Page 317 - Electrician - TT (Volume 2)

ELECTRICIAN - CITS

These substations also contain circuit breaker, fuses and lightning arrestors to protect expensive apparatus and
provide quick isolation of faulted lines from the system.
Types power lines
a Low tension - operating at 1000V or less

b High tension - voltage is up to 11 KV.
c Super tension - 22Kv to 33 KV
d Extra high tension - 33 to 66 KV
e Extra super voltage conductor - beyond 132 KV
Advantages of high voltage transmission

1 It reduces volume of conductor material
2 Increases transmission efficiency
3 Decreases percentage line drops
Disadvantages of high voltage transmission
1 Increased cost of insulating the conductor

2 Because of increased cost of transformer switch gears are used.
Advantages of high voltage DC transmission
1 It requires only two conductors
2 No inductance, capacitance and phase difference.

3 No skin effect.
4 Insulation stress is less
5 Less corona loss
6 Dielectric loss is less suitable for cable
7 No stability problems and synchronizing difficulties

8 DC transmission line has better voltage regulation
9 Advantages of high voltage DC transmission
Disadvantages of high voltage DC transmission
1 Electric power cannot be generated at high DC voltage
2 DC cannot be stepped up

3 Dc switches and circuit breakers have their own limitations
Advantages of high voltage AC transmission
1 Power can be generated at high voltage.
2 Maintenance of AC stations is easy and cheaper.
3 It can be stepped up or stepped down by transformer with ease and efficiency

Disadvantages of high voltage AC transmission
1 Require more copper or conductor
2 AC transmission line is more complicated
3 Skin effect

4 Has capacitance and there for continuous loss of power due to charging

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CITS : Power - Electrician & Wireman - Lesson 106-116