N2 Electrical Trade Theory|The Easy Way!


3


Method In ducts


Advantages


• Easy to identify and trace a cable. • Easy to locate a fault. • Easy to repair a fault (make joints). • Easy to add cables to the same route. • Easy to replace a cable. • They are not visible (not unsightly). • Well protected against mechanical damage.


• Well protected against the elements, e.g. sun and lightning.


Buried


• Well protected against mechanical damage.


• They are not visible (not unsightly). • Chances of theft are very low. • Chances of vandalism and sabotage are low.


• Not exposed to the elements, e.g. sun and rain.


• Chances of damage by lightning are very small.


• The digging that is required is one of the biggest disadvantages.


• Difficult to install, especially in rocky areas.


• Difficult to identify and trace a cable. • Difficult to locate a fault. • Difficult to repair (make a joint). • Difficult to add a cable to the same route.


• Difficult to replace a cable. • Expensive to install (digging).


Exercise 1.1


1. Mention two methods of installing cables that you have actually seen and give an example of where you have seen each of the methods.


2. Mention four disadvantages of buried cables. 3. To what dangers are cables, suspended out in the open, exposed?


4. Mention three advantages of installing cables by suspending them in the open.


5. Mention two detrimental effects that the sun has on exposed cables.


6. What do you consider to be the biggest disadvantage of installing cables underground?


7. Mention three advantages of installing cables by burying them. 8. Mention three advantages of installing cables in ducts.


Disadvantages


• More expensive to install as the construction or purchase of the duct is expensive.


• More difficult to identify and trace a cable.


• In smaller ducts, heat build up can result in a lower rating than a cable installed in free air or buried in the ground.


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