Overcurrent Protection

What does Zs represent in an electrical circuit?

• Device rating

• Cable length

• Earth fault loop impedance

• Maximum current rating

What is the standard disconnection time for a final circuit up to 32A on a TN system?

• 1 second

• 0.4 seconds

• 5 seconds

• 2 seconds

Which device provides overcurrent protection?

• RCD

• RCBO

• MCB

• Both b and c

What does Ib represent?

• Design current

• Device rating

• Cable rating

• Voltage drop

What is the maximum Zs for a 32A Type C MCB (100% value)?

• 1.44 ohms

• 0.72 ohms

• 0.44 ohms

• 5.0 ohms

What is the volt drop limit for power circuits?

• 3%

• 5%

• 10%

• 7%

What is the maximum Zs for a 30mA RCD?

• 50 ohms

• 1.67 ohms

• 1667 ohms

• 3 ohms

Overcurrent is defined as a situation where the current exceeds the rated value. What are the types of overcurrent?

• Short-circuit current and earth fault current

• Overload current and short-circuit current

• Earth fault current and overload current

• Short-circuit current and transient current

Automatic Disconnection of Supply (ADS) is a safety mechanism used in electrical systems to:

• prevent overload by disconnecting supply automatically

• ensure continuous power supply

• reduce electricity bills

• increase power output

List three factors affecting cable selection.

• Material, Length, Voltage

• Color, Brand, Price

• Weight, Flexibility, Conductivity

• Insulation, Temperature, CSA