The ratings of a three-phase three-winding transformer are Primary(1): Y connected 66 kV, 15 MVA Secondary (2): Y connected, 13 . 2 kV , 1 0 MVA Tertiary (3): A connected, 2.3 kV , 5 MVA Neglecting winding resistances and exciting current, the per-unit leakage reactances are X 12 = 0.08 on a 15-MVA, 66-kV base X 13 = 0.10 on a 15-MVA, 66-kV base X 23 = 0.09 on a 10-MVA, 13 .2-kV base (a) Determine the per-unit reactances X 1 , X 2 , X 3 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.
The ratings of a three-phase three-winding transformer are Primary(1): Y connected 66 kV, 15 MVA Secondary (2): Y connected, 13 . 2 kV , 1 0 MVA Tertiary (3): A connected, 2.3 kV , 5 MVA Neglecting winding resistances and exciting current, the per-unit leakage reactances are X 12 = 0.08 on a 15-MVA, 66-kV base X 13 = 0.10 on a 15-MVA, 66-kV base X 23 = 0.09 on a 10-MVA, 13 .2-kV base (a) Determine the per-unit reactances X 1 , X 2 , X 3 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.
Solution Summary: The author calculates the three-phase transformer without winding resistances and excitation current as an ideal transformer.
The ratings of a three-phase three-winding transformer are
Primary(1): Y connected
66
kV,
15
MVA
Secondary (2): Y connected,
13
.
2 kV
,
1
0
MVA
Tertiary (3): A connected,
2.3
kV
,
5
MVA
Neglecting winding resistances and exciting current, the per-unit leakage reactances are
X
12
=
0.08
on a
15-MVA,
66-kV
base
X
13
=
0.10
on a
15-MVA,
66-kV
base
X
23
=
0.09
on a
10-MVA,
13
.2-kV
base
(a) Determine the per-unit reactances
X
1
,
X
2
,
X
3
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 the single-phase, three-
winding, transformer, the
primary current is equal to lo at
the condition of
ints
there is no load on tertiary windings
the current in secondary windings equal
to zero
the resistances (R1, R2, and R3) in
transformer windings are equal
the inductances (L1, L2, and L3) in
transformer windings are equal.
The ratings of a single-phase three-winding transformer are as follows:*primary winding: 300 MVA, 14kV*secondary winding: 300MVA, 200kV*tertiary winding: 40MVA, 20kV.
The leakage reactances are:*Xps = 0.1 at 300MVA, 14kV*Xpt = 0.16 at 40MVA, 14kV*Xst = 0.14 at 50MVA, 200kV
Neglecting the winding resistance and exciting current, calculate Xp, Xs and Xt using 300 MVA and 14kV as the base for the primary winding.
In no load phasor diagram of practical
transformer, the magnetizing current is
with flux 4.
In phase
90 Degree out of phase
Lagging by 60 Degrees
Leading by 60 Degrees
Chapter 3 Solutions
Power System Analysis and Design (MindTap Course List)
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