# XFMR_exc - transfer an impedance from one side to the other...

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Due Wed Sep 23rd - 5:00 PM Please use homework cover sheet. This is an INDIVIDUAL homework set.

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4) [10 pts] Answer both of the following short essay questions. a) [5 pts] A coworker questions the calculations you performed when converting Z 12 , Z 13 and Z 23 to Z 1 , Z 2 and Z 3 for a 3-winding transformer. He says that since Z 2 is negative, you've made a mistake. What do you tell him (be polite)? b) [5 pts] A conceptual phase-shifting transformer is used in positive and negative sequence networks to represent the phase shift of the phase A voltages and currents from one side to the other. Ratios like 1/30 E or 1/-30 E are common. What effect do these phase shifting transformers have if you want to

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Unformatted text preview: transfer an impedance from one side to the other? 5) [15 pts] A new 3 φ transformer has the following self-cooled (OA or ONAN) ratings: Primary: Y-connected, 345 kV, 296 MVA Secondary: Y-connected, 118 kV, 296 MVA Tertiary: Δ-connected, 13.8 kV, 77 MVA Binary short-circuit tests performed at the factory give the following results: Z 12 = 6.21% on 296-MVA 345-kV base. Z 13 = 55.9% on 77-MVA 118-kV base. Z 23 = 42.1% on 77-MVA 13.8-kV base. Find the per unit impedances Z 1 , Z 2 and Z 3 on a base of 100 MVA, 138 kV. These must be provided to your systems studies engineers. It may be helpful to refer to section 2.8 of your text book....
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XFMR_exc - transfer an impedance from one side to the other...

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