What are 3 statements about function switching

• May be used for operational control

• Functional switching devices are intended for secure isolation of circuits during maintenance work.

• Control several items of equipment

• Must be derated controlling a load with a low pf

What is the main purpose of using SELV® or PELV® systems to reduce electrical hazards

• They ensure that circuits are protected by automatic disconnection of the supply if a fault occurs.

• Provide basic and fault protection, reduced voltage levels

• They allow circuits to be directly connected to earth, improving overall safety.

• 4

  They provide fault protection through grounding of the neutral conductor.

What is a true statement of SELV/PELV arrangements?

• SELV/PELV systems can share the same enclosure with high-voltage circuits as long as they are properly fused.

• SELV and PELV circuits can be interconnected with higher voltage systems as long as the voltage is under 60V.

• SELV/PELV must be segregated from all other wiring systems.

• SELV/PELV circuits require no insulation as long as they are separated from the earth.

What are 2 protections against under voltage?

• Over current protection devices

• Alternative Supply

• Under voltage relay

• Over voltage relays

• Temperature sensors

What is the max residual current for RCD's

• 10mA

• 100mA

• 30mA

• 7.5x rated current

On a residential property with more than one subcircuit. What is the max RCBO's?

• 4

• 2

• 1

• 3

What is one limitation on RCD protection in live parts?

• RCDs will always protect against electric shock, even in the case of multiple faults.

• RCDs can protect against both overloads and short circuits in live parts.

• RCD's will not protect a person receiving a shock between active and neutral.

• RCDs only work effectively if the live and neutral conductors are of equal size.

What are the examples of over voltage?

• Voltage surge caused by switching equipment on or off.

• Energising a capacitor bank.

• Lightning discharges on or near an electrical system.

• Transient switching operations.

• A sudden drop in voltage due to a load being switched off.

What are 2 examples of under voltage?

• A sudden surge in voltage caused by a lightning strike.

• Fault in the supply system.

• Starting of large motors.

• Voltage reduction due to a fault in the distribution system.

• A temporary reduction in voltage when a high-power load is switched on.

What are 4 examples of protection against over voltage?

• Fuses.

• Gas filled arrestors.

• Suppression diodes.

• Valve type arrestors.

• Varistor resister.