In the transmission and distribution lines, power cables, switch cabinets, overhead lines, etc., faults such as grounding and short circuit often occur. In order to facilitate the maintenance personnel to find the fault point, we need to install a fault indicating device in the line - overhead two remote fault indicator.
Several classifications of electric power remote fault indicators
1. Overhead line fault indicator
The sensor and the display (indicating) part are integrated into one unit, and the indicator is mechanically fixed on a certain phase line of the overhead line (including bare wires and insulated wires). It should have a communication function, configure a communication module, and return information such as faults, line current, and low battery power to the data receiving device connected to it. It should be able to load and unload with electricity, and no false alarm should be given during the loading and unloading process.
2. Panel type fault indicator
It is mainly used in supporting equipment such as cable branch boxes and ring network cabinets. It is an indicator composed of a sensor and a display unit, usually the display unit is embedded on the operation panel of the ring network cabinet and switch cabinet. The detection principle is basically the same as that of the cable-type short-circuit and cable-type ground fault indicators. The difference is that the detector detects a fault and transmits it to the host through an optical fiber cable, and sends an alarm signal through the host. The sensor and the display unit communicate by means of optical fiber or wireless, and the primary and secondary should be reliably insulated.
3. Cable type ground fault indicator
The sensor and display (indicating) part are integrated in one unit, fixed on a certain phase cable line (busbar) by mechanical means, usually installed on the indicator on the distribution equipment such as cable branch box, ring network cabinet, switch cabinet, etc. . In addition to the above requirements, a zero-sequence ground fault indicator also needs to be configured.
The function of the second remote fault indicator
Install a fault indicator on the line. When the system fails, due to the fault current in the line from the fault point to the feed point, all the fault indicators on the line from the fault point to the feed point will act. The window appears red (or flashes). Starting from the feed point, search along the line of the second remote fault indicator, and the last red (or flashing) point is the fault point.
It has a wide range of applications. It can indicate the faulty section and branch of the line at the middle section and branch entrance of the long line. Installed at the exit of the substation, it can be determined whether the fault is inside or outside the station. Installed at the high-voltage incoming line of the user's distribution transformer, it can be determined whether the fault is caused by the user. Installed at the connection between the cable and the overhead line: it can distinguish whether the fault is in the cable section. Once a fault occurs on the line, the line patrol personnel can use the alarm display of the indicator to quickly determine the fault point and eliminate the fault. It has completely changed the backward practice of blindly inspecting the line in the past, switching on and sending power in sections to find faults.
The overhead two-remote fault indicator provides a powerful tool for fault finding in the power system, and is loved by the majority of line maintenance personnel. However, at present, it must rely on manpower to check part by part from the substation, and the automation level is not high. If it can be combined with modern communication technology and computer technology, the information of the on-site fault indicator can be sent to the monitoring center (such as power distribution management system), and the various operating states of the line can be monitored in real time. Notify the on-duty personnel by means of screen display, indicate the changes in the operating status of the monitored line and confirm the location of the changes, which will further improve the fault handling capability and shorten the processing time.
Most of the current fault indicators are used in systems below 35kV, and it is difficult to use them in lines of 110kV and above. The main reason is that these ultra-high voltage lines require high insulation levels, difficult installation, and harsh electromagnetic environments. Therefore, it is necessary to consider non-contact detection. way to detect faults.