Single-phase broken-line selection-line method and system of isolated neutral system

Abstract

The invention discloses the single-phase broken-line selection-line method and system of an isolated neutral system. The method comprises: through a line load current fundamental component, calculating and acquiring an angular difference among the three phases of the current fundamental component, and then acquiring a first characteristic quantity; when the first characteristic quantity is greaterthan 90 degree, marking a line where the first characteristic quantity belongs and which satisfies the above condition; if the number of lines where the first characteristic quantity belongs is equalto 1, and a current system zero sequence voltage is less than or equal to 20% of a system nominal voltage, continuously determining whether a single-phase broken-line fault occurs; calculating the increment of the load current negative sequence component of the line before and after marking; and when the increment of the load current component of the line before and after marking is approximatelyequal to the increment of a bus load current negative load component before and after marking, selecting a line phase where a single-phase broken line is generated. A problem that if a power customerfails to find a power failure fault which may occur together with a line grounding fault, a broken line fault is difficult to find at first time through the voltage, the current and the like of a grid system during a power consumption process is solved.

Description

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

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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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