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Q8. With reference to shipboard three-phase electrical distribution systems:

(a) Describe the meaning of the term earth fault; (2)

(b) Explain the term protective earthing of electrical equipment, stating how it is achieved; (4)

(c) Sketch a clearly labelled circuit diagram of one arrangement for detecting phase to earth faults in an earthed neutral system; (5)

(d) Calculate the ohmic value of a neutral earthing resistor (NER) to limit the earth fault current to the full load rating of a 2 MW, 0.8 p.f., 3.3 kV generator. (5)