Research On Current Balance Protection And Phase-by-phase Reclosure Of Double-circuit Transmission Lines

The double-circuit transmission lines on the same pole have the advantages of narrow outlet corridor,large transmission capacity and reliable operation,so they have been widely used in power systems.However,due to the problem of zero-sequence mutual inductance and cross-line faults in the double-circuit line,the protection based on single-circuit configuration and the methods of the single-circuit to discriminate between transient from permanent fault cannot accurately reflect the fault condition when applied to double-circuit lines,so it is necessary to study the protection and adaptive reclosure of double-circuit transmission lines on the same pole.Firstly,for the problem that traditional current balance protection on double-circuit transmission line can not react to the interline fault,a current balance protection based on the same directional component current phase selection is proposed.First,the fault phase selection is realized by using the incremental quantity of the same directional component current.The discriminant method of two-phase short circuit and three-phase short circuit is provided.Then,the ratio of the opposite direction component current to same directional component current is used to judge whether the fault phase is interline fault.For the interline fault phase,the fault location is determined by distance protection of singe-circuit transmission line.For singe-circuit transmission line fault phase,the fault line selection is determined by the magnitude of the same-name-phase.The six-sequence fault components is used to analyze the phase selection criterion and the protection criterion under different fault types,and a specific p,.rotection process is proposed.Secondly,the phase-by-phase reclosure of parallel double-circuit lines on the same pole with shunt reactors is studied.The current frequency characteristics of shunt reactors under different fault properties are studied.Considering the influence of the inter-line coupling capacitances,the equivalent circuit models of double-circuit operation,single-circuit operation and one-circuit maintenance are established.The free oscillation frequency of the shunt reactor current is analyzed by the circuit law.The results show that the free oscillation frequency of the shunt reactor current is affected by the type and nature of fault,and the mode of operation.The ATP-EMTP simulation verifies the correctness of the analysis conclusion.The proposed protection scheme can reflect the interline fault.The frequency characterstic of the shunt reactor current can be used to determine the fault characteristics of the adaptive reclosing.