Q9. With reference to the protective devices fitted to a main alternating current generator, explain EACH of the following:
(a) overcurrent and short circuit protection; (2)
(b) generator negative phase sequence; (2)
(c) loss of field (excitation); (2)
(d) undervoltage; (2)
(e) reverse power. (2)
Q10. With reference to star delta starters used for three phase induction motors;
(a) explain in detail why this type of starter is employed. (4)
(b) explain, with the aid of a circuit diagram, the sequence of operation of a star delta starter. (6)
Q11. (a) Explain, with the aid of a sketch, the principle of operation of an earth leakage detection system of the instrument type (6)
(b) Explain why an insulated neutral system is used extensively on-board ships (2)
(c) State, with reasons, why a single earth fault on an insulated neutral system should always be cleared as soon as possible (2)
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