Question

A Wye-Delta transformer is connected to a 66 kV input three-phase transmission line. Each transformer is rated at 1000 kVA and has a step-down ratio of 8:1. The bank supplies a balance load having a power factor of 0.8 lag with a load current of 70 A. Assume ideal transformer, determine.

- The primary line and phase voltages
- The secondary line and phase voltages
- The secondary line and phase currents
- The apparent and active power at the load
- Total kVA capacity of the transformer

Answer #1

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A three-phase wye-connected (Y) synchronous generator is
operating at Ea = 8.OLO° kV (lineneutral) and has synchronous
reactance of X~ = 1.0 fl . The generator is connected to a
threephase delta-wye connected step-down transformer that is
constructed from three individual single-phase transformers. Each
the single-phase transformers has rated power of 200 kVA has a
turns ratio of 4:1 where the rated primary voltage of 8.0 kV and a
rated secondary of 2.0 kV and a per-unit series reactance of...

Plate values of a three-phase transformer are given
below:
1600 kVA, 15 kV / 400 V, 50 Hz, io = 1.2%; ukN = 6%, idle losses
2450 W, rated
copper losses of power 14500 W; Dy5.
a) Calculate primary and secondary line and phase currents.
b) Secondary at 75% load in power factor with 0.85 inductance and
0.85 capacity
calculate the voltage separately. Compare and interpret the
results. capacity
at what time of day can the upload be seen? To...

Plate values of a three-phase transformer are given
below:
1600 kVA, 15 kV / 400 V, 50 Hz, io = 1.2%; ukN = 6%, idle losses
2450 W, rated
copper losses of power 14500 W; Dy5.
a) Calculate primary and secondary line and phase currents.
b) Secondary at 75% load in power factor with 0.85 inductance and
0.85 capacity
calculate the voltage separately. Compare and interpret the
results. capacity
at what time of day can the upload be seen? To...

A 100 MVA, 13.2 kV three phase generator (G) having a
synchronous reactance of 10% is connected to a three phase Y-Y
transformer T1 which feeds a 132 kV 10 miles transmission line
having an impedance per phase of 2 + j5 ?/mile. At the receiving
end of the transmission line is a Y-Y step down transformer T2.
Three loads are connected to the secondary side of the transformer
T2. Loads are as follows:
Load#1 40 MVA at 0.8 pf...

Plate values of a three-phase transformer are given below:
1600 kVA, 15 kV / 0,4 kV, 50 Hz, i0 = 1.2%;
ukN= 6%, idle losses 2450 W, rated power copper losses
14500 W; Dy5 connected..
III) There is 75% load in the power factor with 0.85 inductance
and 0.85 capacity. At what times of the day can capacity loading be
seen? What solution should be applied to prevent voltage
change?
IV) Draw the fastening group. How can this transformer be...

A single phase transformer rated at
3000 KVA, 69kV, 60 Hz has a total internal impedance Zp of 127ohm,
referred to the primary side.
Calculate:
a) primary and secondary
currents
b) voltage regulation from no load to
full load for 2000 kW resistive load, knowing that the primary
voltage supply is fixed at 69 kV.
c) primary and secondary currents if
the secondary is accidentally short circuited.

Three single phase transformers having a 15:1 ratio are
wye-connected to a 2400 V three phase line as a step-down
transformer. What is the line voltage of each transformer? What is
the secondary voltage of each transformer if they are delta
connected to the same line?

The transformer is protected by a differential relay. The relay
is connected to three phase transformer, 50 MVA, 22 kV/33 kV delta
– star connection. The relay is connected in delta. The current
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at the high voltage. Calculate the primary and secondary current of
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A 1200 kVA, 2.3 kV, 3-phase, star - connected alternator has a
resistance of 0.401 /phase and a synchronous reactance of 3.21
/phase. If the generator is supplying a load at a power factor of
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at the output terminals of the generator if the load is suddenly
disconnected. Assume the speed and the excitation current is to
remain unchanged.

The line current of a three-phase engine in delta configuration
is 25 A, connected to a supply network with a line voltage of 240 V
and absorbing a power of 15 kW. The efficiency of the engine is
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Taking as a reference of line voltages V1= V∠0º, and a direct
sequence, find:
a) The phasors of the line voltages
b) The phasors of the line and phase currents
c) The reactive and apparent power
d) The mechanical power (at...

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