Fault Analysis And Protection For Local Coupling Double-circuit Transmission Lines

Multi-parallel transmission lines on the same tower are the inevitable trend of power gridconstruction, while most of double-circuit transmission lines are in the local coupling form, ofwhich fault analysis and protection are the important foundation for safe and stable operationof the power grid. Due to the complex zero sequence coupling of the local couplingdouble-circuit transmission lines, its fault analysis is in a special form, what’s more,traditional protection doesn’t consider the effects of the local coupling, its protection hasdifficulty in ensure the correct action. So, this dissertation researches on decoupling method,fault analysis, characteristic of zero sequence current protection, effects of local couplingagainst zero sequence protection and protection for the local coupling double-circuittransmission lines. The main research works and results are shown as following:1. Based on decoupling theory and method for single circuit and coupling double-circuittransmission lines, this dissertation constructs the modulus voltage and current quantitiesequation with the different fault boundary conditions and the modulus voltage and currentquantities interface equation of coupling demarcation point, and then propose fault analysismethods for local coupling double-circuit transmission lines through the three-terminalelectric quantities. The proposed calculation method has the advantage of no compoundsequence networks, practicability and university. Based on the ATP/EMTP, the model oflocal coupling double-circuit transmission lines is conducted for the simulation verification.2. To research on the influence of local coupling line ground fault against the zerosequence protection, this dissertation chooses the typical local coupling double-circuittransmission lines, and then conducts the operating characteristic analysis for zero sequenceprotection based on different fault location through fault analysis method for three terminallocal coupling double-circuit transmission lines.3. Fault characteristic anaysis is conducted for the influence of local couplingdouble-circuit transmission lines against zero sequence protection, and based on the faultanalysis for three terminal local coupling double-circuit transmission lines, this dissertationestablishes the fault characteristic program of local coupling double-circuit transmission lines.With this repository, it analyses the effects of local coupling double-circuit transmission lines against zero sequence protection at different local coupling rates and system impedance ratioto display the relationship between local coupling rates, system impedance ratio and zerosequence current beyond ratio for the department of planning, operation and protection as aguide and decision role.4. Based on the operating characteristic analysis for zero sequence protection, thisdissertation proposes new programs and setting principle of the zero sequence protection forlocal coupling double-circuit transmission lines and analyses the feature of protection, thenconducts the sensitivity calibration of the new zero sequence protection. Based on theATP/EMTP, the model of local coupling double-circuit transmission lines is conducted forthe simulation verification to make sure the feasibility of the new zero sequence protection.This dissertation is supported by the National Natural Science Foundation of China(NSFC, No.51307065) and the Doctor Subject Specialized Research Foundation (No.20100172120033).