Re-take - Useful Information for 2394 :

[amberleaf]

2395-01 . Understand what is being asked of You . ( 1 )

Outcome 1 , Understand the requirements for completing the safe isolation of electrical circuits and installation
You are require to be able :
□ State : the requirements of the Electricity at Work Regulations for the safe inspection of electrical systems and equipment
□ State : specify the appropriate procedure for completing safe isolation
□ State : the reasons for carrying out safe isolation
□ State : the implications of not carrying out safe isolation
□ Identify : the Health & Safety requirements which apply when inspecting , testing and commissioning electrical installations and circuits

Outcome 2 , Understand the requirements for inspection , testing and recording the condition of electrical installations
You are require to be able :
□ State : the purpose of periodic inspection of electrical installations
□ State : the requirements of periodic inspection
□ Identify : the relevant documents associated with the inspection & testing and condition reporting of an electrical installation

Outcome 3 , Understand the requirements for completing the periodic inspection of electrical installations
You are require to be able :
□ Select : appropriate items to be checked during the inspection process
□ Identify : the human senses which can be used during the inspection process
□ State : how the senses can be used during the inspection process
□ Specify the requirements for the inspection of electrical installations in service

Outcome 4 , Understand the difference between periodic inspection and initial verification
You are require to be able :
□ State : the reasons for requiring a periodic inspection as identified in GN-3
□ State : the need to determine the Extent & Limitations of a periodic inspection with the client and interested third parties before work begins
□ Explain : the application of sampling when carrying out periodic inspection & testing to include:

• Factors which determine the extent of sampling
• Situations where sampling may not be appropriate
• Identify the need to record agreements with the client and third parties on the condition report
• Explain the reasons why testing may be undertaken in a different order to that identified in BS-7671: for initial verification
• Identify the considerations which need to be made during a periodic inspection to ensure the safety of the persons & livestock on the premises
• State the purpose of the observations and classification codes in regards to :
□ the observations to be recorded
□ appropriate recommendations to be made

• State the action to be taken if a dangerous situation is identified during the periodic inspection as identified in BS-7671: & GN-3
• Explain the action required by the inspector when the Extent & Limitations agreed may not be achieved on site
• Explain the difference between defects and non-compliances
• Explain why fault finding and remedial work does not form part of the periodic inspection process

Outcome 5 , Understand the requirements for safe testing of electrical installations which have been placed in service
You are require to be able :
□ State : the tests to be carried out during the periodic inspection of an electrical installation in accordance with the BS-7671: & GN-3
□ Identify : the appropriate instrument for each test to be carried out in terms of :
• Checks to confirm the instrument is fit for purpose
• Identifying the right scale / settings of the instrument appropriate to the test to be carried out
□ Specify the requirements for the safe use of instruments to be used for testing and commissioning , to include :
• Checks required to prove that test instruments and leads are safe and functioning correctly
• The need for instruments to be regularly checked and calibrated

 

[amberleaf]

2395-01 . (2)

Outcome 6 , Understand the requirements for testing before circuits are energised
You are require to be able :
□ State : why it is necessary to verify the continuity , to include :
• protective bonding conductors
• circuit protective conductors
• ring final circuit conductors

□ State : the methods for verifying the continuity , to include :
• protective conductors
• ring final circuit conductors
□ Explain : the factors that affect conductors résistance values
□ Specify : the procedures for completing insulation résistance testing
□ State : the effects on insulation résistance values that the following can have :
• Cables connected in parallel
• Variations in cable length
□ Explain : why it is necessary to verify polarity
□ State : the procedures for verifying polarity

Outcome 7 , Understand the requirements for testing energised installations
You are require to be able :
□ State : the method of measuring earth electrode résistance to include :
• installations forming part of a TT system
• Generators and transformers

