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WorksheetsTopic 3 Power Distribution
Total questions: 15
Worksheet time: 8mins
Recall the primary fuel source used by major power plants in Singapore to generate electricity that is transmitted through the national grid.
Coal
Natural gas
Diesel
Hydroelectric
Electricity in Singapore is stepped up for transmission and then progressively stepped down. Which sequence best represents the typical voltage levels from transmission to building distribution?
400V → 22kV → 66kV → 230kV → 400kV
400kV → 230kV → 66kV → 22kV → 400V
230kV → 400kV → 22kV → 66kV → 400V
66kV → 400kV → 230kV → 22kV → 400V
Refer to the Transmission & Distribution System diagram. What is the typical voltage level supplied to low-voltage consumers after the final step-down at the Low Voltage Distribution Panel?
22 kV
6.6 kV
400/230 V
400 kV
Which statement best describes the role of the main switch board in a building’s electrical system?
It is a device used to step up transmission voltage from 230 kV to 400 kV.
It is the distribution and electrical control centre that connects incoming cables and feeds power to boards within the building.
It is a panel dedicated only to lighting circuits and socket outlets.
It is a transformer that converts three-phase 400 V to single-phase 230 V for all equipment.
A distribution board for lights and power points is connected to a single-phase 230 V supply. Which conductor set correctly represents this single-phase connection?
Two phase (live) wires, one neutral wire, and no earth wire
One phase (live) wire, one neutral wire, and one earth wire
Three phase (live) wires, one neutral wire, and one earth wire
One phase (live) wire only, with no neutral or earth
Subsidiary switch boards serving higher-load equipment (e.g., air conditioning systems or lift motor rooms) are typically connected to which supply, and with which conductors?
Single-phase 230 V using one phase, one neutral, and one earth
Three-phase 400 V using three phase wires, one neutral, and one earth
Three-phase 22 kV using three phase wires only
Single-phase 400 V using one phase and one neutral only
In building electrical systems, what is the primary function of a lighting circuit?
To supply power to lighting fixtures for control and illumination
To feed multiple socket outlets and portable appliances
To provide dedicated power for high-load appliances like electric ovens
To regulate voltage from the distribution board to all circuits
Which statement best describes a power circuit in the context of final circuits?
It powers lighting fixtures and dimmers across rooms
It connects to a 20A, 30A, or 32A MCB and supplies several socket outlets and appliances
It is reserved exclusively for emergency lighting and alarm systems
It is limited to loads not exceeding 45 kVA
According to the LEW classifications, which approved load limit applies to a Technician?
Design: not exceeding 150 kVA; Operation: not exceeding 500 kVA
Design: not exceeding 45 kVA; Operation: not exceeding 150 kVA
Design: no limit; Operation: not exceeding 500 kVA
Design: not exceeding 150 kVA; Operation: no limit
Which role is responsible for ensuring electrical installations are safe, reliable, comply with standards, and operate properly, including conducting periodic inspections under EMA governance?
Building supervisor
Licensed Electrical Worker (LEW)
Electrical equipment manufacturer
Resident technician without certification
According to the section on periodic inspection, which authority oversees licensing and renewal compliance for electrical switch rooms and requires inspections to be performed by Licensed Electrical Workers (LEWs)?
Energy Market Authority (EMA)
Ministry of Manpower (MOM)
Public Utilities Board (PUB)
Building and Construction Authority (BCA)
Which component converts the DC electricity produced by solar photovoltaic (PV) panels into AC power usable by a building's electrical system?
Charge controller
Inverter
Battery storage system
AC distribution board
What device is used to protect electrical circuits from overloads and short circuits in a building's electrical system?
Fuse
Transformer
Inverter
Switchboard
Which type of electrical circuit is specifically designed to handle high-power appliances such as electric stoves and dryers?
Control circuit
Lighting circuit
Power circuit
Emergency circuit
In the context of electrical safety, what is the primary purpose of an earth leakage circuit breaker (ELCB)?
To prevent overloading of circuits
To detect and interrupt earth faults
To regulate voltage levels in circuits
To convert AC to DC power
