ABSTRACT
For unsymmetrical fault current calculations, the three separate networks can be connected in a certain manner, depending on the type of fault.
Unsymmetrical fault types involving one or two phases and ground are as follows:
A single line-to-ground fault
A double line-to-ground fault
A line-to-line fault
These are called shunt faults. A three-phase fault may also involve ground. The unsymmetrical series type faults are the following:
One conductor opens
Two conductors open
The broken conductors may be grounded on one side or on both sides of the break. An open conductor fault can occur due to operation of a fuse in one of the phases.
Unsymmetrical faults are more common. The most common type is a line-to-ground fault. Approximately 70% of the faults in power systems are single line-to-ground faults.
