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家 在线测试 CBT 所有类型的船舶 Ch-Eng / 2nd-Eng Test for seamans about High Voltage, Equipment and Testing (CBT)
在线测试： Test for seamans about High Voltage, Equipment and Testing (CBT)
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A fault within a high voltage starter panel could lead to an explosion. Which of the following is the sort of fault that could cause an explosion? Tick all that apply:
A loose terminal.
Excessive dirt or moisture.
Excessive heat.
A circuit breaker that opened under fault conditions but did not contain the arc.
Inadequate earthing of the cubicle.
Cables bent into too tight a radius.
回答
After maintenance of high voltage equipment has been completed the person carrying out the work is often asked to sign the Permit to Work before the permit is cancelled. Which one of the following best describes what the person is signing for?
To confirm that he knows the permit is cancelled.
That all tools, test equipment and any additional earths have been removed.
To record the time at which he surrendered the permit.
So that the signatures can be compared before and after permit issue.
High voltage switchgear is often provided with busbar shutters. Which one of the following best describes why these are fitted?
The shutters can be locked to protect against touching the high voltage busbars.
The shutters can be locked open to enable visual examination of the busbar condition.
The shutters operate an external indicator which shows whether the breaker is “racked in” or “racked out”.
The shutters help keep dirt off the busbar contacts.
If isolation is not thorough, which of the following is the most dangerous stage in making a piece of high voltage electrical equipment safe to work on, according to this module?
Disconnection.
Reconnection.
Earthing.
Deeding.
Insulation readings for high voltage equipment are sometimes used to calculate a polarisation index. Which one of the following is the value of polarisation index which is normally considered to be the lowest acceptable before investigation of the condition of the insulation is recommended?
2.
4.
5.
1.
Is it possible to get a Sanction to Test permit issued for a piece of high voltage equipment when a Permit to Work has not been issued for that equipment?
Yes.
No.
Maintenance of high voltage equipment has been completed and the Permit to Work cancelled. Which one of the following best describes what needs to be done to put the equipment back into service?
The engine room watch keeper is told that the permit is cancelled and the equipment can be used again.
A switching plan, approved by the authorised person, must be carried out.
The competent person will turn the supply back on before informing the watch keeper.
The competent person will remove the main circuit earth and turn the supply back on before informing the watch keeper.
On low voltage electrical systems insulation is normally tested using voltages above the normal rated supply voltage of the equipment. Which one of the following best describes why high voltage insulation is normally tested using a voltage below the normal rated supply voltage?
Testing at voltages above the rated voltage will eventually lead to damage to the insulation material.
Insulation testers cannot produce high enough voltages from batteries.
Testing at voltages above the rated voltage is too dangerous.
Testing at voltages above the rated voltage can generate high static charges.
Some insulation test meters for high voltage equipment are fitted with a 3rd lead, often called a “guard”. Which one of the following best describes the reason for using the guard lead?
The guard lead cuts down absorption currents which can give a falsely high insulation reading.
The guard lead cuts down the risk of electrocution from the meter.
The guard lead cuts down leakage currents which can give a falsely low insulation reading.
The guard lead is used to check for a good earth connection.
The electrician has been issued with a Permit to Work on the high voltage thruster starter. Which one of the following best describes why he may also require a Sanction to Test Permit?
The circuit cannot be energised for testing while a Permit to Work is in force.
High voltage insulation testers are very expensive and can only be issued by the stores to someone holding a Sanction to Test Permit.
No testing of any kind is allowed on high voltage systems without a Sanction to Test Permit.
A Sanction to Test is needed when testing high voltage circuits which run outside the main engine room.
When measuring the insulation resistance of high voltage equipment, a “polarisation index” test may be used. Which one of the following best describes what a “polarisation index” is?
It is the ratio of insulation reading obtained after 10 minutes of testing divided by the reading obtained after 1 minute of testing.
It is the ratio of insulation reading obtained after 1 minutes of testing divided by the reading obtained after 10 minute of testing.
It is the angle between the central axis of a rotor and the indicated North of a compass needle while a test voltage is applied to the rotor windings.
It is the strength of polarising lens that is necessary to see the magnetic field of the equipment under test.
When working on high voltage electrical equipment 3 phase portable earthing connectors might be fitted. In what order should these be connected?
The earthing connectors must be connected to Red, then Yellow, then Blue phases.
All earthing connectors must be connected to the circuit to be worked on before connecting to earth.
All earthing connectors must be connected to earth before connecting to the circuit to be worked on.
