On the medium voltage crosslinked polyethylene shielding is very important, it can improve the uniformity of the electric field distribution, according to the understanding of the standard, screen is divided into nonmetal shield (conductor shielding, insulation shield), metal shielding (copper strip, copper wire).
The central pressure crosslinking cable is now used to tighten the structure of the circular conductor, which is to improve the electric field of the conductor, and on the other hand, I understand the function of blocking water.
But even with this compression method, and tiny gaps exist between conductors monofilament, is bound to cause the uniformity of electric field distribution, and stranded conductors or convenient to produce small burrs, will cause the increase of the partial discharge, caused serious breakdown.
Crosslinked conductor shielding helps to improve the defects in this area and is closely related to insulation.
Insulation shielding also reduces the air gap between the insulation and the copper belt, the uniform insulation surface electric field.
The volume resistivity of crosslinked insulation shielding is more than the standard requirement, and the increase of the power capacity is easily induced, so it is important to control the volume resistivity of raw materials.
The protective effect of the copper band shield is that it can be used as a conduit for the leakage of current through a short circuit.
Discharge pressure testing finished products, is to strip a on insulation shielding, do 8.7/10 kv cable generally end little breakdown, why 26/35 kv cable breakdown rates are high end?
And the breakdown points are at the bottom of the semi-conductor.
As the voltage increases, the electric field increases gradually.
The shielding length is not enough and the semi-conductor handle is not smooth.
The stress cone is not in place.
These are the main reasons for the head-to-head breakdown.
Processing method is stripping the insulation block length increases, according to the experience of not less than 70 cm, it is advisable to stress cone screw installed in half a conductive mouth up to 2 mm, not smooth processing available gently scrape flat glass, but it can't hurt and insulation.
What is the effect of the cable installation?
Domestic indoor outdoor terminal attachment is now in the main, the technology basically has no problem, the key is the treatment of the shield.
Processes is not good, easy to cause the terminal breakdown, the key is outer screen processing, according to relevant data shows, semi conductive mouth breakdown caused by the improper control of attachment than any other reason, because the electric field is more concentrated, semiconduction processing to smooth mouth, such as 35 kv crosslinking cable now most not stripping the shielding material.
Only with the aid of stripping knife cutting semiconductive, may be convergent is not very smooth, can use the mouth of the semiconductive thin glass arc week blew a slope, beneficial to the improvement of the electric field uniformity.
Shielding technology in the application of crosslinking cable or improved with the development of information society and constantly improve, only by constantly to discovery, can find more problems, and to verify, through practice so as to better improve the quality of products.
