A single phase system is shown in the figure below.The transformers are rated as follows
T: 15 MVA, 13.8/138 kV, X = 10%
T2: 15 MVA, 138/69 kV,X = 8%
With the base in circuit Y chosen as 15 MVA, 138 kV, the impedance diagram in per unit is
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Solution
A 20 kV transmission line has a series impedance of(4 + j60) Ω and a shunt admittance of j0.5 S. Choose 100MVA and the line voltage as base values, the per-unit impedance and per-unit admittance of the line respectively are
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Solution
Effective inductance of the circuit across the terminals AB shown in the figure below is_____ H.
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Solution
Effective inductance across AB terminals
= L1+ L2+ L3–2M12– 2M13+ 2M23
= 4 + 5 + 6 – 2 (1) – 2 (3) +2 (2)
= 15 +4 –2 – 6 =11 H
Viewed from the terminals AB, following circuit shown in the figure can be reduced to an equivalent circuit at a single voltage source in series with a single resistor with following parameters.
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Solution
AC to DC circulating current dual converters are operated with which of the following relationship between their trigering angle (α1 and α2) ?
The polar plot at a type-1, 3-pole open loop system is shown in the figure. The closed loop system is
QUESTIONS CARRY TWO MARKS EACH.
A three-phase alternator generating unbalanced voltages is connected to an unbalanced load through a 3-phase transmission line as shown in figure. The neutral of the alternator and the star point of the load are slidly grounded. The phase voltages of the alternator are Ea =10∠0° V, Eb = 10∠0 – 90° V, Ec = 10∠120° V. The positive-sequence component of the load current is
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Solution
QUESTIONS CARRY TWO MARKS EACH.
A generator delivers power of 1.0 p.u. to an infinite bus through a purely reactive network. The maximum power that could be delivered by the generator is 2.0 p.u. A three-phase fault occurs at the terminals of the generator which reduces the generator output to zero. The fault is cleared after tc second. The original net work is then restored. The maximum swing of the rotor angle is found to be δmax= 110 electrical degree. Then the rotor angle in electrical degrees at t = tc is
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Solution
QUESTIONS CARRY TWO MARKS EACH.
A1 m A meter movement with an internal resistance of 100 Ω is to be converted in to a 0-100 mA ammeter. What is the value of required shunt resistance ?
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Solution
QUESTIONS CARRY TWO MARKS EACH.
Match the switch arrangements on the top row to the steady-state V-I characteristics on the lower row. The steady state operating points are shown by large black dots.
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Solution
Characteristics are as