ETO ETO Exam papers 📅 Sep 2024

Exam Question

With reference to a three-phase switchboard electrical distribution system:

(a) State the advantages of an insulated neutral system; (4)

(b) Enumerate the disadvantages of an insulated neutral system; (4)

(d) Compare the use of an Earthed neutral system as opposed to the use of an Earthed neutral system with regard to the risk of electric shock from either system. (4)

Reference Answer

(a) Advantages of Insulated system:
The priority requirement on board ship is to maintain continuity of the electrical supply to essential equipments in the event of a single earth fault occurring. Because of supply is totally isolated from ship’s hull, there is no closed path, hence no current will flow to earth on occurring of single earth fault and equipments will continue to run. Short circuit will happen if double earthing happens in two different places in same phase.
Fault current is negligible in insulated system.
(b) Disadvantages of Insulated system:

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