Power Distribution and Earthing Systems

What is the initial voltage of electricity generated at power stations before it is stepped up for transmission?

• 132,000 volts AC

• 25,000 volts AC

• 400 volts AC

• 11,000 volts AC

To what higher voltage is electricity stepped up for transmission on the National Grid network?

• 400,000 volts AC

• 11,000 volts AC

• 230 volts AC

• 400 volts AC

Why is electricity transmitted at high voltages?

• To increase the current

• To increase voltage drop

• To reduce the conductor size and cost

• To increase the weight of conductors

What is the voltage level when electricity is transformed down at local substations for domestic use?

• 230 volts AC

• 11,000 volts AC

• 132,000 volts AC

• 400,000 volts AC

What does TNS stand for in UK domestic electrical installations?

• Terra Neutral Separate

• Terra Neutral System

• Terra Neutral Single

• Terra Neutral Secure

What is the maximum earth fault loop impedance for a TNS system?

• 1 ohm

• 200 ohms

• 0.8 ohms

• 0.35 ohms

What does TT system rely on for earth protection?

• The physical earth

• The outer sheathing of the supply cable

• A separate earth conductor

• A combined earth and neutral conductor

What is the maximum earth fault loop impedance for a TNCS system?

• 1 ohm

• 200 ohms

• 0.8 ohms

• 0.35 ohms

What additional protection is always provided in a TT system?

• Circuit breaker

• RCD protection

• Fuse protection

• Surge protector

Which of the following is NOT a property of the supply authority?

• The meter

• The fuse

• The consumer unit

• The supply cable