Zero-sequence disturbance line selection protection system for neutral point ungrounded transformer substation and application of zero-sequence disturbance line selection protection system

Abstract

The invention discloses a zero-sequence disturbance line selection protection system for a neutral point ungrounded transformer substation and application of the zero-sequence disturbance line selection protection system. A primary equipment unit is used for changing a transformer substation outgoing line topology into grounding through a grounding transformer and a line selection resistor after asingle-phase earth fault occurs in the transformer substation, enhancing a zero-sequence current signal of a fault loop by adjusting a resistance value and input time of the line selection resistor,reducing an overvoltage level of a fault line and judging the fault line by utilizing the zero-sequence signal; and the primary equipment unit is connected with a secondary equipment unit, and the secondary equipment unit is used for judging the occurrence of a fault, controlling the switching of primary equipment and calculating and reporting a line selection result. According to the invention, the grounding transformer and the line selection resistor which are input in a transient state are utilized to enhance the zero-sequence current signal of the fault loop to quickly and accurately judgethe fault line; by adjusting the resistance value and the input time of the line selection resistor, the line selection accuracy is improved, and the overvoltage level of the fault line is reduced; and after the fault is removed, the operation is automatically quitted without influencing the existing circuit topology of the power distribution network.

Description

technical field [0001] The invention belongs to the technical field of power distribution equipment, and in particular relates to a zero-sequence disturbance line selection protection system for a neutral point ungrounded substation and an application thereof. Background technique [0002] For substations in the distribution network of power systems, the form of outgoing lines and the size of the capacitive current when a single-phase ground fault occurs are generally used as the judgment standard for selecting the neutral point grounding method. If the outgoing line of a substation is dominated by overhead lines, and the capacitive current does not exceed 10A, the neutral point is usually not grounded. The advantage of choosing the neutral point to be ungrounded is that when a single-phase ground fault occurs, the thermal effect caused by the ground capacitance current is not large, which can be borne by the insulation of each component of the power grid, and it can still r...

AI Technical Summary

Problems solved by technology

However, the transient line selection device generally configured in the existing neutral point ungrounded system has a low line selection accuracy, and the signal characteristics of the transient signal are most obvious only at the moment when a fault occurs. Once the line selection fails, it is difficult to re-select There is a faulty line, so manual line selection is still widely used in the actual work of the substation

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