Break-variable direction protection method based on zero sequence impedance

Abstract

The invention discloses a break-variable direction protection method based on zero sequence impedance. The method comprises the steps of firstly constructing an electromagnetic transient model of a specified extra-high voltage layered access system in a PSCAD simulation platform; according to the electromagnetic transient model, analyzing the positive and negative zero-sequence impedance characteristics of a back-side direct current system when phase change fails; according to the protection characteristics of a break-variable direction component, combining with the obtained positive and negative zero-sequence impedance characteristics of the back-side direct current system to obtain the characteristics of power transmission line break-variable direction protection of an alternating current system; for the characteristics of the power transmission line break-variable direction protection of the alternating current system, combining with the zero-sequence impedance characteristics to design a break-variable direction protection means based on the zero sequence impedance. The method fully considers the influence of direct current layered access, can accurately locate the grounding fault location of the alternating current system when the phase change of the direct current system occurs.

Description

technical field [0001] The invention relates to the technical field of AC and DC power grid systems, in particular to a zero-sequence impedance-based mutation direction protection method. Background technique [0002] At present, there is serious spatial heterogeneity between my country's energy consumption and resource endowment. Large-scale, long-distance power transmission requirements have promoted the continuous construction and development of EHVDC projects. At present, East China and South China have formed multi-infeed In the DC system, the supporting capacity of the receiving-end power grid is facing a severe test. In order to solve this problem from the perspective of the grid structure, domestic scholars took the lead in proposing a method of connecting UHV DC to the AC grid in layers, that is, the high-end and low-end DC inverter stations The converters are respectively connected to the 500kV / 1000kV receiving end power grid through the converter transformer. [00...

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Problems solved by technology

[0003] There are still relatively few studies on this new model, mainly focusing on the introduction of the hierarchical access system, the applicability of the multi-infeed layered short-circuit ratio, the overall design of the DC control system, and the coordinated control of power. Compared with feeding DC, the topological structure of the hierarchical hybrid system at the receiving end is more complex, and the coupling between the AC and DC systems is more serious. The interactive influence between the hybrid systems at the receiving end may lead to cascading failures. The crux of the status quo of "strong straight and weak traffic" in the power grid

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