Development and Application of Container-Type Low-Frequency Heating Device for Ultra-High Voltage Transformers

With the increase of voltage level and capacity, the on-site heating and drying process of damp transformer would face with new challenges. Among various heating methods currently adopted, the low-frequency heating method has attracted lots of attention owing to its simple structure and high heating efficiency, without insulation damage to the transformer. However, the device is lack of systematic design. Given that, this paper systematically introduces the design principle and scheme of the low-frequency heating source unit for ultra-high-voltage transformers. A container-type, on-site low-frequency heating power apparatus for ultra-High voltage transformer is developed. It can quickly switch between single-phase system and three-phase system, with the maximum heating power reaching 1600 kW and the frequency being continuously adjustable from 0.1 to 5 Hz. The on-site experiment results showed that the design parameters met the requirements, the insulation level of treated transformer recovered well, which provides a reference of on-site drying process for ultra-high-voltage transformers.