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Class 2 (2nd Engineer) MET 📅 Sep 2022

Exam Question

with reference to testing High Voltage equipment:

(a) Explain why earthing down is considered essential

(b) Briefly describe the procedures of earthing down

(c) Describe how an insulation resistance test is carried out on High Voltage equipment, making

reference to personnel safety

(d) Describe, with the aid of a sketch, a method to detect earth leakage in EACH of the following systems:

(i) Earthed

(ii) Insulated

Exam question diagramExam question diagram

Reference Answer

(d) (i) Earthed Neutral System:
In this system, the generator star point is connected directly to the ship’s hull.
Any earth leakage current will therefore complete a circuit back to the generator.
A Neutral Earthing Resistor (NER) is fitted to limit the earth fault current to about 5 Amps .

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