Method for calculating cross-voltage fault current of mixed-voltage double-line single phase crossing single phase on same tower

Abstract

The invention discloses a method for calculating cross-voltage fault current of mixed-voltage double-line single phase crossing single phase on same tower. The method comprises the following steps of respectively calculating positive and negative sequence impedances and positive and negative sequence networks of two power distribution systems with different voltage classes which are reduced to a fault port; measuring a double-line zero sequence constant network between the two power distribution systems with different voltage classes; according to the double-line zero sequence constant network, calculating and unifying an equivalent zero sequence network of the two power distribution systems with different voltage classes; according to the positive and negative sequence networks and the equivalent zero sequence network, combining into a composite sequence network diagram of the two power distribution systems with different voltage classes; according to the positive and negative sequence impedances, calculating the boundary condition of the cross-voltage grounding fault of single phase crossing single phase; according to the composite sequence network diagram and the boundary condition, calculating the fault current. The method has the advantages that by utilizing the double-port network theory, the calculating accuracy of the cross-voltage fault of the mixed-voltage double-line on same tower is guaranteed, the high-order matrix operation is avoided, and the calculation is simple and reliable.

Description

technical field [0001] The invention belongs to the field of line relay protection, and in particular relates to a fault current calculation method when a single-phase cross-single-phase grounding fault occurs in a mixed-voltage, same-tower, double-circuit line strong current and weak magnetic field system. Background technique [0002] my country's economy is developing rapidly, and land resources are becoming increasingly scarce. There is an urgent need for power transmission technologies with strong transmission capacity, less land occupation, and full utilization of resources. The multi-circuit power transmission technology on the same tower emerged as the times require. The multi-circuit transmission lines share the tower, the required outlet corridor is narrow, the construction speed is fast, and the investment is saved. In order to increase the transmission capacity per unit area of ​​transmission line corridors, it has become an inevitable trend in the development of...

AI Technical Summary

Problems solved by technology

[0004] When a cross-voltage fault occurs in a strong current and weak magnetic field system with mixed voltage and double circuit lines on the same tower, consider the zero-sequence mutual inductance of two lines with different voltage levels. The zero-sequence network of two lines with different voltage levels cannot be drawn separately. Contact, the positive and negative sequence networks of two lines with different voltage levels cannot be drawn separately, and a unified composite sequence network diagram cannot be synthesized through fault boundary conditions, that is, the classic sequence network diagram analysis method cannot be directly used

The traditional six-sequence component method is only suitable for the same-voltage level system with completely symmetrical line parameters, and the cross-voltage level system cannot be applied due to the asymmetry of parameters. Some scholars have proposed an improved six-sequence component method. The matrix order is still too high, resulting in complex calculations.

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