Unit 7: Power System Components

Question 1

What are electrical power systems?

Answer 1

System that generates & delivers power to the load.
Have high reliability & efficiency.

Question 2

Basic Structure of Power Systems

Answer 2

1 = Generation
2 = Transmission
3 = Distribution
4 = Load

Question 3

What is the phase voltage of the UK grid?

Answer 3

230 V

Question 4

What is the line voltage of the UK grid?

Answer 4

400 V

Question 5

What is the frequency of the UK grid?

Answer 5

50 Hz

Question 6

What is the frequency of stand alone systems e.g aircraft?

Answer 6

400 Hz

Some new aircraft like 787 designed to 800 Hz

Question 7

Key Component of a Power System [6]

Answer 7

• Power Generators
• Transformers
• Transmission Lines
• Substations
• Capacitors
• Loads

Question 8

How is power generated in a power system (generally)?

Answer 8

Most maintained by electromechanical conversion using synchronous machines.
Output at 5-30kV (higher = more insulation)

Question 9

What do OCGT and CCGT stand for?

Answer 9

OCGT = Open Cycle Gas Turbine
CCGT = Closed Cycle Gas Turbine

Question 10

What are the main types of transformers and their uses? [5]

Answer 10

Substation = step up/down
Distribution = near load centres to reduce V
Service = reduce to household level
Potential = measure high Voltages
Current = measure high Currents

Question 11

What is the purpose of transmission lines?

Answer 11

High voltage wires on tall towers used to move electricity around (220 - 1200kV)
Most made of aluminium as cheaper & lighter than copper.

Question 12

Insulators & Their Design

Answer 12

Consist of multiple conical shaped disks around a rod that insulates it.
Conical increases flashover distance & automatically clear off rain.

Question 13

Methods of protection within electrical power systems

Answer 13

• Circuit Breakers
• Disconnect Switch
• Surge Arrester

Question 14

Circuit Breakers

Answer 14

3 pole switch at each end of transmission line sections.
Open in event of fault or short circuit.

Question 15

Disconnect Switch

Answer 15

In series with CB’s to isolate them when open.
Can also be used to sectionalise + isolate sections of a network.

Question 16

Surge Arrester

Answer 16

Protect vulnerable equipment from surges e.g transformers, substations etc.

Question 17

What is an Energy Control Centre?

Answer 17

Monitors & Controls power systems by performing Power Dispatching, Security Control & Supervisory Control