Reflection & Refraction of Waves of Travelling Waves

Q. A surge of $20kV$ magnitude travels along a lossless cable towards its junction with two identical lossless overhead transmission line. The inductance and the capacitance of the cable are $0.4mH$ and $0.5\mu F$ per km. The magnitude of the voltage at the junction due to surge is

1. 36.72 kV
2. 18.36 kV
3. 6.07 kV
4. 33.93 kV

Q.

The RMS voltage shown in the waveform is

Q. Total instantaneous power supplied by 3-phase ac supply to a balanced R-L load is

1. zero
2. constant
3. pulsating with zero average
4. pulsating with non-zero average

Q. A 100 kV, 2 micro sec rectangular surge on a line having a surge impedance of 300 $\Omega$ approaches a station at which concentrated earth capacitance is 3000 pF. The maximum value of transmitted value is___kV.

1. 178.32

Q. The reflection coefficient for the transmission line shown in the figure at $\rho$ is

1. +1
2. -1
3. 0
4. 0.5

Q. An overhead line 300 km long and having surge inpedance loading of $100\Omega$. The line is open circuited at the receiving end and voltage of 500V is applied to the other end. Calculate the sending end voltage and current after 0.002 sec

1. 500 V, -5A
2. 1000 V, +5A
3. 500 V, +5A
4. 500 V, -10A

Q.

Given that V${}_{s1}$ = V${}_{s2}$ = 1 + j0 p.u. +ve sequence impendance are Z${}_{s1}$ = Z${}_{s2}$ = 0.001 + j0.01 p.u and Z${}_L$ = 0.006 + j0.06 p.u, 3-$\varphi$. Base MVA = 100, voltage base = 400 kV(L-L).

Nominal system frequency = 50 Hz. The reference voltage for phase 'a' is deifned as V(t) = V${}_m$ cos($\omega$t). The symmetrical 3$\varphi$ fault occurs at centre of the line i.e, at point 'F'. At the time '$t_0$' the +ve sequence impendance from source S${}_1$ to point 'F' equals (0.004 + j0.04) p.u. The wave form corresponding to phase 'a' fault current from bus X reveals that decaying d.c. offset current is -ve in magnitude at its maximum initial value. Assuming that the negative sequence impedances are equal to +ve sequence impendances and the zero sequence (Z) are 3 times of +ve sequence (Z).

The instant (t${}_0$) of the fault will be

1. 4.682 ms
2. 9.667 ms
3. 14.667 ms
4. 19.667 ms

Q. Consider a step voltage wave of magnitude 1 pu travelling along a lossless transmission line that terminates in a capacitor. The voltage magnitude across the capacitor at the instant travelling wave reaches the capacitor is

1. 0
2. +1
3. -1
4. +2