DDX1 short-circuit limiter is equivalent to a short-circuited busbar while it is up and running, load current flows through at this moment.  When the short circuit fault happens in the feeder lines, the short-circuit current iz flowing through the feeder is the sum of the short-circuit currents provided by # 1 and # 2 transformers, ie. iz=i1+i2, which far exceeds the breaking capacity of the feeder breaker. After the DDX1 short-circuit current limiter is installed on the contact line, it can be cut off instantly within 3 ~ 5 ms. It contributes to the separate operation of two-section buses and reduce the short-circuit current by about 50% caused by the feeder switch.So, the short-circuit current i1 ( or i2 ) provided for only one transformer could be controlled within the safe range of the feeder switch.  ( For the structure and principle of DDX1 short-circuit limiter, please refer to its specification ).

 The electrical diagram of the short-circuit current limiter after installation at the busbar is shown in fig. 1, and the waveform diagram of the short-circuit point current before and after installation is shown in fig. 2.  In the figure, the voltage crosses zero at the moment of short circuit, so the aperiodic component of short circuit current is the largest, and the ordinate represents the peak value of short circuit current ( the peak value of short circuit current that may occur in the system is 1.8× ×IDL≈2.5 IDL, where IDL is the effective value of rated short circuit current of the system ).

Fig. 1 application diagram of ddx1 in contact line