Earthing methods and metallic sheath types for xlpe power cables

Earthing Methods and Metallic Sheath Types For XLPE Power Cables

Power cables range includes high voltage XLPE power cables that have a metallic sheath, along which a voltage is induced as an operating current function. Manufacturers of power cables bond the both cable ends sufficiently to the earthing system to handle this induced voltage. There are some earthing methods they use for power cables, such as: ďƒź Both end bonding ďƒź Single end bonding ďƒź Cross bonding

Both end bonding Both ends of the cable sheath are linked to the system earth. Manufacturers of power cables apply this method because it is safe and secure since there is no standing voltages occurrence at the cable ends.

Single end bonding One end of the cable sheath is linked to the system earth, so that the standing voltage appears at the open end (other end). To ensure security requirements, it is necessary to protect the open end of the cable sheath with a surge arrester. The component surge arrester is intended to deflect switching and atmospheric surges.

Cross bonding Manufacturers use this method for longer route lengths where joints are needed because of limited cable delivery length. Cross bonding system includes three equal sections with cyclic sheath that is crossing after each section.

What types of metallic sheaths are available?

The metallic sheath of XLPE power cables need to meet certain electrical requirements and manufacturers need to take care of it. Some electrical requirements are as under:    

Conducting the earth fault current Limitation of the radial electrostatic field Returning the capacitive charging current Shielding electromagnetic field

XLPE power cables designed for high voltage are more sensitive to moisture ingression. The metallic sheath has to serve feature of radial moisture barrier. There are methods to prevent water and moisture entering into the cable and travelling across the length. Solutions for closed metallic sheathes can be sorted on the basis of welding, gluing, or extruding.

Some sheath layouts available at power cable manufacturers are as under:      

Aluminum laminated sheath with copper wire screen Aluminum laminated sheath with copper wire screen and integrated fibers Copper laminated sheath with copper wire screen Copper corrugated sheath Lead sheath Lead sheath with copper wire screen

All these sheath types are used for distinct applications. Let’s learn in short:  Aluminum laminated sheath with copper wire screen and integrated fibers is applied in tunnels, ducts or trenches.  Copper laminated sheath with copper wire screen is also installed in tunnels, ducts, or trenches.  Copper corrugated sheath is applied in vertical shafts  Lead sheath and lead sheath with copper wire screen are often applied in soil

Source: Earthing Methods and Metallic Sheath Types For XLPE Power Cables