A single-phase disconnection line selection method and system for a neutral point ungrounded system

Abstract

This application discloses a single-phase disconnection line selection method and system for a neutral point ungrounded system. Through the fundamental wave component of the line load current, the angle difference between the three phases of the current fundamental wave component is calculated, and then the first characteristic quantity is obtained. When the second If a characteristic quantity is greater than 90°, mark the line to which the first characteristic quantity meets the above conditions; if the number of lines to which the first characteristic quantity belongs is equal to 1, and the current system zero-sequence voltage is less than or equal to 20% of the system nominal voltage, continue to determine whether A single-phase disconnection fault occurs; calculate the value-added of the negative-sequence component of the load current before and after the line is marked; the value-added of the load current component before and after the marked line is approximately equal to the value-added of the negative-sequence component of the bus load current before and after marking, then select A single-phase disconnected line phase has occurred. This solves the technical problem that it is difficult to find the disconnection fault at the first time through the voltage and current of the power grid system during the power consumption process if the electricity customer fails to discover the power outage fault that may be caused by the line grounding fault.

Description

technical field [0001] The present application relates to the technical field of single-phase fault isolation of power grids, and in particular, to a method and system for selecting a single-phase disconnected line of a neutral point ungrounded system. Background technique [0002] In the power grid system, especially in the medium and low distribution network system, the single-phase disconnection fault is a common fault in the distribution line. Single-phase disconnection may be caused by many reasons such as electrical action, mechanical external force, outdated distribution lines, and bad weather. After a single-phase fault occurs, since the fault current will not suddenly increase to a large extent, the relay protection device of the substation will not act to trip the corresponding circuit breaker to interrupt the power supply, and the line will continue to operate with the disease. It is easy to develop into a phase-to-phase short circuit, and due to the lack of phas...

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Problems solved by technology

[0004] This application provides a single-phase disconnection line selection method for a neutral point ungrounded system to solve the problem of disconnection and non-ground faults. It is difficult to detect technical problems of disconnection faults at the first time through the voltage and current of the power grid system during power consumption

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