Transmission of electricity

Question 1

Transmission of electricity

Answer 1

Bulky movement of electricity from generation sources to electrical substations

Question 2

Stages of electricity transmission

Answer 2

1. Generation
2. Step-up transformer
3. Transmission
4. Substations

Question 3

Components in transmission and distribution system

Answer 3

• National grid network
• Transformer stations
• Switch zones
• Main substation

Question 4

Role of transformer in electricity transmission

Answer 4

• Voltage Step-up
• Reducing Current
• Minimizing Power Loss.
• Efficient Transmission
• Voltage Step-down

Question 5

The switch zone

Answer 5

allows the electrical energy to be transmitted
through the National Grid Network

Question 6

The National Grid Network

Answer 6

: connects power stations at different
places together & transmits electrical power to various places throughout the country

Question 7

Main substation

Answer 7

Has transformers that step-down the voltage of electrical power to suitable value for distribution

Question 8

What does the transmission system provide

Answer 8

• Transmission at a very high voltage
• Carrying a three-phase supply on a smaller number of conductors

Question 9

Transmission at a very high voltage

Answer 9

• The voltage generated is stepped-up by a transformer at the power
  station
• The National Grid transmits +132 kV for long distance transmission
• By using high a voltage the power is carried by a smaller current & as
  power loss are proportional to
  I =current
  R=resistance
• Therefore the power loss is obviously much less if the current is small.
• At the consumer end, the voltage is stepped-down at a substation to 33kV & then down to 11kV & finally by another transformer to 240V which is the voltage for domestic use

Question 10

(2) Carrying a three-phase supply on a smaller
number of conductors

Answer 10

• Each phase has two wires from each generating coil, which are
  connected to the other two phases so that the three phases can be carried by four cables, one for each phase & a common neutral return cable

Question 11

Methods of connecting phases for transmission

Answer 11

• Star connection
• Delta connection

Question 12

Star connection

Answer 12

• In this configuration, one end of each phase winding is connected to a common point, creating a neutral point.

Question 13

Delta connection

Answer 13

• The voltage across each phase winding is equal to the line voltage.
• No neutral point

Question 14

Function of the isolator box

Answer 14

to isolate the x-ray unit
completely from the its supply