Reduction of magnetizing inrush current in traction transformer

Abstract

In 25kv ac main line traction system the traction transformer located in the engine are repeatedly switched off and on during the normal run of the train due to presence of neutral section in the contact wire. The transformer draws inrush current several times the full-load value. Its enegization creates severe power quality problem in each time. The inrush current may be reduced to the full-load value either by using point-onwave switching device or by connecting an external resistor in series with the primary circuit. The resistor is shorted within a few cycles of energization of the transformer to avoid voltage drop and losses during the steady-state operation of the transformer. Simulation results illustrate the effect of voltage and frequency variation on the production of inrush current. Only one circuit breaker with a delayed contact closing may be used for resistance switching. Index Terms--External resistor, inrush current, point-onwave switching, traction power supply, traction transformer Dr. K. P. Basu (M'99 and SM'02) received his B.E.E., M.E.E. and Ph.D.(Eng.) degrees from the Jadavpur University, Kolkata, India in 1961, 1967 and 1974 respectively. His research interest is power system operation, control, protection, and electric drives. He has authored and co-authored more than 70 journal and conference papers.

Investigation and modelling of sympathetic inrush due to transformer energization

“…The voltage is dependent on the angle of switching, α or also known as the point-on-wave switching. In [17], mathematical formulation for point-on-wave is derived. In order to study the effect of point-on-wave to the transformer sympathetic inrush, the same transformer modelling is used.…”

Research on uninterrupted power supply technology for auxiliary winding of electric locomotive when passing neutral section

“…②How to eliminate overvoltage and inrush current during the times of dynamic adjustment. Phenomenon of overvoltage and inrush current was analyzed and some solutions were proposed in papers [1]- [3]. One scheme was proposed to eliminate overvoltage and inrush current when passing neutral section by way of controlling primary current to an appropriate value before disconnecting the locomotive's main breaker [4].…”

Mitigation of NSC and Alleviate of Magnetic Inrush Currents in Indian Traction System

“…But as the motor which is a burden to the transformer do not stops completely the burden on transformer will be less (almost negligible). But still the introduces inrush can be reduced by connecting fast switching resistor [5].…”

“…The inrush can be reduced by the external resistance. The overall current passing through circuit is given by [5] 0 2 0…”

“…This type of permutation in the phases does not change the phase sequence of the system. To avoid the short circuit between the phases during the permutation an un-energized neutral section or dead zone (about 6m) [5] is provided between two consecutive sections of overhead wires energized from different phases.…”