A 100,000-kVA 230/115-kV ∆-∆ three-phase power transformer has a per-unit resistance of 0.02 pu and a per-unit reactance of 0.055 pu. The excitation branch elements are RC = 110 pu and X M = 20 pu . a) If this transformer supplies a load of 80 MVA at 0.85 PF lagging, draw the phasor diagram of onephase of the transformer. (b) What is the voltage regulation of the transformer bank under these conditions? (c) Sketch the equivalent circuit referred to the low-voltage side of one phase of this transformer. Calculate all of the transformer impedances referred to the low-voltage side

A 100,000-kVA 230/115-kV ∆-∆ three-phase power transformer has a per-unit resistance of 0.02 pu and a per-unit reactance of 0.055 pu. The excitation branch elements are RC = 110 pu and X M = 20 pu . a) If this transformer supplies a load of 80 MVA at 0.85 PF lagging, draw the phasor diagram of onephase of the transformer. (b) What is the voltage regulation of the transformer bank under these conditions? (c) Sketch the equivalent circuit referred to the low-voltage side of one phase of this transformer. Calculate all of the transformer impedances referred to the low-voltage side

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 3.16P: A single-phase, 50-kVA,2400/240-V,60-Hz distribution transformer has the following parameters:...

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Consider Figure 3.25 of the text for a transformer with off-nominal turns ratio. (i) The per-unit equivalent circuit shown in part (c) contains an ideal transformer which cannot be accommodated by some computer programs. (a) True (b) False (ii) In the - circuit representation for real c in part (d), the admittance parameters Y11 and Y12 would be unequal. (a) True (b) False (iii) For complex c, can the admittance parameters be synthesized with a passive RLC circuit? (a) Yes (b) No
The transformer of Problem 3.16 is supplying a rated load of 50 kVA at a rated secondary voltage of 240 V and at 0.8 posr factor lagging. Neglect the transformer exciting current. (a) Determine the input terminal voltage of the transformer on the high-voltage side. (b) Sketch the corresponding phasor diagram. (c) If the transformer is used as a step-down transformer at the load end of a feeder whose impedance is 0.5+j2.0, find the voltage VS and the power factor at the sending end of the feeder.
A single-phase 100-kVA,2400/240-volt,60-Hz distribution transformer is used as a step-down transformer. The load, which is connected to the 240-volt secondary winding, absorbs 60 kVA at 0.8 power factor lagging and is at 230 volts. Assuming an ideal transformer, calculate the following: (a) primary voltage, (b) load impedance, (c) load impedance referred to the primary, and (d) the real and reactive power supplied to the primary winding.
An infinite bus, which is a constant voltage source, is connected to the primary of the three-winding transformer of Problem 3.53. A 7.5-MVA,13.2-kV synchronous motor with a sub transient reactance of 0.2 per unit is connected to the transformer secondary. A5-MW,2.3-kV three-phase resistive load is connected to the tertiary Choosing a base of 66 kV and 15 MVA in the primary, draw the impedance diagram of the system showing per-unit impedances. Neglect transformer exciting current, phase shifts, and all resistances except the resistive load.
Consider a source of voltage v(t)=102sin(2t)V, with an internal resistance of 1800. A transformer that can be considered as ideal is used to couple a 50 resistive load to the source. (a) Determine the transformer primary-to-secondary turns ratio required to ensure maxi mum power transfer by matching the load and source resistances. (b) Find the average power delivered to the load, assenting maximum power transfer.
Consider Figure 3.4. For an ideal phase-shifting transformer, the imda nce is unchanged when it is referred from one side to the other. (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 ?
An ideal transformer has no real or reactive power loss. (a) True (b) False
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Given a transformer (single-phase, 10kVA, 2400/240V, 60Hz) Z1 = 5.2 + j12.5 ohms; Z2 = 0.06 + j0.12 ohm. When operating at rated primary voltage and frequency, the transformer delivers rated current to its load at 0.8 pf LAGGING. Solve for the load voltage in VOLTS - (Neglecting the no-load current.)
Primary side-reduced equivalent circuit parameters of a 25 KVA, 50 Hz, 4000/400 Volt transformer R1 = 32 Ω, X1 = 45 Ω, Rc = 250000 Ω, R2 '= 66.14 Ω, X2' = 79.34 Ω, Xm It is given as = 30000 Ω. Since the secondary of the transformer is fed at a full load rated voltage with an advanced power factor of 0.9, for these operating conditions; a) Calculate the primary voltage using the T equivalent circuit. (Only the amplitude of the voltage and the phase value will not be entered.) b) Calculate the efficiency of the transformer. c )Calculate the voltage regulation of the transformer.
A 2000/400 V, 100 kVA, 60 Hz step-down single-phase transformer has a primary and secondary resistances of 0.2ohm and 0.05 ohm respectively, the corresponding leakage reactances being 0.3 ohm and 0.01 ohm respectively.1. Calculate the equivalent resistance, reactance and impedance referred to the low-voltage (secondary) side.2. Find the high (primary) voltage when the transformer is supplying full-load current at rated secondary voltage at 0.8 powerfactor lagging.3. Draw the phasor diagram showing your answer in 2.