In calculating a line-line fault, the Positive and Negative Phase Sequence networks are placed in parallel, while the zero phase sequence is excluded. This configuration does not create a series circuit, as the currents in different parts of the network are not equal (i1≠i2≠if). When performing calculations, it is essential to use the per unit (p.u.) system, ensuring that all voltages, currents, and impedances are expressed in p.u. and denoted in lowercase letters.
PREREQUISITESElectrical engineers, power system analysts, and students studying fault analysis in three-phase electrical systems will benefit from this discussion.
As you said, equivalent positive and negative phase seq. networks can be placed in parallel when considering this fault. However, this doesn't produce a series circuit of all the impedances fed by emf "e" since currents in different parts of new network are generally different (i1≠i2≠if).BTW, if you calculate in p.u. system, all voltages,currents,impedances must be in p.u., and denoted in small letters. I have modified your schematic accordingly:Physicist3 said: