18th Edition - Quiz 1
18th Edition Essentials Check
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BS7671 applies to?
Equipment on board ships
Lighting protection of buildings
Lift installations
Prefabricated buildings
BS7671 provides requirements for safety against the risk of?
Electric shock on an aircraft
Shock currents on board ships
Fire on offshore installations
Shock currents in electrical installations
Which one of the following is not a statutory regulation?
Electricity at Work Regulations 1989 as amended
The Supply of Machinery (Safety) Regulations 1992 as amended
Requirements for Electrical Installations (BS7671)
Agricultural (Stationary Machinery) Regulations
BS7671 identifies that the cross-sectional area of a conductor shall by determined by?
The admissible maximum temperature
The nominal voltage
Voltage tolerances
The earthing system
A corridor containing supporting structures for cables and joints and/or other elements of wiring systems, the dimensions of which allow persons to pass freely throughout the entire length, is known as?
An access pathway
A cable tunnel
An access throughway
Cable ducting
The algebraic sum of the currents in the live conductors of a circuit at a point in the electrical installation is known as?
Residual current
Harmonic current
Line current
Neutral current
With reference to the nature of the supply, which one of the following can be determined by calculation, enquiry or measurement?
The maximum demand of the installation
The rating of the circuit protective device
The prospective short-circuit current at the origin of the installation
The csa of the tails
Every installation should be divided into individual circuits to?
Prevent faults developing
Provide protection against electric shock
Minimise inconvenience in the event of a fault
Ease installation
Diversity may be taken into account when considering?
Maximum demand of the installation
A TN-C-S system
The prospective short-circuit fault current
The number of final circuits
Which one of the following is not a characteristic of the supply?
The nature of the current and frequency (ii)
The earth fault loop impedance external to the installatin
Main switch current rating
The nominal voltage
BS7671 requires designers to take into account the frequency and quality of maintenance an installation can reasonably be expected to receive when?
Assessing staff numbers
Inspecting and testing
Specifying or selecting equipment reliability
Specifying or selecting equipment reliability
Which one of the following is not part of the requirements for fault protection?
Protective earthing
Protective equipotential bonding
Automatic disconnection
Protection by insulation of live parts
The maximum disconnection time for a TN system with a nominal voltage of 400 V AC to Earth is?
0.2 seconds
0.4 seconds
1 seconds
5 seconds
For a TT system, which one of the following conditions should be fulfilled for each circuit protected by an RCD?
RA x IΔn ≤50 V
RA x lΔn ≥ 50 V
RA x ld ≤50 V
RA x ld ≤50 V
A 32 A type B circuit-breaker is used to give a disconnection time of 5 seconds in a reduced low voltage system with a nominal voltage to Earth (Uo) of 55 V. What is the maximum value of earth fault loop impedance (Zs)?
0.44 Ω
0.17 Ω
0.09 Ω
0.33 Ω
A SELV source can be derived from which one of the following?
Double-wound transformer
Autotransformer
Safety isolating transformer
Step-up transformer
Which one of the following cannot be used as basic protection?
Insulation of live parts
Barriers or enclosures
Obstacles Reg
Protective earthing and bonding
In order to provide basic protection, a horizontal top surface of a barrier or enclosure that is readily accessible shall provide a minimum degree of protection of?
IPXXA or IP1X
IPXXB or IP2X
IPXXC or IP3X
IPXXC or IP3X
Where arcs, sparks or particles at high temperature may be emitted by fixed equipment in normal service, the equipment shall be?
Protected by a 30 mA RCD
Totally enclosed in arc-resistant material
Accessible only by use of a key or tool
Enclosed to at least IP55