low voltage cable steel armor need to be grounded?

Views: 0     Author: Site Editor     Publish Time: 2022-03-30      Origin: Site

The steel armor of the armored cable increases the mechanical strength and protects the cable from external impact damage and rat bites. It is the first choice for buried cables. 


Does the low-voltage cable steel armor need to be grounded?


1. Low voltage armored cables need to be grounded

If the low voltage armored cable is not grounded, the current passing through the cable is large enough to generate eddy currents in the armored steel tape, the steel tape will heat up, the current carrying capacity of the cable will drop, and the cable will reheat, resulting in a short circuit or burnt out of the cable.

The construction process requirements and specifications of the cable include: after the cable armored steel tape is derusted (painted), the tinned soft copper grounding wire is tightly bound on the steel tape with 2.5 square copper wire for more than 5 turns. The insulating layer is thin and can only be tied but not welded, the contact surface is coated with conductive grease, and the high-voltage cable is brazed with a soldering iron after binding.


2. Why should the steel tape armored cable be grounded?

(1) If the steel strip pierces a certain phase insulation in the middle of the cable, and the outer sheath is intact, the steel strip is in a live state, but it cannot be detected, and it is easy to cause an electric shock accident; if it is grounded, it can drive the protection device to trip. .

(2) Although the steel tape of the inner armored cable is not exposed, when the three-phase current is unbalanced, the armored layer may discharge due to the effect of the induced electromotive force, and the sheath may be burned in severe cases. When the armored layer is grounded, it is leveled with the ground potential to eliminate the discharge phenomenon.

(3) After the copper tape shield is grounded as a part of the core insulating shielding layer, on the one hand, the potential of each core shielding layer can be leveled, and on the other hand, the potential difference between the copper tape and the steel armor can be reduced to avoid the occurrence of discharge.

(4) If it is not grounded, the current passing through the cable is large enough to generate eddy currents in the armored steel tape, the steel tape will heat up, the current carrying capacity of the cable will drop, and the cable will heat up again, causing the cable to be short-circuited or burned.


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