It makes no difference.
Which of the following best describes one of the most important reasons for using high voltage electricity on a ship?
High voltages may be necessary to limit fault currents to manageable levels.
High voltages may reduce earth currents to manageable levels.
High voltages may increase the power of main electric propulsion motors.
High voltages may remove the need for the use of DC in high power systems.
Which of the following is the voltage above which electricity is considered to be high voltage according to this module?
1 000 Volts AC.
1 000 Volts DC.
3 000 Volts AC.
250 Volts AC or DC.
Which one of the following best describes a method which can be used to continuously monitor high voltage electrical machinery for insulation condition?
A partial discharge monitor.
Earth lights.
A power factor meter.
A vibration monitor.
Which one of the following best describes the action to take if the polarisation index calculated from insulation readings on a piece of high voltage equipment has risen by 35 % in 6 months?
Pat yourself on the back for a good job done.
Take the readings again, there must be a mistake.
Send an e-mail to the company telling them the new insulation meter is better than the old one.
The change should be investigated unless maintenance is known to be responsible for the rise.
Which one of the following best describes the function of the insulating hooks often found near high voltage electrical switchboards?
They are used to remove an unconscious person from areas near high voltage electricity.
They are used to dissipate high voltage electricity.
They are used to test high voltage conductors to see if they are dead.
They are used to form a barrier between workers and nearby high voltage sources.
Which one of the following best describes the main advantage in using high voltage electricity through a “step up” system from low voltage generators?
Most of the electrical system will operate at familiar voltages.
Low voltage generators are smaller than high voltage ones.
A high voltage fault cannot affect the essential low voltage consumers.
Most of the system is made up of low voltage components which are cheap.
Which one of the following best describes the main reason why the azimuth thrusters used for propulsion on some ships are normally supplied with high voltage electricity?
High voltages remove the need for transformers to be installed on the ship.
High voltage allows the azimuth thrusters to be larger, so a larger propeller can be fitted.
Azimuth thrusters are only fitted on passenger ships where high voltage is available.
High voltage allows the azimuth thrusters to be kept small, so reducing hull resistance.
Which one of the following best describes the meaning of the term “disconnected” in relation to high voltage electrical systems?
The connection of power supply to the equipment has been broken.
The power supply cables to the equipment have been removed from the contactor terminals and taped up.
The equipment is safe to work on.
There is an open circuit in at least one supply conductor to a piece of equipment.
Which one of the following best describes the meaning of the term “tracking” when applied to high voltage electrical systems?
It is a noticeable current that flows through dirt on the surface of insulation.
It is the method of securing busbars within a switchboard.
It is a current that flows within insulation layers.
It is the method of separating busbars within a switchboard.
Which one of the following best describes the possible effect of supplying a solid insulator with a voltage above that for which it was designed?
Its insulating ability will only be temporarily reduced.
Its insulating ability may be permanently reduced.
Its insulating ability will not be affected provided that the voltage is no more than 150 % of the rated voltage.
Its insulating ability can be temporarily improved.
Which one of the following best describes the possible effect of the air between conductors becoming ionised?
Current arcs can continue to flow after the minimum safe separation is regained.
Current arcs can form if the conductors move towards each other.
“Ball” arcs can appear.
Cable insulation can become cracked as the ionisation effects its make-up.
Which one of the following best describes the process of drawing up and implementing a switching plan when connecting or disconnecting high voltage electrical equipment?
Anyone can draw up the switching plan but the authorised person must approve it.
The authorised person must draw up the switching plan.
The authorised person must draw up the switching plan but the chief engineer must approve the plan.
The component person must approve the switching plan.
Which one of the following best describes the reason for “dissipating” charge from high voltage electrical systems?
A charge must be applied to equipment in order to test its function.
A charge must be applied to equipment in order to test its insulation resistance.
Stored electrical charge must be drained away from equipment after it has been “isolated” to make it “discharged”.
A charge must be transferred to the equipment using transformer action between coils.
Which one of the following best describes the role of fresh air within high voltage switchboards?
Fresh air can be used as an insulator between suitably spaced busbars.
Fresh air is used to cool high voltage circuit breaker contacts during faults.
Fresh air is often removed from high voltage switchboards to create a vacuum.
Fresh air is often dried before being supplied to high voltage switchboards.
Which one of the following best describes what someone issued with a Limitation of Access Permit is allowed to do in relation to high voltage electrical systems?
They are allowed to enter an area where access to high voltage equipment is normally restricted.
