General Introduce:Crosslinked
polyethylene insulated cable is a type of cable suitable for
distribution networks and other fields, with advantages that PVC
insulated cables cannot compare. It has a simple structure, light
weight, good heat resistance, strong load capacity, non melting,
chemical corrosion resistance, and high mechanical strength.
Theory:Cross linked polyethylene
insulated cable uses chemical or physical methods to change the
cable insulated polyethylene molecule from linear molecular
structure to main network molecular structure, that is,
thermoplastic polyethylene into thermosetting crosslinked
polyethylene, thus greatly improving its heat resistance and
mechanical performance, reducing its shrinkage, making it no longer
melt after being heated, and maintaining excellent electrical
performance.
Characters:The cross-linked
polyethylene insulated cable adopts peroxide cross-linking method
to change the polyethylene molecule from linear molecular structure
to three-dimensional network structure, and from thermoplastic
material to thermosetting material. The working temperature is
raised from 70 ℃ to 90 ℃, significantly improving the current
carrying capacity of the cable. Crosslinked polyethylene insulated
cables have the following advantages:
1. Heat resistance: XLPE with a three-dimensional network structure
has excellent heat resistance. It will not decompose or carbonize
below 300 ℃, and can work at a long-term temperature of up to 90 ℃,
with a thermal life of up to 40 years.
2. Insulation performance: XLPE maintains the original good
insulation characteristics of PE, and the insulation resistance
further increases. The tangent value of its dielectric loss angle
is very small and is not significantly affected by temperature.
3. Mechanical properties: due to the establishment of new Chemical
bond between macromolecules, the hardness, rigidity, wear
resistance and impact resistance of XLPE are improved, thus making
up for the defect that PE is prone to crack due to environmental
stress.
4. Chemical resistance characteristics: XLPE has strong acid,
alkali, and oil resistance. Its combustion products are mainly
water and carbon dioxide, which pose little harm to the environment
and meet the requirements of modern fire safety.
Application:Crosslinked polyethylene
insulated cables are suitable for distribution networks, industrial
installations, or other areas that require high capacity
electricity consumption. They are used for fixed installation on
power transmission and distribution lines with a rated voltage of
6kV to 35kV at 50Hz AC, and their main function is to transmit
electrical energy.
Problems:Although cross-linked
polyethylene (XLPE) has many outstanding advantages as an
insulation material and has developed some excellent products after
years of effort, there are still some important issues that need to
be addressed. Improving voltage level and capacity is the
development direction of high-voltage DC XLPE insulated cable
products, which also puts forward corresponding technical
requirements.
From the technical point of view, the space charge generated and
accumulated by XLPE insulated cables in the process of High-voltage
direct current transmission is the most important problem that
polymer insulation materials need to face, which always limits the
application of polymer insulation materials in High-voltage direct
current cables. So, the mechanism of space charge accumulation and
the suppression of space charge accumulation are the focus of
research, including the corresponding research on the interface
properties of semiconductors and insulators in polymer insulated
cables, the interface properties of insulators, the influence of
temperature gradients on space charge generation, and the process
of space charge accumulation.
Of course, it also includes other issues: the mechanism of
insulation material aging, the long-term stability of new
materials, and the impact of partial discharge. It is not yet clear
whether the upper limit of operating voltage should be determined
by the measurement of space charge or by the threshold voltage of
electrical aging