ADVANTAGES OF SHIELDED CABLES

ADVANTAGES OF SHIELDED CABLES

What are the known advantages of using shielded cables?

Electrical insulation surrounding a conductor creates a capacitor when the conductor is electrically energized. Thus, all insulated conductors are capacitors.

In the majority of non-shielded cable systems, thecable surface makes intermittent contact with an electrical ground. Where intimate contact with this ground is not made, the intervening air spaces also act primarily as capacitors in ac circuits and as resistors in dc circuits. This forms a series of cable dielectric and air dielectric. Voltage across this circuit varies along the length of the cable depending on the voltage across the air gap. The cable surface becomes a floating voltage point in a voltage divider. This floating point voltage can vary considerably, depending on the cable design and the characteristics of the air gap. If the voltage is high enough, the cable surface can experience detrimental surface tracking of arcing discharges to electrical ground. The cable surface can also become potentially hazardous causing an electrical shock if contacted by field personnel.

Shielding the cable insulation surface and grounding of this shielding eliminates tracking and arcing discharges. The grounding of this shield prevents the accumulation of an electrical potential on the surface of the cable that could be hazardous to any individual that comes into contact with the cable surface.

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