Using Special Transformer Wiring to Improve the Three-phase Unbalance Rate of Railway System

Abstract

Because imbalanced power will cause the loss of the propulsion motor of the railway vehicle, and the increase in temperature will shorten the service life of the electric vehicle. Not only this but also increase the cost of electricity and maintenance. In the past, the industry only focused on methods to improve power quality such as load capacity, relay setting, and harmonic resolution. Now, the consider of three-phase unbalance rate (TPUR) must be applied. I propose special transformers wiring (STW) to improve the three unbalance rates and provide different transformer wiring methods. According to the IEEE Committee, in the future, power companies will need to install balanced relay stations to improve three-phase unbalance rate. The internal regulations of Taipower must be less than 4.5% (voltage unbalance rate (NPSUR) of 2.5% and motor temperature rise of 12.5%). The derivation of the transformer “three-phase unbalance rate” model is the focus of the railway system. This research is based on the model derivation of different wiring methods to improve the problem caused by the three-phase imbalance and improve the using life of the train. They pointed out that Scott, Le-Blanc, and Modified-Woodbridge, the three wiring methods can be applied to future railway system and reduce the three-phase unbalance rate. They are in line with the IEEE standard ( % P U V ) of less than 2%.