They are allowed to enter and operate equipment within a restricted high voltage switchboard room.
They are allowed to enter engine rooms containing high voltage propulsion motors.
They are allowed to climb on top of high voltage equipment which is more than 2 metres high.
Which one of the following best describes what will happen if a low impedance connection is accidently created across a charged capacitor within a high voltage electrical network?
A small amount of AC power can be discharged.
A large amount of AC power can be stored.
Large amounts of power can be quickly discharged.
A small leakage current will flow.
Which one of the following best describes what you should do after you have got together the protective, test or other equipment which is to be used during work on a high voltage electrical system?
It must be carefully examined for visual defects before use.
It must all have a test certificate which was issued less than 12 months before.
Personal protective equipment must have its insulation resistance checked in at least 2 places per item.
Test equipment must have its batteries checked.
Which one of the following best describes why extra care should be taken when preparing a high voltage transformer circuit to be worked on after it has been fully isolated?
The transformer contains a lot of inductance and may still hold a deadly charge.
The transformer contains a lot of capacitance and may still hold a deadly charge.
The transformer may be supplied from high voltage and low voltage sides.
High voltage transformers are normally oil filled and may leak toxic oil.
Which one of the following best describes why high voltage (HV) cables tend to store electrical charge?
HV cables are made up of many coils of conductor with a voltage between them like a capacitor.
HV systems are made up of two or more parallel conductors, separated by an insulator with a voltage between them, like a capacitor.
The insulation on HV cables is softer than for low voltage and creates static charge.
The insulation on HV cables is harder than for low voltage and holds a static charge.
Which one of the following best describes why it is important for someone to read the detailed risk assessment for the job before they start work on high voltage equipment?
So they can see exactly what they need to do to complete the job efficiently.
So they can see who should issue the Electrical Permit to Work.
So they are aware of the dangers that have been identified and the safety measures in place.
So they can see if a Limitation of Access Permit will be required.
Which one of the following best describes why it is necessary to record insulation readings taken from high voltage equipment after a fixed period of test time?
There are 3 currents created when testing, all of which vary over time.
It is advisable to ensure any undetected charge has decayed before taking a reading.
The electronics within the meter need to warm up before an accurate reading is produced.
The equipment gets warm while the test current is present, so changing the reading.
Which one of the following best describes why it is normal practice to place the high voltage (Hi-pot) tester back in its test until after a circuit has been tested as being dead?
To protect the ceramic end of the tester.
To make sure it is still working correctly.
To make sure the test unit reading agrees with the circuit reading.
To make sure the test unit batteries are still working.
Which one of the following best describes why someone on a high voltage ship may want to use a “multilock”?
Multilocks are used where more than one person wishes to ensure that a circuit breaker cannot be operated without their permission.
Multilocks are used so all padlocks on circuit breakers can be opened by the same key.
Multilocks are used where more than one size of circuit breaker is required to be locked using a standard size lock.
Multilocks have long wires so that more than one switch can be locked off with a single lock.
Which one of the following best describes why the earth connections applied to high voltage circuits while maintenance is being carried out are of much larger diameter than those typically used in low voltage lighting circuits?
The prospective earth fault currents on high voltage are much larger and the connection must be large enough not to fuse.
Earth faults on high voltage need larger diameter earth connections with low resistance to allow the current to flow freely.
The earth connections must be the same diameter as the current carrying conductors being earthed in both cases.
Owners of high voltage systems can afford the more expensive, thicker copper earth connections.
Which one of the following best describes why, when taking insulation readings from high voltage cables, the reading is poor to start with but usually gets better quite quickly?
The cable insulation gets warm while the test current is present, so changing the reading.
The test current takes a while to stabilise as the meter batteries build up a high voltage output.
Initially there is a capacitance charging current which shows as a low resistance.
The electronics within the meter need to warm up before an accurate reading is produced.
Which one of the following describes the best way for the person assigned to carry out work on high voltage equipment to ensure that the equipment will remain dead until their Permit to Work is withdrawn?
Keep the lock keys to all the isolating breakers under their control.
Keep the lock keys to all the isolating breakers in the control room.
Take the control fuses out of all the isolating breakers.
Disconnect the output cables from all the isolating breakers.
Which one of the following describes the best way for the person assigned to carry out work on high voltage equipment to ensure that the switching plan has been properly carried out?
They should check the signature of the person doing the switching is on the Permit to Work.
They should go with the person doing the switching to ensure that the plan has been completed.
