Design And Development Of 27.5kV Railway Special Voltage Transformer

Oil-immersed type, SF6 gas insulated type and resin filled dry type voltage transformers are often used in railway electric power distribution system. However, due to system overvoltage, harmonic distortion, climate, and the unreliably of the voltage transformers, the voltage transformer failure has always been disturbing the railway’s power system, and being a treat to the property and humans. This paper studied and designed a new voltage transformer, it’s a high voltage equipment in railway electric power system, and also a critical relay protected equipment for electric power metering in railway electric power distribution system.This paper studied the principle of electromagnetic induction inside the voltage transformer. In this paper, specific designs of ferrite materials and insulation materials, and the layout of them inside the transformer are made. In this paper it is also carefully designed the layout of the high voltage winding and the inner shielding. By these means, JZFWT2-27.5 railway voltage transformer is developed in this paper. It has improved overvoltage resistance, bias tolerance, high partial discharge strength and pollution resistance. The product’s excitation has been tested by TDGC2J-30kVA voltage regulator and T24-VA voltage-ampere meter, at different voltages to validate the overvoltage performance; the product’s tolerance is validated by HE5 meter and voltage generator; the product’s partial discharge strength is tested and validated by JF-2001 partial discharge tester in high voltage isolation room; the product’s creeping distance is checked using self-adhesive tape stuck along the shortest route between high voltage and ground, to validate the pollution resistance of the product.The result showed this newly developed voltage transformer has a premium performance, with overvoltage factor 2.5, partial discharge strength≤10pC at 1.2Um; pollution resistance much higher than IV; and it can be operated reliably at 3000m above sea level. This product has great and important meanings tothe improvement of railway electric power distribution system quality level and also tothe improvement of the safety to property and human. This voltage transformer also improves the technical level of domesticvoltage transformer market.