Tutorial 1.7The three-phase ratings of a three-winding transformer are:Primary Y-connected, 66 kV, 24 MVAY-connected, 13.2 kV, 12 MVASecondaryTertiaryA-connected, 2.3 kV, 4 MVANeglecting resistance, the leakage impedances are:ZpsZns = 6% on 24 MVA, 66 kV baseZpt = 8% on 24 MVA, 66 kV baseZst = 7% on 12 MVA, 13.2 kV baseFind the per-unit impedances of the per-phase equivalent circuit for a base of 24 MVA, 66 kV inthe primary circuit.{Ans: j 0.0; j 0.06; j 0.08}

Answered: Image /qna-images/answer/3b8e9e0d-4c1f-4403-848a-f1c48b8d901a.jpg

The three-phase ratings of a three-winding transformer are: Primary Y-connected, 66 kV, 24 MVA Y-connected, 13.2 kV, 12 MVA Secondary Tertiary A-connected, 2.3 kV, 4 MVA Neglecting resistance, the leakage impedances are: Zps = 6% on 24 MVA, 66 kV base Znt 8% on 24 MVA, 66 kV base "pt = Zst = 7% on 12 MVA, 13.2 kV base Find the per-unit impedances of the per-phase equivalent circuit for a base of 24 MVA, 66 kV in the primary circuit. {Ans: j 0.0; j 0.06; j 0.08}

The three-phase ratings of a three-winding transformer are: Primary Y-connected, 66 kV, 24 MVA Y-connected, 13.2 kV, 12 MVA Secondary Tertiary A-connected, 2.3 kV, 4 MVA Neglecting resistance, the leakage impedances are: Zps = 6% on 24 MVA, 66 kV base Znt 8% on 24 MVA, 66 kV base "pt = Zst = 7% on 12 MVA, 13.2 kV base Find the per-unit impedances of the per-phase equivalent circuit for a base of 24 MVA, 66 kV in the primary circuit. {Ans: j 0.0; j 0.06; j 0.08}

Power System Analysis and Design (MindTap Course List)

6th Edition

ISBN:9781305632134

Author:J. Duncan Glover, Thomas Overbye, Mulukutla S. Sarma

Publisher:J. Duncan Glover, Thomas Overbye, Mulukutla S. Sarma

Chapter3: Power Transformers

Section: Chapter Questions

Problem 3.53P: The ratings of a three-phase, three-winding transformer are Primary: Y connected, 66kV,15MVA...

See similar textbooks

Similar questions

The ratings of a three-phase three-winding transformer are Primary(1): Y connected 66kV,15MVA Secondary (2): Y connected, 13.2kV,10MVA Tertiary (3): A connected, 2.3kV,5MVA Neglecting winding resistances and exciting current, the per-unit leakage reactances are X12=0.08 on a 15-MVA,66-kV base X13=0.10 on a 15-MVA,66-kV base X23=0.09 on a 10-MVA,13.2-kV base (a) Determine the per-unit reactances X1,X2,X3 of the equivalent circuit on a 15-MVA,66-kV base at the primary terminals. (b) Purely resistive loads of 7.5 MW at 13.2 kV and 5 MW at 2.3kV are connected to the secondary and tertiary sides of the transformer, respectively. Draw the per- unit impedance diagram, showing the per-unit impedances on a 15-MVA,66-kV base at the primary terminals.
In per-unit equivalent circuits of practical three-phase transformers, under balanced thr-phase operation, in which of the following connect ions would a phase-shifting transformer come up? (a) Y-Y (b) Y- (c) -
A single-phase, 50-kVA,2400/240-V,60-Hz distribution transformer has the following parameters: Resistance of the 2400-V winding: R1=0.75 Resistance of the 240-V winding: R2=0.0075 Leakage reactance of the 2400-V winding: X1=1.0 Leakage reactance of the 240-V winding: X2=0.01 Exciting admittance on the 240-V side =0.003j0.02S (a) Draw the equivalent circuit referred to the high-voltage side of the transformer. (b) Draw the equivalent circuit referred to the low-voltage side of the transformer. Show the numerical values of impedances on the equivalent circuits.
For a short-circuit test on a 2-winding transformer, with one winding shorted, can you apply the rated voltage on the other winding? (a) Yes (b) No
For an ideal 2-winding transformer, an impedance Z2 connected across winding 2 (secondary) is referred to winding 1 (primary) by multiplying Z2 by (a) The turns ratio (N1/N2) (b) The square of the turns ratio (N1/N2)2 (c) The cubed turns ratio (N1/N2)3
In order to avoid difficulties with third-harmonic exciting current, which three-phase transformer connection is seldom used for step-up transformers between a generator and a transmission line in power systems. (a) Y- (b) -Y (c) Y-Y
Three single-phase, two-winding transformers, each rated 450MVA,20kV/288.7kV, with leakage reactance Xeq=0.10perunit, are connected to form a three-phase bank. The high-voltage windings are connected in Y with a solidly grounded neutral. Draw the per-unit equivalent circuit if the low-voltage windings are connected (a) in with American standard phase shift or (b) in Y with an open neutral. Use the transformer ratings as base quantities. Winding resistances and exciting current are neglected.
An ideal transformer has no real or reactive power loss. (a) True (b) False
A bank of three single-phase transformers, each rated 30MVA,38.1/3.81kV, are connected in Y- with a balanced load of three 1, Y-connected resistors. Choosing a base of 90MVA,66kV for the high-voltage side of the three-phase transformer. spify the base for the low-voltage side. Compute the per-unit resistance of the load on the base for the low-voltage side. Also, determine the load resistance in ohms referred to the high-voltage side and the per-unit value on the chosen base.
The ratings of a three-phase, three-winding transformer are Primary: Y connected, 66kV,15MVA Secondary: Y connected, 13.2kV,10MVA Tertiary: connected, 2.3kV,5MVA Neglecting resistances and exciting current, the leakage reactances are: XPS=0.09 per unit on a 15-MVA,66-kV base XPT=0.08 per unit on a 15-MVA,66-kV base XST=0.05 per unit on a 10-MVA,13.2-kV base Determine the per-unit reactances of the per-phase equivalent circuit using a base of 15 MVA and 66 kV for the primary.
The ideal transformer windings are eliminated from the per-unit equivalent circuit of a transformer. (a) True (b) False
(a) An ideal single-phase two-winding transformer with turns ratio at=N1/N2 is connected with a series impedance Z2 across winding 2. If one wants to replace Z2, with a series impedance Z1 across winding 1 and keep the terminal behavior of the two circuits to be identical, find Z1 in terms of Z2. (b) Would the above result be true if instead of a series impedance there is a shunt impedance? (c) Can one refer a ladder network on the secondary (2) side to the primary (1) side simply by multiplying every impedance byat2 ?