□ Describe : common earth fault loop paths
□ State : the methods for verifying protection by automatic disconnection of supply
□ Identify : the requirements for the measurement of prospective fault current
□ Specify : the methods for determining prospective fault current
□ Verify : the suitability of protective devices for prospective fault current
□ Specify : the methods for testing the operation of residual current devices
□ State : the reasons for verifying phase sequence
□ State : the methods used to verify phase sequence
□ Describe : the methods used to verify voltage drop
□ State : the cause of voltage drop in an electrical installation
□ Determine : voltage drop
□ State : the need for functional testing
□ Identify : items which require functional testing
□ State : the appropriate procedures for dealing with clients during the periodic inspection process

Outcome 8 , Understand and Interpret test rests
You are require to be able :
□ Explain : why it is necessary to confirm whether test results comply with standard values
□ Analyse test results to determine action to be taken

Outcome 9 , Understand the requirements for the completion of electrical installation condition reports and associated documentation
You are require to be able :
□ Explain : the purpose of an electrical installation condition report
□ State : the information that must be contained within an electrical installation condition report
□ Explain : the requirements for the recording and retention of completed electrical installation condition reports , in accordance with BS-7671:

Outcome 10 , Be able to confirm safety of system and equipment prior to completion of inspection and testing
You are require to be able :
□ Carry out safe isolation procedures in accordance with regulatory requirements
□ Comply with the hearth and safety requirements of themselves and others within the work location during the periodic process
□ Check the safety of electrical systems prior to the commencement of inspection and testing .

 

[amberleaf]

2395-01 . (3)

Outcome 11 , Be able to carry out inspection of electrical installations
You are require to be able :
□ Identify : a safe system of work appropriate to the work activity
□ Carry : out a periodic inspection of an electrical installation in accordance with the requirements of BS-7671: & GN-3
□ Complete a condition Report Inspection Schedule in accordance with the requirements of BS-7671: & GN-3

Outcome 12 , Be able to test electrical installations in service
You are require to be able
□ Select the test instruments and their accessories for tests to include :
• continuity
• insulation résistance
• polarity
• earth electrode résistance
• earth fault loop impedance
• prospective fault current
• RCD operation
• phase sequence
• functional testing

□ Carry : out tests in accordance with BS-7671: & GN-3 to include :
• continuity including
º main protective bonding conductors
º circuit protective conductors
º ring final circuits
• Insulation résistance
• polarity
• earth fault loop impedance ( Ze )
• system earth fault loop impedance ( Zs )
• prospective fault current
• RCD operation including additional protection
• phase sequence
• functional testing
• additional protection
• verification of voltage drop

□ Compare test results with standard requirements and previous test results

Outcome 13 , Produce a condition report with recorded observations and classifications
You are require to be able
□ Use information to determine defects and non-compliances to include :
• dwellings
• other premises
□ Complete Electrical Installation Condition Report and associated documents
□ Handover of the condition report to the client with appropriate information and guidance regarding actions to be taken

 

[amberleaf]

Putting your answers on paper

it is important to remember when you are answering the questions that the examiners cannot ;

• ask you further questions to establish your understanding , they can only award marks for the information you provide .
• assume what you mean or know , they can only interpret the information they are given in your answers .


Test instruments should be calibrated in accordance with the manufacturer's instructions to ensure accurate test results , in addition to calibration which of the flowing should be carried out and recorded .

□ Regular confirmation of the instruments compliance with BS-7671:
□ Extension of the instrument warranty period
□ Regular instrument accuracy checks
□ Closed circuit voltage checks .

Regular instruments accuracy checks are required to ensure the instrument continues to provide accuracy results , as identified in GN-3 , 4.2. if regular checks are not carried out it may result in the need to re-inspect and test earlier installations , once an instrument defect is identified

Which of the following is the maximum voltage above which test leads must comply with the requirements of GS-38
□ 25V a.c.
□ 25V d.c.
□ 50V a.c.
□ 50V d.c.

Where the test voltages are ≤ 50V a.c. the requirement for GS-38 compliant leads is not necessary where the short circuit fault current is unliky to cause a high energy flashover , test current for this test is ≥ 200mA

Which of the following requirements form GS-38 applies to test equipment which requires more than one test lead .
□ The leads must be at least 1m in length
□ The leads must have a CSA of at least 1.5mm[SUP]2[/SUP]
□ The leads must be colour coded for identification ... is the only one of the listed items described in GS-38
□ The leads must be permanently attached to the instrument .

