P. Pozzobon, TRANSIENT AND STEADY-STATE SHORT-CIRCUIT CURRENTS IN RECTIFIERS FOR DC TRACTION SUPPLY, IEEE transactions on vehicular technology, 47(4), 1998, pp. 1390-1404
This paper presents some significant extension and analytical formaliz
ation of the knowledge on transient and steady-state short-circuit cur
rents in de traction systems. Electrical supply substations (ESS's) in
modern metrorail and railway de systems are equipped with 6- and 12-p
ulse diode bridge rectifiers. Large existing plants are equipped with
6-pulse converters, but the 12-pulse option is preferred in the design
of new plants in the parallel configuration. Such a converter present
s a good compromise between number and voltage/current rating of semic
onductor devices, complexity and rating of transformers, de-side volta
ge ripple, and ac-side current harmonic content. In this paper, the au
thor considers the features of 6- and 12-pulse conversion units in ter
ms of transient and steady-state short-circuit currents on zero fault
impedance. Accurate determination of the transient de short-circuit cu
rrent is important for correct rating and tuning of protection devices
and power equipment (high-speed circuit breakers, isolator snitches,
switchgears, de-bus bars, etc.). An analytical solution of the short-c
ircuit behavior is given for zero fault impedance currents: phase curr
ents of the transformer, transient short-circuit de current, approxima
te expression of the de short-circuit current, and accurate expression
of the steady-state de short-circuit current. The general calculation
method used in the paper is extensible to any conversion unit with a
double secondary transformer.