XLPE CABLE
Cross-linked polyethylene (XLPE) insulated power cable offers various advantages compared with conventional paper insulated oil-filled cable. XLPE cable has much more flexibility, is lighter weight, and does not require oil supplying system, hence less maintenance in addition to boasting smaller charging current and dielectric loss.
XLPE cable also performs in better continuous and short circuit current carrying capacity resulting from its excellent thermal characteristics. Based on these features, nowadays, XLPE cable is applied for up to 500kV extra-high voltage line.
CHARACTERISTICS OF XLPE CABLE
Polyethylene is superior in electrical characteristics and chemical resistance; however it faces a thermal instability problem and starts to melt when it reaches a temperature of 110oC.
Cross-linked polyethylene, which is the result of a molecular bonding chemical process called “cross-linking“, has solved this melting problem.
The molecular structure of cross-linked polyethylene performs excellent ozone resistance as well as outstanding stability and resistance to heat. The most famous and popular process of “cross-linking” is to blend peroxide (e.g. dicumyl peroxide) into polyethylene and extrude it around the conductor, heat it up to high temperature sufficient to achieve the peroxidation.
Comparison of characteristics between "cross-linked polyethylene" and "pure polyethylene
| Item |
Material |
| Cross-linked polyethylene |
Pure Polyethylene |
| Specific Gravity |
0.92 |
0.92 |
| Dielectric strength, kV/mm |
35-50 |
35-50 |
| Volume resistivity, -cm |
1018 |
1018 |
| Dielectric constant |
2.3 |
2.3 |
| Power factor,% |
0.03 |
0.03 |
| Tensile strength, kg/mm2 |
1.2-1.5 |
1.2-1.5 |
| Elongation, % |
500-600 |
500-700 |
| Max. operation temperature, C |
90 |
75 |
| Max. short circuit temperature, C |
250 |
150 |
| Heat deformation |
G |
F |
| Ozone resistivity |
G |
G |
| Water resistance |
F |
F |
| Oil resistivity |
E |
E |
|
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