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Tampere University of Technology
Electrical Engineering

Fundamentals of Electrical and Power Engineering DEE-23106 — 16.10.2015
Anna Kulmala Programmable calculator allowed 5 guestions/ & 6 pts

Ouestion 1: — Fig 1 shows a special circuit where the diode D denotes an ideal diode. The initial values of
the circuit are zero. Compute the time-domain response of the voltage v., when a step
change of 1 A is applied to its input current. Utilize the basic relation between the capacitor
current and voltage for solving the problem. Sketch the waveform of Va

 

Fig. 1. The circuit of guestion 1.

Ouestion 2: — A three-phase load is fed through a three-phase feeder. The source phase voltage of phase a
at the feeding end of the feeder is 325cos(377t+55*)V. The feeder is 1.5 km long, having
parameters R = 1.3 O/km and X = 0.2 O/km. The load is a constant impedance load having
impedance of (10+j4)0/phase.

a) Draw the single-line diagram of the network and calculate the phase currents. Draw the
phasor diagram of the current and voltage of phase a.

b) Calculate the three-phase real power, reactive power, apparent power and power factor
of the source.

€) Calculate the three-phase real power, reactive power, apparent power and power factor
of the load.

Ouestion 3: — Fig. 2 presents an electric circuit and all the relevant parameter values are given on the
figure.
a) Determine the nodal admittance matrix of the electric circuit.
b) Calculate the voltage at node 2.
c) Determine the powers injected by the two voltage sources at nodes 1 and 3.

 

1 2 3
= f0- 0
JX=j0.2 p.u. JAX=j0.1 pu.
E=1.1 pv. JAX=j0.1 p.v. JX=j0.2 p.u. E=1 pv.

T jX=-j0.1 p.v.

Fig. 2. The electric circuit of guestion 3.

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Tampere University of Technology
Electrical Engineering

Fundamentals of Electrical and Power Engineering DEE-23106 — 16.10.2015
Anna Kulmala Programmable calculator allowed 5 guestions/ & 6 pts

Ouestion 4: — Draw the positive, negative and zero seguence impedance networks for the power system in
Fig. 3. Use per unit values.
Generator 1 (G1): 25 MVA, 11 kV, x” = 0.15, X2 = 0.1, X0=0.03 pu
Generator 2 (G2): 15 MVA, 11 kV, x” =0.2, X2=0.15, X0=0.05 pu
Synchronous motor 1 (M1): 25 MVA, 8 kV, X” =0.2, X2= 0.2, X0 = 0.1 pu
Transformer 1 (T1): 50 MVA, 11/220 kV, X=8%
Transformer 2 (T2): 25 MVA, 220/8 kV, X= 10%
Zero seguence reactance of the transmission line is 230 % of its positive seguence reactanee.

 
 

S

 

Fig. 3. The electric power system of guestion 4.

Ouestion 5: — Plana high-pass filter using any passive circuit components.
a) Draw the circuit diagram and determine the transfer function between output and input
voltages 4o/Uin-
b) Drawan approximate Bode diagram of your transfer function.
e) Determine such component values that the cutoff freguency of the filter is 350 Hz.

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