Views: 214 Author: Site Editor Publish Time: 2021-01-26 Origin: Site
The accurate fault circuit indicator is a device installed on the power line to indicate fault current, most of which can identify and indicate short-circuit fault by detecting the characteristics of short-circuit current.
The digital short circuit fault indicator is a kind of electromagnetic induction equipment which can reflect the short-circuit current passing through and show the fault sign. If it is found that the reliable fault circuit indicator from the power supply side to the fault point has a red card but the fault indicator after the fault point does not appear red card during the inspection along the line, the fault point is between the last red card point and the first non-red card point. The accurate electric wire fault indicator usually includes current detection, voltage detection, fault discrimination, fault indicator drive, fault status indication, signal output, and automatic delay reset control.
The digital electric wire fault indicator is usually installed on an overhead line, overhead cable, buried cable, or switchgear busbar, so it can detect voltage by detecting the potential gradient of space electric field and line current through electromagnetic induction.
According to the application object, reliable fault circuit indicators can be divided into three types: overhead type, cable type, and panel type.
l The sensor and display part of the overhead fault indicator is integrated into a unit, which is mechanically fixed to the overhead line. The overhead type fault indicator is generally composed of three-phase sequence fault indicators and can be loaded and unloaded on line.
l The sensor and display part of accurate cable indicator faults are integrated into a unit, which is usually installed on the distribution equipment such as cable branch box, ring main unit, and switch cabinet.
l The panel fault indicator is composed of a sensor and display unit, which usually uses optical fiber or wireless communication.
According to the communication function, the automated fault current indicator is divided into local fault indicators and communication fault indicators.
l When the local fault indicator detects the line fault, it will flip the card locally. With no communication function, the fault-finding still needs manual intervention.
l The accurate electric wire fault passage indicator with communication is composed of fault indicators and communication devices. When it detects line fault, it can not only flip the card locally or flash alarm but also transmit the fault information to the communication device through a short-distance wireless way. The communication device can send the fault information to the master station through wireless public networks or optical fiber, which can be equipped with telemetry and remote signaling functions.
According to the function of the automated cable indicator fault, it can be divided into short-circuit fault indicator, single-phase ground fault indicator, and ground short-circuit fault indicator.
l The short circuit fault indicator is a device used to indicate the current flow of short circuit fault, whose principle is to detect the fault by using the positive mutation of current and the power failure of the line. The fault can be judged by measuring the current mutation and duration in the line by electromagnetic induction method. Therefore, it is a fault detection device that adapts to the change of load current and is only related to the short-circuit current component when the fault occurs, which can greatly reduce the possibility of mis-operation.
l The single-phase ground fault indicator can be used to indicate a single-phase ground fault, which can judge whether the line has ground fault through the principle of ground detection.
l The design of the earthing and short-circuiting device takes into account the characteristics of the transmission line when the grounding and short circuits occur.