Power cables are laid underground. Once a fault occurs, it is very difficult to find. It is a necessary skill for an excellent electrician to accurately and quickly find the cable fault. Shentong Cable has found 5 common faults of power cables for everyone, with detection methods, all summarized by the old electrician, very practical, it is recommended to collect!
The five common faults of power cables are:
1. Mechanical injury
A large proportion of cable accidents caused by mechanical damage. There are four reasons for mechanical damage. One is the cable damage caused by excessive traction and bending during installation; the second is construction on the path where the cable is installed, resulting in external force damage to the cable; the third is the cable damage caused by the vibration and impact of vehicles on the road; the fourth is land subsidence, etc. Natural phenomena cause cable damage.
2. Chemical corrosion
When ACSR conductor is running, the current will cause the cable insulation to generate a lot of heat. The harsh environment will change the physical properties of the cable insulation, causing the cable to be corroded, causing pitting, perforation or even cracking, and causing failure.
3. Insulation aging
The cables installed in densely populated places, unventilated places, and places close to heating pipes are overheated, causing the cables to be overloaded and overloaded, resulting in reduced insulation.
4. Cable quality issues
Poor selection of cable materials, rough production, uneven thickness, poor waterproofness, storage and imperfect sealing during transportation can cause cable dampness and cable failure.
5. Long-term overload
ForOverhead ACSR Cable 336.4 MCMthat have been operating at high currents for a long time, the overloaded operation will cause excessive heat in the cable itself, and the impact of external forces such as thunder and lightning will cause the cable to malfunction.
After summarizing the common fault points of the cable, before introducing the detection method, the following issues should be recorded:
Cable burying situation: check the cable’s bending radius, path direction, check whether the cable has abnormal laying depth or special protective measures, such as pipe, steel plate, pipe, etc., pay special attention to finding the name of the cable laying person here In order to obtain important clues.
Cable surrounding environment: check whether there are small rocks in the soil, check whether there is construction near the cable, whether there is new excavation, pile driving or buried pipe nearby. Check the pH of the soil, whether there are corrosive components, and whether there is a chemical plant near the cable.
Cable operation and verification: Check the temperature and load of the cable, and verify the value of the cable test voltage, insulation resistance and leakage current.
After recording the above content, we began to introduce the detection methods of cable detection in detail, which are divided into the following categories:
Classical bridge method: also known as high-voltage bridge and low-voltage bridge. Find the fault by calculating the distance between the bridge wall balance adjustment data and the total length of the cable.
Low-voltage pulse method: Transmit high-frequency low-voltage pulses into the cable. When the pulse propagates, electromagnetic waves will be reflected when it encounters a fault. The fault is judged by the reflected pulse signal received by the detection instrument.
DC flashover method: Use DC voltage to break down the fault point. At this time, the fault point will flashover. The distance between the detection point and the fault point can be obtained by measuring the wave.