Research On Relay Protection Method Of Asymmetry-parameter Four-parallel Transmission Lines On The Same Tower

With the rapid application of the four circuit power transmission technology,higher requirements are put forward for the relay protection of the four-parallel transmission lines on the same tower(FTLST).This paper does a lot of research on FTLST and the major achievements are as follows:(1)Put forward the asymmetric phase-line parameters model,and put forward the expansion method of four zero-sequence components to resolve the model.This parameter model has the characteristics of the phase parameters and line parameters both being asymmetric,which makes it more broad and general.The expansion method of four zero-sequence components realizes the completely decoupling of the forementioned parameter model.(2)Put forward the grounding distance protection scheme based on complex field analysis.Assuming that the transient resistance of short circuit fault if pure resistance load,derive the distance measurement algorithm by complex field analyzing of partially-decouped sequence component;Propose the three-staged adjusting algorithm and action logic.(3)Put forward a line and phase selection scheme based on sequence component.In terms of the ‘Line selection by each phase' design principle,realize the correct judgement of fault type,fault line and fault phase by completely decoupling and fault analysis of asymmetric-parameter FTLST.(4)Put forward the pilot protection scheme based on distance measurement by common-sequence component.Derive three kind of two-end distance measurement algorithm by sequence network analysis.Combine the forementioned algorithms to conduct compounded fault judgement and design a pilot protection.At last,summarize the research work and make forecast.