Jack knowledge about cable:knowledge of high voltage cable

During electric power transmission transmission, the higher the voltage, the less the loss of power! With the development of insulating materials and technology, and now has a large number of high-voltage cable production and extensive application! Here jack'll tell you about the structure of high-voltage cables, usage characteristics, Construction and other knowledge!

High voltage cable is a power cable, means for transmitting the power cable 10KV-35KV (1KV = 1000V) between the power transmission and more used in the main road.

The structure of high-voltage cables

High voltage cable from the inside to the outside components include: conductor, insulation, inner sheath, fillers (armored), external insulation. Of course, armored high-voltage underground cables are mainly used, can resist the oppression of high intensity on the ground, while preventing other external damage.

High-voltage cable to use features

The product is suitable for AC rated voltage 35KV and below for power transmission and distribution lines with a fixed set granary, the maximum long-term working temperature of conductor 90 degrees, short circuit (the longest time not to exceed 5S), the cable conductor maximum temperature does not exceed 250 degrees.

Construction

Like other power cables, high-voltage cables have the structural elements of one or more conductors, insulation, and a protective jacket. High-voltage cables differ from lower-voltage cables in that they have additional internal layers in the insulation jacket to control the electric field around the conductor.

For circuits operating at or above 2,000 volts between conductors, a conductive shield may surround each insulated conductor. This equalizes electrical stress on the cable insulation. This technique was patented by Martin Hochstadter in 1916;[1] the shield is sometimes called a Hochstadter shield. The individual conductor shields of a cable are connected to earth ground at the ends of the shield, and at splices. Stress relief cones are applied at the shield ends.

Cables for power distribution of 10 kV or higher may be insulated with oil and paper, and are run in a rigid steel pipe, semi-rigid aluminum or lead sheath. For higher voltages the oil may be kept under pressure to prevent formation of voids that would allow partial discharges within the cable insulation.

Sebastian Ziani de Ferranti was the first to demonstrate in 1887 that carefully dried and prepared paper could form satisfactory cable insulation at 11,000 volts. Previously paper-insulated cable had only been applied for low-voltage telegraph and telephone circuits. An extruded lead sheath over the paper cable was required to ensure that the paper remained absolutely dry.

Vulcanized rubber was patented by Charles Goodyear in 1844, but it was not applied to cable insulation until the 1880s, when it was used for lighting circuits.Rubber-insulated cable was used for 11,000 volt circuits in 1897 installed for the Niagara Falls Power Generation project.

Mass-impregnated paper-insulated medium voltage cables were commercially practical by 1895. During World War II several varieties of synthetic rubber and polyethylene insulation were applied to cables.Modern high-voltage cables use polymers or polyethylene, including (XLPE) for insulation.