

1. Working Principle:

Oil-immersed transformers are based on the principle of electromagnetic induction. The iron core forms a magnetic circuit, and the windings realize electric energy conversion. Insulating oil, as a cooling medium, takes away the heat generated by the iron core and windings through natural convection or forced circulation, while providing electrical insulation performance.

2. Key Components:

① Iron core: It is formed by laminating high-magnetic-conductivity silicon steel sheets. The three-dimensional wound core structure can reduce magnetic resistance and noise, and improve energy efficiency.
② Windings: High-voltage windings usually use paper-insulated flat wires, and low-voltage windings can use copper foil. They are concentrically sleeved on the iron core, and the electric field distribution is optimized through the oil-paper barrier insulation structure.
③ Oil tank and cooling system: The corrugated oil tank design expands the heat dissipation area. Combined with cooling methods such as oil-immersed self-cooling, air cooling, and forced oil circulation, it meets the requirements of different capacities.
④ Intelligent monitoring device: It integrates temperature, oil level, and pressure sensors (such as Qualitrol 506 VTM) to realize real-time data collection and remote monitoring, and support predictive maintenance.
⑤ Safety protection equipment: Gas relays (gas protection), pressure relief valves, etc., are used for early warning of internal faults and explosion protection.

II. Cooling Methods and Applicable Scenarios

1. Common Cooling Methods:

① Oil-immersed self-cooling (ONAN): Relies on the natural convection of oil, suitable for small-capacity distribution transformers below 1000kVA, such as rural power grids.
② Oil-immersed air-cooling (ONAF): Adds fans to enhance heat dissipation, suitable for medium-capacity transformers with 1000–5000kVA, such as power supply for urban residential communities.
③ Forced oil circulation air-cooling / water-cooling (OFAF/OFW): Accelerates oil circulation via oil pumps and is combined with air-cooled or water-cooled radiators, suitable for large-capacity main transformers above 5000kVA, such as substations and hydropower stations.
④ Multi-mode cooling system: Combines ion wind heat dissipation and water evaporation cooling, dynamically adjusts cooling strategies based on load, and reduces energy consumption and noise.

2. Application Fields:

① Power transmission and distribution: Main transformers in ultra-high voltage (UHV) / extra-high voltage (EHV) transmission lines, such as the UHV projects of State Grid.
② New energy grid connection: Step-up transformers supporting wind power and photovoltaic power stations (e.g., Hitachi Energy’s WindSTAR technology), meeting the high-reliability requirements of offshore wind power.
③ Industrial and urban power supply: Distribution transformers for high-energy-consuming industries like steel and chemical engineering, as well as main substations for rail transit.