1
GATE EE 2001
Subjective
+5
-0
A 132 kV transmission line AB is connected to a cable BC. The characteristic impedances of the overhead line and the cable are 400$$\Omega$$ and 80$$\Omega$$ respectively. Assume that these are purely resistive. A 250 kV switching surge travels from A to B.

(a) Calculate the value of this voltage surge when it first reaches C.

(b) Calculate the value of the reflected component of this surge when the first reflection reaches A.

(c) Calculate the surge current in the cable BC.

2
GATE EE 2000
Subjective
+5
-0
A $$275$$ $$kV,$$ $$3$$-phase, $$50$$ $$Hz,$$ $$400$$ $$km$$ lossless line has following parameters:
$$x=0.05$$ $$ohms/km,$$ line charging susceptance $$y=3.0$$ micro-Siemens/k.

(a) Calculate the receiving end voltage on open circuit using justifiable assumptions.

(b) What load at the receiving end will result in a flat voltage profile on the line?

(c) If the flat voltage profile is to be achieved at $$1.2$$ times the loading in (b), what will be the nature and quantum of uniformly distributed compensation required?

3
GATE EE 1999
Subjective
+5
-0
A 66 kV, 3-phase, 50 Hz, 150 km long overhead transmission line is open circuited at the receiving end. Each conductor has a resistance of 0.25$$\Omega$$/km, an inductive reactance of 0.5$$\Omega$$/km and a capacitive admittance to neutral of 0.04 $$\times$$ 10-4 S/km.

(a) Draw the nominal π-equivalent circuit and indicate the value of each parameter.
(b) Calculate the receiving end voltage if the sending end voltage is 66 kV.

4
GATE EE 1999
Subjective
+5
-0
A 6.6 kV, 50 Hz single core lead sheathed cable has the following data:
Conductor diameter: 1.5 cm, length: 4 km. Internal diameter of the sheath : 3 cm
Resistivity of insulation : 1.3 $$\times$$ 1012 $$\Omega$$-m. Relative permittivity of insulation : 3.5 Calculate

(a) the insulation resistance
(b) the capacitance and
(c) the maximum electric stress in the insulation

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