Analysis of Effect of Urban Mass Transit Traction on Derating of Transformers

Abstract:

Models of power supply system composed by AC and DC traction modes with 12 pulse or 24 pulse rectifiers were established by taking centralized power supply in rail transit for example in order to study the effect on derating of transformers caused by harmonic currents in different traction and rectification．The study results show that the higher proportion of DC resistance losses in the total load losses of the transformer is，the lower derating rate is；24 pulse rectifier has less effect on transformer derating than 12 pulse rectifier；the larger the traction load power is，the lower the derating rate is．The results provide reference for selection of rectifier system，traction type and the main transformer’s capacity determination in urban mass transit．

Key words:power supply type; rectifier system; harmonics; AC traction; transformer derating