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Class 4 (4th Engineer) MET 📅 Mar 2026

Exam Question

(a) With reference to a three phase shipboard electrical distribution system, 

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

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

(b) Compare the use of an insulated neutral system as opposed to the use of an Earthed neutral system with regard to the risk of electric shock from either system. (8) 

Reference Answer

### (a) Advantages of an Insulated Neutral System (IT System)
An insulated neutral system, where the generator or transformer neutral is not connected to the ship's hull (earth), is the standard for low voltage ( 1000V) systems (often with resistance) and some specialized vessels or land-based systems. |
In summary, the **insulated neutral system is considered to provide a lower risk of electric shock for the crucial first-fault scenario** on board a ship. This, combined with the paramount need for continuity of essential services, is why it is the mandated and preferred system for low-voltage marine electrical distribution.
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