Voltage transient management for Alternating Current trains with vacuum circuit breakers

Abstract

Alternating current power supplies and rolling stock with 25 kV (50 or 60 Hz) and 15 kV (16.7 Hz) traction systems do not have the characteristics and behaviour of a typical three-phase medium-voltage distribution system. Switching inductive loads with a vacuum circuit breaker (VCB) in MV traction systems poses familiar challenges as well as some unique challenges, such as the crossing of phase change neutral sections. Transformers represent highly inductive loads due to their iron core and, thus, the consequences of energizing and disconnecting a transformer and dealing with the energy stored in its inductance must be considered within a system context. The authors of this study consider two transient phenomena associated with switching single-phase, medium voltage, AC traction transformer loads using a VCB on railway rolling stock: (i) switching transients that occur when disconnecting a transformer, particularly if lightly loaded and (ii) pre-ignition and current inrush that occurs when energizing a transformer. Both phenomena can cause reliability problems, requiring increased system maintenance or resulting in premature failures of system components. The authors review the use of controlled switching and other state-of-the-art methods to prevent or limit voltage transients when switching a transformer load by means of a VCB. The effective application of such techniques has been demonstrated in previous research or established in practical applications by manufacturers and electrical distribution network companies.This is an open access article under the terms of the Creative Commons Attribution-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited and no modifications or adaptations are made.

Simulation of a direct torque control system in the presence of winding asymmetry in induction motor

“…In the block 'Sector Number Determination Block' the algorithm for determining the sector number (10) is implemented. In the 'Flux Observation Unit' block implemented formulas (3)-( 9) and (17).…”

“…The mathematical model of the improved DTC is based on the model (1)- (18) with the following adjustments. Coordinate transformations based on expressions (17) are performed for the voltage drop on the active resistances of the stator windings 10(d)) were obtained on the proposed simulation models for a traction motor with asymmetry of the stator windings. For symmetric regimes of the stator windings, studies on the improved model were not carried out, as in symmetric regimes the system of equation ( 20) is equal to the first two equations of system (3).…”

“…This leads to the short-term occurrence of transient processes in the traction drive system, which, in turn, causes the asymmetry of the stator current systems of the traction motors and the asymmetry of the voltage system at the output of the traction inverter. The non-stationary, non-deterministic process of changing the voltage in the catenary [15][16][17] causes voltage pulsations on the direct current link. An attempt to break down one motor causes an unevenness of the current load, which will lead to an asymmetry of the system of traction currents [18,19] when several traction motors are powered from one inverter.…”

Analysis of the Efficiency of Traction Drive Control Systems of Electric Locomotives with Asynchronous Traction Motors

“…A non-stationary, non-deterministic process of voltage variation in the catenary network [27][28][29] causes voltage pulsations in the DC link. Moreover, these voltage pulsations are of a stochastic nature.…”

Research on Transient Low-Frequency Oscillation of Electrified Railway Vehicle-Grid Coupling System

“…When the electric locomotive passes the neutral-section, there will be a complex electromagnetic transient process. When the electric locomotive adopts manual or on-board automatic passing, the on-board transformer may produce a large inrush current when it is closed without load, causing the voltage and current of the vehicle-grid coupling system to oscillate [5][6][7]. This will cause train traction blockade and feeder protection malfunction of traction substation, which seriously affects train operation safety [8][9][10][11][12].…”