WorksheetsKnowledge test V2
Total questions: 40
Worksheet time: 3600secs
In a balanced three-phase system, what would be the value of the neutral current?
Line current
3 x phase current
Phase current
Zero
Which piece of network equipment does the following sentence describe?
‘It reduces earth fault current and limits the amount of fault current returning to the transformer’.
A neutral earthing resistor
A switch fuse
A protective multiple earth
A voltage transformer
When considering resistors in a parallel circuit, which statement is correct?
A different potential difference occurs across all resistors
The current in each resistor is equal to its resistance
The same current flows in all resistors
The sum of the currents in the individual resistors is equal to the supply current
For a balanced three-phase system, which ONE of the following is the formula for calculating the PHASE voltage of a STAR connected transformer?
Abbreviations below stand for:
VP – Phase Voltage
VL – Line Voltage
IL – Line Current
Ip – Phase Current
√ - Root 3 (root of three)
VP = IL ÷ Ip
VP = VL
VP = VL ÷ √3
VP = VL - √3
Refer to the Power Factor diagram below. What do the letters A, B and C represent?
A = Apparent Power, B = Real Power and C = Reactive Power
A = Apparent Power, B = Reactive Power and C = Real Power
A = Reactive Power, B = Apparent Power and C = Real Power
A = Reactive Power, B = Real Power and C = Apparent Power
Voltage transformers (VT) can be used for circuit control, safety protection and measurement.
Which ONE of the following describes the principle of VTs operation?
A VT can be used to step up the voltage of the system to a value which is acceptable to the higher rating of meters and relays
A VT can be used to convert the alternating waveform of the system to a direct waveform to supply meters and relays
A VT can be used to step down the voltage of the system to a value which is acceptable to the lower rating of meters and relays
A VT can be used to accept the voltage of the system and connect it directly to the higher rated meters and relays
A transformer which consists of a single winding and is used to step up or step down a constant supply voltage.
What type of transformer is this known as?
Auto-transformer
Current transformer
Voltage transformer
Earthing transformer
Which statement describes the typical method for controlling the output voltage on a 33/11 kV transformer to keep it within its statutory limits?
A control engineer monitors the transformers output voltage and regulates the voltage via an automated tap changer
An automatic voltage control relay monitors the transformers output voltage and regulates the voltage via a tap changer
A current transformer (CT) monitors the transformers output voltage and regulates the voltage via a tap changer
An automated tap changer monitors the transformers output and regulates the voltage via an automatic voltage control relay
The number of secondary windings on a transformer connected to an alternating current (AC) has been decreased.
What effect will this have on the output voltage?
Decrease the input voltage
Decrease the output voltage
Increase the output voltage
Increase the input voltage
What are the typical voltage tolerances for high voltage (up to 132 kV) power networks?
High voltage +6% to -10% of nominal voltage
High voltage ± 3% of nominal voltage
High voltage ± 6% of nominal voltage
High voltage ± 10% of nominal voltage
In a balanced three-phase system with a star-connected load and 10 A line current, what would be the value of the phase current?
10 A
17.3 A
30 A
5.77 A
When considering resistors in a series circuit, which statement is correct?
Different current flows in all resistors
The same potential difference occurs across all resistors
The sum of the potential difference across each resistor is half the value of the supply voltage
The same current flows in all resistors
At what voltage is the transmission of electricity across the UK primarily conducted?
415 V
11 kV
132 kV
400 kV
Which ONE of the following is an example of a ‘Rise in Earth Potential’ (ROEP)?
A ROEP is created by increasing the number of earth electrodes in a substation to prevent system faults
A ROEP is created by bonding all auxiliary steelwork to earth in a substation together to prevent system faults
A ROEP is a phenomenon which occurs during long periods of high voltage switching in a substation which stresses the earth system
A ROEP occurs when a large current flows to earth through the effects of a high voltage fault
In a balanced star-connected three-phase system the value of the phase current:
is higher than the line current
varies above and below the line current
is equal to the line current
is a third less than the line current
Which ONE of the following is an effect produced by a network capacitor bank?
