Small reactance value choose method during ultrahigh voltage autotransformer neutral point grounding in small reactance mode

Abstract

The invention discloses a small reactance value choose method during ultrahigh voltage autotransformer neutral point grounding in a small reactance mode. According to the principle that during neutral point grounding through an electric reactor, the ratio of the reactance value Xn of the neutral point to the zero-sequence reactance value X0 of a transformer is less than or equal to 1 / 3, according to the symmetrical component analytical method and specific boundary conditions of a dissymmetric short-circuit, by means of a BPA short-circuit current calculation procedure, a high-voltage side bus and a low-voltage side bus of a ultrahigh voltage autotransformer in a transformer substation are subjected to one-phase grounded short-circuit current calculation to choose a suitable reactance value, during the neutral point grounding through the electric reactor, the ratio of the reactance value Xn of the neutral point to the zero-sequence reactance value X0 of the transformer is less than or equal to 1 / 3, namely, Xn / X0<=1 / 3, the guarantee is provided for the reliability of monitoring the normal operation during the autotransformer neutral point grounding in a small reactance mode, and the wide practical significance is achieved.

Description

technical field [0001] The invention belongs to the technical field of power transmission and transformation equipment. Further, the invention is used for a method for limiting the unbalanced grounding short-circuit current capability of an ultra-high voltage AC power transmission system. More specifically, the invention relates to an ultra-high voltage autotransformer neutral The technical field of the selection method of the small impedance resistance value when the point small impedance is grounded. Background technique [0002] By the end of 2013, Xinjiang Power Grid has built 8 750kv lines with a total length of 2008.825km, and 270 220kv lines with a total length of about 14933.40km. Xinjiang power grid has built 5 750kv substations, 5 main transformers with a total transformation capacity of 7000MVA, and 95 220kv substations with 173 main transformers with a total transformation capacity of 24097MVA. From 2013 to 2014, Dabancheng and Yazhong 750kv substations will be ...

AI Technical Summary

Problems solved by technology

From 2013 to 2014, Dabancheng and Yazhong 750kv substations will be completed, Wubei and Fenghuang expansion No. 2 main transformers will be completed, the grid will be further strengthened, and the load will increase

[0004] It can be seen that in the field of current restrictions on unbalanced grounding short-circuit currents in ultra-high voltage AC transmission systems, the neutral point of 220 kV and above transformers is usually directly grounded, and the neutral point is an abnormal working state , after the neutral point is connected with a small reactance in series, the zero-sequence reactance of the main transformer will change, and the overvoltage level at the neutral point of the main transformer may exceed its autotransformer under power frequency overvoltage, operation overvoltage, and lightning overvoltage. Neutral point insulation, there is no systematic calculation and verification method at present

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