Electrical Power Systems 6th. Edition by C. L. WADHWA | 9781906574031 | 1906574030 | Holooly

Electrical Power Systems

131 SOLVED PROBLEMS

Question: 21.1

A load of 30 MW, 45 MVAR is connected to a line where X to R ratio is 5 and the short circuit capacity of the load bus is 250 MVA. The supply voltage is 11 kV and the load is star connected. Determine the load bus voltage. ...

Verified Answer:

The load per phase is (10+j 15) MVA and SCC. [late...

Question: C.3

A synchronous motor is connected to an infinite bus and draws 1.0 p.u. current at 1.0 p.u. Voltage (i) 0.9 p.f. lag and (ii) 0.9 p.f. lead. The synchronous reactance of the motor is 1.0 p.u. (a) Determine E, Q, I, δ, P (b) If the excitation is increased by 10%, determine E, Q, I, δ P, cos Φ (c) If ...

Verified Answer:

(a) (i) p.f. 0.9 lag E = V – j I

X_{d}[/lat...

Question: C.2

An alternator is connected to an infinite bus bar and delivers 1.0 p.u. current at 1.0 p.u. voltage and p.f. (i) 0.95 lag (ii) 0.95 lead. The reactance of the alternator Xd = 1.0 p.u. Determine (a) P, Q, E and δ (b) If the excitation is reduced by 20%, calculate P, Q, E, δ, cos Φ1 and current I. ...

Verified Answer:

(i) 0.95 lag E = 1.0 + j 1.0 (0.95 – j 0.3122) = 1...

Question: C.1

An alternator delivers 1.0 p.u. current at 1.0 p.u. voltage and p.f. (i) 0.8 lag (ii) 0.8 lead to an infinite bus. The reactance of the alternator Xd is 1.0 p.u., Determine (a) P, Q, E and δ (b) If the excitation is increased by 20%, calculate P, Q, E, δ, cos Φ and I. (c) If the system is as in (a) ...

Verified Answer:

(i) Given

\quad V=1 \angle 0^{\circ}, \cos ...

Question: A.3

Develop Zbus matrix for the network shown in Fig. E. A.3. ...

Verified Answer:

Z_{\text {bus }}

for the element 1-...

Question: A.2

A network consists of three elements 0-1, 1-2 and 2-0 of p.u. impedances 0.2, 0.4 and 0.4 respectively. Determine the bus impedance matrix. ...

Verified Answer:

For element 0-1

Z_{\text {bus }}=[0.2][/lat...

Question: A.1

Consider the network shown in the following Fig. E. A.1. The bus numbers and impedances are marked. Determine the bus impedance matrix. ...

Verified Answer:

Taking one element at a time, say we take node 1 c...

Question: 9.1

Determine the economic overall diameter of a 1-core cable metal sheathed for a working voltage of 85 kV if the dielectric strength of the insulating material is 65 kV/cm. ...

Verified Answer:

For economic size the ratio of the outer dia to th...

Question: 8.3

A string of eight suspension insulators is to be fitted with a grading ring. If the pin to earth capacitances are all equal to C, find the values of line to pin capacitances that would give a uniform voltage distribution over the string. ...

Verified Answer:

For voltage distribution to be uniform (see Fig. E...

Question: 8.1

Determine the maximum voltage that the string of the suspension insulators in Fig. E.8.1 can withstand if the maximum voltage per unit is 17.5 kV. ...

Verified Answer:

Let the voltages across the various units be [late...

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