Stores power indefinitely providing an alternative to batteries
Increases line losses and reduces network capacity
Improves voltage drop and regulation on the system
Increases reactive power on system motors and other loads
Which harmonic typically causes neutral current to increase most significantly?
The fifth harmonic
The twelfth harmonic
The seventh harmonic
The third harmonic
In a balanced three-phase system with delta-connected load and 415 V line voltage,
What would the value of the phase voltage be?
0 V
415 V
240 V
440 V
Which ONE of the following describes the primary purpose of the Electricity at Work Regulations 1989?
They aim to prevent the loss of time or production in the process of maintaining an electrical supply in a work environment
They aim to prevent death or injury to any person from electrical causes while working or in a work environment
They aim to reduce death or injury to an acceptable level to any person from electrical causes while working or in a work environment
They aim to improve electrical working practices to provide a more efficient use of tools and equipment in a work environment
Which statement states the principles of maintenance as defined by the Electricity at Work Regulations 1989?
As may be necessary to prevent danger, all systems shall be maintained so as to prevent, so far as is reasonably practicable, such danger
As may be convenient to prevent danger, all systems shall be isolated to prevent injury to operatives working on the system, based on the time and cost of the maintenance operation
As may be necessary to improve performance, all systems shall be maintained on an annual basis to prevent any loss of power to the system
As may be financially viable to prevent danger, all systems shall be maintained so as to prevent, so far as is reasonably practicable, such danger
Which ONE of the following describes the effect of harmonics on a three-phase electrical network?
The networks current and voltage are regulated and conform to their standard sinusoidal waveforms
The networks current and voltage are distorted and deviate from their standard sinusoidal waveforms
The networks current and voltage is increased causing network problems and system faults
The networks current is decreased, and the voltage increased proportionally to regulate their standard sinusoidal waveforms
The regulator Ofgem set targets for the Energy Network Companies.
Which ONE of the following identifies three of the targets?
Customer service, network reliability and environmental performance
Consumer value, economical network design and good waste disposal
Customer communication, network performance and cost reduction
Consumer interaction, network monitoring and reduced wastage
‘A low voltage network which has the neutral bonded to earth at several different points in the system.’
What type of earthing system is the above known as?
Terra Neutral Split system
Protective Multiple Earthing system
Terra Neutral Terra Firma system
Earth Loop Impedance system
The UK’s electricity is typically generated in large commercial power stations.
At what voltage is it generated?
25 kV
132 kV
11 kV
400 kV
Three-phase transformers should only be connected in parallel under which ONE of the following conditions?
When they are identical in all respects
When they have the same secondary voltages
When they have exactly the same losses
When permission is obtained from the manufacturer
Ofgem set price controls on the revenues of Transmission and Distribution Companies using the RIIO model to encourage Companies to consider a number of factors.
What factors do the initials RIIO stand for?
Revenue = Ideas + Implementation + Outlay
Reward = Innovation + Ideas + Outputs
Reward = Input + Investment + Outlay
Revenue = Incentives + Innovation + Outputs
Refer to the diagram shown.
In the order shown, which transformer wiring configurations does this diagram represent?
Three-phase star, three-phase delta
Single-phase star, single-phase delta
Three-phase delta, three-phase star
Single-phase delta, single-phase star
An engineer needs to determine the electrical rating of a switchgear, that will be used on a power network.
What critical factor should the engineer consider?
The manufacturer of the switchgear to be used
The proximity of commercial and domestic buildings
The ability to operate the switchgear manually or remotely
The location of the switchgear in the electrical circuit
In relation to commercial projects, the Construction Design and Management (CDM) Regulations 2015, require that under certain circumstances construction work is notifiable in writing to the HSE.
Which statement identifies ONE of those circumstances?
Where planned construction work will last longer than 20 working days
Where planned construction work will last longer than 30 working days
Where planned construction work will last longer than 40 working days
Where planned construction work will last longer than 50 working days
When considering network protection there are devices that provide an advantage of being able to support overcurrent for a period of time and be reset.
