Answer Happy

Q3. (total marks 20) a) In a power system protection scheme, make a distinction between a temporary fault and a 'permanent fault and how this may influence the behavior and design of the protection system. Include a brief explanation of the differences between, and the use of, 'disconnect switches', 'load break switches', and 'circuit breakers (5 Marks) b) High voltage circuit breakers, 11 kV and above, take five basic forms: Oil immersed or bulk oil Air blast Small oil volume Sulphur hexafluoride (SF6) Vacuum State one advantage and one disadvantage of each of the five circuit breaker types (10 Marks) c) System protection typically involves several different types of protective relays and a number of 'zones' - geographic parts of the system. i. Discuss how impedance relays can be used in a relay coordination scheme. ii. (2 Marks) State the type(s) of relay often used to protect the following equipment: Transformers, busbars, and generators Transmission lines Distribution lines which typically are radial in nature