1) A 3-phase, 50 Hz overhead transmission line 100km. long has the following constants:
Resistance/km/phase = 0.1 ohm
Inductive reactance/km/phase = 0.2 ohm
Capacitive susceptance/km/ phase = 0.04 * 10-4 siemen
i) Sending end current
ii) Sending end voltage
iii) Sending end power factor and
iv) Transmission efficiency when supplying the balanced load of 10000 kW at 66 kV, p.f. 0.8 lagging.
2) Describe the voltage control of transmission line by:
i) Tap-changing transformers
ii) Synchronous condenser
iii) Induction regulators
3) A single core 66 kV cable working on 3-phase system has a conductor diameter of 2 cm. and a sheath of inside diameter 5.3 cm. If two intersheaths are introduced in such a way that the stress varies between the same maximum and minimum in the three layers, find:
a) Positions of intersheaths
b) Voltage on the intersheaths
c) Maximum and minimum stress
4) Derive an approximate expression for sag in overhead lines when supports are at the equal levels
5) a) describe what is lightning? describe the mechanism of lightning discharge.
b) describe the several kinds of the lightning stroke.
6) describe what is the surge absorber? Describe its types.