They should check the signature of the person doing the switching is on the Sanction to Test.
They should count the number of keys in the electrician’s key safe.
Which one of the following is normally the first person to touch the conductors of high voltage equipment after they have been made safe to work on?
The person issuing the Permit to Work.
The person issuing the Limitation of Access Permit.
The Competent Person.
The senior engineer on watch.
Which one of the following is the best definition of the term “harmonics” when used in relation to high voltage electricity?
Harmonics are variations in the supply waveform.
Harmonics are caused by circuit breakers opening and closing repeatedly.
Harmonics are vibrations in the supply cables which can crack insulation.
Harmonics are the noise made by certain high voltage generators.
Which one of the following is the best reason for using thermal imaging equipment during maintenance of a high voltage switchboard?
To make sure circuit breaker contacts have cooled before being opened up.
To check the temperature of the incoming and outgoing cable insulation.
To spot heat generated due to a high resistance connection at a cable termination.
To check the ambient temperature within the switchboard while it is in service.
Which one of the following is the main reason why you may be sent to stay with the motorman while he paints the high voltage switchboard room?
To ensure the motorman does not touch any of the local controls on the switchboards.
To ensure that the switchboards are properly covered against paint splashes.
To ensure that no paint is allowed to enter the switchboard vents.
To ensure that any warning signs are put back exactly where they were before painting.
Which one of the following options correctly indicates the difference in size between an 800 kW electric motor supplied at 6,6 kV and another 800 kW electric motor supplied at 440 V?
The 6,6 kV motor is around three times of the volume of the 440 V motor.
The 6,6 kV motor is around one tenth of the volume of the 440 V motor.
The 6,6 kV motor is around one third of the volume of the 440 V motor.
They are the same volume.
While conducting maintenance on a high voltage transformer you need to swap your Permit to Work for a Sanction to Test Permit. Which one of the following best describes the position at the time of changeover between permits?
The Sanction to Test risk assessment may have different safety precautions or PPE requirements; you need to check.
The safety precautions and PPE requirements will be the same for both permits.
The safety precautions and PPE requirements will be the same for any electrical permit issued on board.
The Sanction to Test risk assessment may have different safety precautions but the PPE requirements will be the same.
With regard to the management of high voltage electrical systems, which one of the following best describes the difference between an “Authorised Person” and a “Senior Authorised Person”, as stated in this module?
Only a certified Chief Engineer can be a Senior Authorised Person.
An Authorised Person may have control over certain parts of the network with overall network control being held by a Senior Authorised Person.
Senior Authorised Persons need to reach the standards set out in STCW for electrical officers and Authorised Persons can be engineers.
An Authorised Person can become a Senior Authorised Person after 18 months sea service.
You are carrying out an internal examination of a high voltage switchboard. Which one of the following best describes the faults that might be detected using your sense of smell?
Excessive arcing, overheating, burning and leakage from some types of circuit breaker.
Insulation breakdown, excessive voltage.
Tracking.
Loose connections, wrong type of terminations used.
You have been appointed the Competent Person for checking a high voltage distribution cable. While accompanying the authorised person, you see that the high voltage (Hi-pot) tester shows a voltage is present when the cable is tested to see if it is dead. Which one of the following best describes the action you should take?
Get the authorised person to test the Hi-pot tester in its test unit.
Immediately move away from the live parts, making sure no other persons will be at risk of electrocution.
Change the batteries in the Hi-pot tester.
Keep the Hi-pot tester in place until the voltage dissipates, or for 2 minutes, whichever is shorter.
You have been appointed the Competent Person for checking a high voltage motor of a cargo pump. While accompanying the Authorised Person you see that the high voltage (Hi-pot) tester shows a voltage is present when the motor is being tested to see if it is dead. The voltage falls away to zero within 2 seconds. Which one of the following best describes what you should do before signing the Permit to Work to say that you are satisfied with the safety arrangements?
You should ask for the motor to be retested before you sign the permit, even though the reading indicates the probable successful dissipation of inductive charge.
You should check the batteries in the Hi-pot tester test unit.
Your ship has been sent a circular from the company warning of problems on the distribution boards on your sister ship. You have been issued with a Permit to Work for the port aft high voltage distribution board but you are not sure what needs to be done. What should you do?
Ask the 2nd Engineer if he has read the circular before starting work.
Carry out the normal annual planned maintenance checks on the distribution board.
Do not start work until the authorised person has explained exactly what work is to be done.
Open up the distribution board and use your eyes and ears to try to find the problem.
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