Which device would provide this advantage?
High Rupturing Capacity (HRC) fuses
Contactor relays
Rewireable fuses
Rewireable relays
ERICPD is an acronym used by health and safety organisations as a risk assessment model to help prioritise health and safety measures in the workplace.
What does ERICPD stand for?
Eliminate, Report, Investigate to Control Potential Danger
Eliminate, Remove, Insulate, Caution, Protect and Discipline
Eliminating Risks Insures Complete Protection from Danger
Eliminate, Reduce, Isolate, Control, PPE and Discipline
What would be the effect of a fault on the protection of a low voltage network with a low earth loop impedance value?
The fault current would take longer to activate the protection, the lower the value
The fault current would activate the protection faster, the lower the value
The fault current would activate the protection at the same time regardless of the value
The fault current would not activate the protection if the value was below the UK standard
Which ONE of the following identifies the primary purpose of a risk management strategy?
A risk management strategy provides a cost efficient approach to identifying, assessing, and managing the Company’s financial risk
A risk management strategy provides a timely and effective method of measuring the exposure to risk in the event of an incident
A risk management strategy provides a structured and coherent approach to identifying, assessing, and managing risk
A risk management strategy provides an auditable process which protects a Company from any liability in the event of an incident
A relay operates by the principle that the higher the current value the lesser time it will take the relay to operate. What protocol does this follow?
Immediate Delay Measured Sequence (IDMS) protocol
Inverse Definite Minimum Time (IDMT) protocol
Inverse Decision Time Measure (IDTM) protocol
Individual Delayed Time Sequence (IDTS) protocol
The Construction Design and Management Regulations 2015 (CDM) place certain responsibilities on duty holders involved in the work project to improve health and safety.
Which ONE of following states an aim of the CDM regulations?
To appropriately cost the work so the tasks involved are managed to achieve financial success
To sensibly plan the work so the risks involved are managed from start to finish
To carefully plan the work so the risks involved are kept to a minimum and recorded for audit purposes
To plan the work to ensure the project is delivered within the set timescales
Which ONE of the following describes the typical capabilities of a high voltage switch?
The switch is load making but not load breaking or fault making
The switch is non-load making but is load breaking and fault making
The switch is load making and breaking, and fault making
The switch is non-load making or breaking but is fault making
A ‘permit-to-work’ system is a formal written system used to control certain types of work that are potentially hazardous.
Identify the elements which must be included on a ‘permit-to-work’ document?
Date of issue, description of work, points of contact, signature of document receiver
Date and time of issue, cost of work, points of switching, signature of Company director
Date and time of issue, location of work, points of isolation, signatures of issuer and receiver
Date and time of issue, description of work, points of switching, signatures of the working party
The Electricity Safety, Quality and Continuity Regulations 2002 (ESQCR) places duties to report certain incidents that may involve the safety of those not employed by the duty holder.
Which of the following identifies ONE of these incidents?
Any single interruption of supply of 1 megawatt or more at the time of the interruption for a period of five hours or longer
Any single interruption of supply of 5 megawatts or more at the time of the interruption for a period of one hour or longer
Any multiple interruption of supply of 20 megawatts or more for more than two 5 minutes periods
Any single interruption of supply of 20 megawatts or more at the time of the interruption for a period of one hour or longer
What is meant by the term achieving 'Safety from the System'?
The condition which safeguards persons, tools, equipment, and plant when working near the electrical system
Safeguards that all equipment shall be made dead, prior to any work activities being permitted on the electrical system
The condition which safeguards persons working on or near to equipment from the dangers which are inherent in that system
The condition which safeguards tools and equipment from the dangers of work being conducted on the electrical system
The Electricity Safety, Quality and Continuity Regulations 2002 (ESQCR) place duties on persons to report certain instances.
Which ONE of the following is reportable under ESQCR?
All interruptions to the electricity supply
More interruptions to the electricity supply
Major interruptions to the electricity supply
All planned interruptions to the electricity supply
