Тест по High Voltage, Equipment and Testing (CES v5.0)

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Правильні відповіді:
1

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:

Правильну відповідь:

A loose terminal.; Excessive dirt or moisture.; Excessive heat.; A circuit breaker that opened under fault conditions but did not contain the arc.

Ваша відповідь:

Excessive heat.; Inadequate earthing of the cubicle.
2

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?

Ваша відповідь правильна:

That all tools, test equipment and any additional earths have been removed.
3

High voltage switchgear is often provided with busbar shutters. Which one of the following best describes why these are fitted?

Ваша відповідь правильна:

The shutters can be locked to protect against touching the high voltage busbars.
4

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?

Ваша відповідь правильна:

Earthing.
5

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?

Ваша відповідь правильна:

2.
6

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?

Ваша відповідь правильна:

Yes.
7

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?

Ваша відповідь правильна:

A switching plan, approved by the authorised person, must be carried out.
8

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?

Ваша відповідь правильна:

Testing at voltages above the rated voltage will eventually lead to damage to the insulation material.
9

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?

Ваша відповідь правильна:

The guard lead cuts down leakage currents which can give a falsely low insulation reading.
10

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?

Ваша відповідь правильна:

The circuit cannot be energised for testing while a Permit to Work is in force.
11

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?

Правильну відповідь:

It is the ratio of insulation reading obtained after 10 minutes of testing divided by the reading obtained after 1 minute of testing.

Ваша відповідь:

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.
12

When working on high voltage electrical equipment 3 phase portable earthing connectors might be fitted. In what order should these be connected?

Ваша відповідь правильна:

All earthing connectors must be connected to earth before connecting to the circuit to be worked on.
13

Which of the following best describes one of the most important reasons for using high voltage electricity on a ship?

Правильну відповідь:

High voltages may be necessary to limit fault currents to manageable levels.

Ваша відповідь:

High voltages may reduce earth currents to manageable levels.
14

Which of the following is the voltage above which electricity is considered to be high voltage according to this module?

Ваша відповідь правильна:

1 000 Volts AC.
15

Which one of the following best describes a method which can be used to continuously monitor high voltage electrical machinery for insulation condition?

Ваша відповідь правильна:

A partial discharge monitor.
16

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?

Ваша відповідь правильна:

The change should be investigated unless maintenance is known to be responsible for the rise.
17

Which one of the following best describes the function of the insulating hooks often found near high voltage electrical switchboards?

Ваша відповідь правильна:

They are used to remove an unconscious person from areas near high voltage electricity.
18

Which one of the following best describes the main advantage in using high voltage electricity through a “step up” system from low voltage generators?

Ваша відповідь правильна:

Most of the electrical system will operate at familiar voltages.
19

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?

Ваша відповідь правильна:

High voltage allows the azimuth thrusters to be kept small, so reducing hull resistance.
20

Which one of the following best describes the meaning of the term “disconnected” in relation to high voltage electrical systems?

Ваша відповідь правильна:

The connection of power supply to the equipment has been broken.
21

Which one of the following best describes the meaning of the term “tracking” when applied to high voltage electrical systems?

Ваша відповідь правильна:

It is a noticeable current that flows through dirt on the surface of insulation.
22

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?

Ваша відповідь правильна:

Its insulating ability may be permanently reduced.
23

Which one of the following best describes the possible effect of the air between conductors becoming ionised?

Ваша відповідь правильна:

Current arcs can continue to flow after the minimum safe separation is regained.
24

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?

Ваша відповідь правильна:

Anyone can draw up the switching plan but the authorised person must approve it.
25

Which one of the following best describes the reason for “dissipating” charge from high voltage electrical systems?

Ваша відповідь правильна:

Stored electrical charge must be drained away from equipment after it has been “isolated” to make it “discharged”.
26

Which one of the following best describes the role of fresh air within high voltage switchboards?

Ваша відповідь правильна:

Fresh air can be used as an insulator between suitably spaced busbars.
27

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?

Ваша відповідь правильна:

They are allowed to enter an area where access to high voltage equipment is normally restricted.
28

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?

Правильну відповідь:

Large amounts of power can be quickly discharged.

Ваша відповідь:

A small amount of AC power can be discharged.
29

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?

Ваша відповідь правильна:

It must be carefully examined for visual defects before use.
30

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?

Ваша відповідь правильна:

The transformer contains a lot of inductance and may still hold a deadly charge.
31

Which one of the following best describes why high voltage (HV) cables tend to store electrical charge?

Правильну відповідь:

HV systems are made up of two or more parallel conductors, separated by an insulator with a voltage between them, like a capacitor.

Ваша відповідь:

HV cables are made up of many coils of conductor with a voltage between them like a capacitor.
32

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?

Ваша відповідь правильна:

So they are aware of the dangers that have been identified and the safety measures in place.
33

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?

Ваша відповідь правильна:

There are 3 currents created when testing, all of which vary over time.
34

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?

Ваша відповідь правильна:

To make sure it is still working correctly.
35

Which one of the following best describes why someone on a high voltage ship may want to use a “multilock”?

Ваша відповідь правильна:

Multilocks are used where more than one person wishes to ensure that a circuit breaker cannot be operated without their permission.
36

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?

Ваша відповідь правильна:

The prospective earth fault currents on high voltage are much larger and the connection must be large enough not to fuse.
37

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?

Ваша відповідь правильна:

Initially there is a capacitance charging current which shows as a low resistance.
38

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?

Ваша відповідь правильна:

Keep the lock keys to all the isolating breakers under their control.
39

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?

Ваша відповідь правильна:

They should go with the person doing the switching to ensure that the plan has been completed.
40

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?

Ваша відповідь правильна:

The person issuing the Permit to Work.
41

Which one of the following is the best definition of the term “harmonics” when used in relation to high voltage electricity?

Ваша відповідь правильна:

Harmonics are variations in the supply waveform.
42

Which one of the following is the best reason for using thermal imaging equipment during maintenance of a high voltage switchboard?

Правильну відповідь:

To spot heat generated due to a high resistance connection at a cable termination.

Ваша відповідь:

To make sure circuit breaker contacts have cooled before being opened up.
43

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?

Ваша відповідь правильна:

To ensure the motorman does not touch any of the local controls on the switchboards.
44

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?

Правильну відповідь:

The 6,6 kV motor is around one third of the volume of the 440 V motor.

Ваша відповідь:

The 6,6 kV motor is around one tenth of the volume of the 440 V motor.
45

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?

Правильну відповідь:

The Sanction to Test risk assessment may have different safety precautions or PPE requirements; you need to check.

Ваша відповідь:

The safety precautions and PPE requirements will be the same for any electrical permit issued on board.
46

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?

Правильну відповідь:

An Authorised Person may have control over certain parts of the network with overall network control being held by a Senior Authorised Person.

Ваша відповідь:

Only a certified Chief Engineer can be a Senior Authorised Person.
47

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?

Ваша відповідь правильна:

Excessive arcing, overheating, burning and leakage from some types of circuit breaker.
48

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?

Ваша відповідь правильна:

Immediately move away from the live parts, making sure no other persons will be at risk of electrocution.
49

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?

Ваша відповідь правильна:

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.
50

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?

Ваша відповідь правильна:

Do not start work until the authorised person has explained exactly what work is to be done.
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