Views: 222 Author: Site Editor Publish Time: 2020-12-15 Origin: Site
Electric wire, divided into bare wire, electromagnetic wire and insulated wire, is used to transmit electric energy. The bare wire has no insulation layer, including copper, aluminum flat wire, overhead stranded wire and various profiles (such as profile wire, bus bar, copper bar and aluminum bar). It is mainly used for outdoor overhead and indoor bus bars and switch boxes. How to eliminate the overhead line faults?
Line grounding can be divided into single-phase grounding, two-phase grounding and three-phase grounding. There are two kinds of grounding faults: permanent grounding and instantaneous grounding. The former is usually caused by the ground fault of the insulation breakdown conductor, while the latter is usually caused by lightning flashovers and foreign matters falling on the conductor. One of the most common is the single-phase grounding of overhead lines. We can use ground fault indicator outlets and ground fault monitors to detect ground faults.
By detecting the voltage of the circuit, the earth fault can be identified. If we want to detect the circuit quickly and efficiently, earth fault indicators and mobile monitoring cable systems will be our help.
The search of grounding circuit
The method of testing and pulling each line is generally used to determine the grounding line. The following steps shall be taken to deal with single-phase ground fault:
(1) Determine whether the single-phase grounding really occurred;
(2) Determine which phase is grounded;
(3) Find which line is grounded.
During operation, the order of opening the line is determined according to the actual conditions such as the size of the line load, the length of the line or the failure rate of the line. If the grounding signal disappears when a certain line is opened, it means that the grounding is on the line. In addition, the remote overhead line fault passage indicator and earth fault indicator tester also have the ability to find grounding lines.
For short overhead transmission lines, personnel can be arranged to conduct a comprehensive inspection along the line, but for long overhead transmission lines, the optimization method should be adopted.
Firstly, the tension pole at half of the length of the line is segmented, and the three-phase drainage line is disassembled to divide the whole line into two sections. Then, the insulation resistance of the three-phase conductor is measured at 2500V megger. According to the measurement results, it can be determined that one section of the line is grounded or both sections are grounded.
Secondly, according to the judgment results, we continue to search by segments, and we gradually narrow the search range. When the grounding range is reduced to a certain extent, personnel can be arranged to conduct comprehensive inspections along the line. In this way, time and labor can be saved and work efficiency can be improved.
For high-voltage transmission lines, in addition to line protection devices, the substation will also be equipped with accurate cable fault passage indicators, automated cable fault indicators and traveling wave fault locators. Some are also equipped with wavelet range finders. The traveling wave and wavelet distance measuring device can accurately determine the location of the grounding point, and the accuracy can reach 5km and 1-2km in general. It is very useful for fault line checking.
When overhead line grounding occurs, it must be carefully detected and judged accurately. Advanced cable fault passage indicators and accurate cable fault indicators can help us improve work efficiency.