Related Topics

‣  What can be the causes of damage to PVC cables and paper insulated cables?‣  What precaution should be taken while taken a cable through trenches in the following locations (a) Road crossing, (b) Railway crossing & (c) Crossing of water mains ?‣  What is called “Barrier joint” of cable ?‣  What is called “Heat shrinkable joint” of cable?‣  What are the procedures to be adopted for determining the types of cable faults ?‣  What is proximity effect ?‣  What is soil thermal resistivity ?‣  What are the methods of cable laying ?‣  what special cares are to be taken for storage of cable drum ?‣  What are the load conditions of an underground cable ?‣  What do you mean by thermal resistance of a single core cable ?‣  What do you mean by the term “Dielectric losses” ?‣  What is the procedure of reducing the sheath losses in sheaths of the three single core cables in a 3-phase system ?‣  What do you mean by the term “Sheath losses” ?‣  What do you mean by MIND cable and where is it used ?‣  What do you mean by XLPE cable and what are its advantages over conventional cables ?‣  What are varnished cambric insulated cables ?‣  Interview Question of Underground Cable

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What is proximity effect ?

Proximity effect means the interaction of magnetic fields associated with adjacent current carrying conductors parallel to each other causing a further redistribution of the current which likewise increases the ohmic d.c. the resistance of the conductor. Proximity effect increases with the conductor diameter and becomes maximum when the cables are practically in contact. Therefore, a correction is mainly necessary for L.T. cables of large cross section. Again this effect can also become important under the certain condition of cable installation. When cables are laid parallel to metal beams, walls etc as frequently happens in buildings or ships this effect increases the apparent impedance of these cables appreciably. Ultimately proximity effect exerts influence on the current carrying capacity of the cables.

How is the rating of a cable affected by the proximity of other cable in same trench ?

A horizontal spacing is desirable in order to reduce the effect of mutual heating. In case they close or touch one another the effect of mutual heating increases and accordingly, the current carrying capacity of cable decreases sufficiently.

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