cable news: analysis of yjv high voltage cable fault
from：guichao author：admin click： 543 addtime：2017-03-17 10:37:27
the cable is the bridge between the power supply equipment and the electrical equipment.
the application is extensive, so the fault often occurs, the following brief analysis of the reasons for the common problems of yjv high voltage cable,
according to the reasons for the breakdown of the classification can be divided into the following categories: manufacturers, construction quality reasons,
design unit design, external damage four categories.
first, manufacturers to create reasons
manufacturers according to the different parts of the reasons for the production, but also divided into the main reasons for the cable, cable connector, cable grounding system three reasons.
1, the main reason for the cable body
in the process of cable production, there are some problems, such as insulation eccentricity, uneven thickness of insulation and insulation, and impurities in insulation,
the internal and external shield has protrusions, the degree of crosslinking is not uniform, the cable is damp, the cable metal sheath is bad, etc.,
some cases may be more serious in the completion of the test or put into operation soon after the failure,
most of them exist in the cable system in the form of defects, which cause serious hidden danger to the safe operation of the cable.
2, cable connector manufacturing reasons
high voltage cable connector used to wrap, mold, molding, and other types, the need for on-site production of large workload,
and because of the limitation of the site conditions and the reasons of the manufacturing process, there will inevitably be air gap and impurity in the insulation layer,
so prone to problems. the most commonly used type in china is assembled and prefabricated.
the cable joint is divided into cable terminal joint and cable intermediate joint,
the cable joint failure usually occurs in the cable insulation fracture, because it is the site of the stress concentration,
the reasons for the failure of the cable joint due to the manufacture are the defects of the stress cone, the insulation filler and the oil leakage of the sealing ring.
3, cable grounding system
cable grounding system includes cable grounding box, cable grounding protection box (with protective layer protector), cable cross connection box, protective layer and so on.
generally prone to the problem is mainly due to poor water quality of the box seal lead to multi-point grounding, resulting in excessive metal protective current.
in addition, the parameters of the protection layer of the protective layer are unreasonable or the quality is not good, and the instability of the zinc oxide crystal is also easy to cause the damage of the protector.
two, construction quality reasons
because of the quality of the construction of high voltage cable system failure of many cases, the main reasons are the following aspects:
1, the site conditions are relatively poor, cable and connectors in the factory environment and process requirements are very high, and the construction site temperature, humidity, dust are not good control.
2, the cable construction process on the insulation surface will inevitably leave small scratches, semi conductive particles and abrasive cloth sand may also be embedded in the insulation,
in addition, during the construction of the insulation due to exposure to the air, the insulation will also be inhaled moisture, which are left to the long-term safe operation.
3, the installation is not strictly in accordance with the technical requirements of the construction process or do not take into account possible problems.
4, the completion of the use of dc withstand voltage test results in the formation of electric field caused by insulation damage.
5, due to poor sealing treatment. the intermediate joint shall be sealed with a metal copper shell plus pe or pvc insulation corrosion resistant layer,
ensure seal compaction in construction site, so the effective guarantee of the joint waterproof sealing performance.
three, design reasons
cable breakdown caused by cable heating expansion. when the load of the xlpe cable is high, the temperature of the wire core is increased, and the cable is heated and expanded,
in the tunnel, the cable is located at the top of the bracket, and the cable is very big in the long run,
to crush the facade of the stent cable sheath, cable metal sheath, into the insulating layer to cause the breakdown of the cable.