To analyze and calculate the inter-line fault on double-circuit lines under non-parallel operation

an analytical method based on three sequence component method combined with fault boundary conditions and the graph of compound sequence networks is proposed. According to phase-sequence transformation

it is known that coupling exists only between zero-sequence networks for this type of lines. Then an equivalent circuit of each sequence network is developed based on the three sequence component characteristics while referring to a loosely coupled transformer model. For concise analysis of the inter-line fault

the boundary conditions and the way the graph of compound sequence networks is connected for sample and typical failure modes are summarized

which can be combined into boundary conditions and interconnection of sequence networks for a variety of inter-line faults. Thus repeated analysis of different inter-line faults is avoided. The method has a definite physical meaning and is simple in calculation and can be used to analyze inter-line faults of different parameters of two lines and incomplete-journey double-circuit lines. It is proved by simulation of PSCAD/EMTDC.