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The University of Sydney
Page 1 of 2
School of Electrical & Information Engineering
E
LEC
5204 POWER SYSTEMS ANALYSIS & PROTECTION
Tutorial 1
System Protection – Symmetrical Fault currents
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Question 1 (a)A generator has an impedance of 12% on a rating of 350MVA. Express this as impedance on 100MVA. (b)A 132 kV transmission line has an impedance of 50 ohms. Express this in % on 100MVA base? Per unit on 1000 MVA base? Question 2 A generator (which may be represented by an emf in series with and inductive reactance) is rated 500MVA, 22kV. Its Y-connected windings have a reactance of 1.1 per unit. (a)Find the ohmic value of the reactance of the windings (b)If the base values are specified as 100MVA, 20kV, find the per-unit value of the reactance of the windings Question 3 The three-phase fault level on a substation 66 kV busbar is 900 MVA. Determine, (a)The positive and negative sequence networks for a fault on this busbar. (b)The current in a 3-phase fault on the busbar. Question 4 A 33 KV line has a resistance of 5ohm and reactance of 20ohm respectively.

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