 

[amberleaf]

Remember , What grades . Pass or Fail .

Which of the following instrument must be used to measure the earth electrode résistance for a standby generator .... ◄►( PS keep this in mind )
□ Earth fault loop impedance
□ Insulation résistance tester
□ Low résistance ohmmeter
□ Earth electrode résistance tester .. PS , I no off two Electricians' that got this on 2394.

There is no return path for the current when testing the earth electrode for a transformer or generator , Therefore the test must be undertaken using an Earth electrode résistance tester and not an earth fault loop impedance tester . The other options are not suitable .

Which of the following is not a method used to determine that automatic disconnection of supply for a final circuit is achieved .
□ Direct measurement of ( Zs ) at the furthest point on the circuit
□ Adding the measured value of ( R[SUP]1[/SUP] + R[SUP]2[/SUP] ) the ( Ze ) found by enquiry
□ Adding the measured value ( Ze ) and the measured value of ( R[SUP]1[/SUP] + R[SUP]2[/SUP] ) for the circuit
□ Measuring the prospective fault current at the furthest point on the circuit

Prospective fault current is measured to determine the maximum fault current which may occur at the point where protective devices are installed to ensure they are able to safely disconnect the fault current. Any measurement taken at the end of a circuit will be lower than that at the origin of the circuit and so not the maximum value

The purpose of the measurement of prospective fault current at the origin of an electrical installation is to determine whether
□ The required disconnection time is met
□ The earth fault loop path can withstand the fault current
□ The protective device can safely disconnect the maximum fault current
□ Supplementary earth fault path are required

Prospective fault current is measured to determine the maximum fault current which may occur at the point where the protective device is installed to ensure the device is able to safely disconnect the fault current

Which of the following is not a method for determining prospective earth fault current at the origin of an instrument
□ Enquiry to the DNO
□ Direct measurement
□ Calculation using measured ( Ze ) and the supply voltage
□ Calculation using measured ( Zs ) and the supply voltage

Prospective fault current is measured to determine the maximum fault current which may occur , Any impedance measurement taken at the end of a circuit will be higher than that at the origin of the circuit , As a result the value obtained from the calculation in ( d ) is not going to produce the maximum value

 

[amberleaf]

Yes this Question has been asked on 2394:
PS . there are still in the Regulations BS-3036 fuse

S1A devices are 1KA. in sizes 5 ,15 , 20 , 30 , 45 , & 60A
S2A devices are 2kA. in sizes 5 ,15 , 20 , 30 , 45 , 60 & 100A
S4A devices are 4kA. in sizes 30, 45, 60 & 100A

Q ) Which of the following protective device is never suitable for determining prospective earth fault current at the origin of an installation
□ BS-3036 fuse
□ BS-88-3 fuse
□ BS-88-2 fuse
□ BS-EN-60898-1 circuit breaker .. 6kA / 10kA .

The maximum breaking capacity of a BS-3036 fuse is 4kA , so it is not a suitable protective device where the fault current is 10kA .

• Note : that the devices are available in three types relating to short-circuit capacity, i.e. 1, 2 & 4kA.

Out but not gone . ?? ... BS-3036 fuse

O.S.G. P/72 .
Regulation 533.1.1.3 of BS-7671:2008 refer
states that a fuse shall preferably be of the cartridge type but this does not preclude the use and installation of semi-enclosed fuses. Where a semi- enclosed fuse is selected, the carrier shall be fitted with an element in accordance with the manufacturer’s instructions,

533.1.1.3 permits the fitting of a single element of tinned copper wire of the appropriate diameter specified in Table 53.1 P/140

Terminology
Those fuses referred to as " rewirable fuses " are correctly termed semi enclosed fuses as they are partially enclosed within the fuse-carrier.

semi-enclosed fuse ... BS-3036 fuse
a fuse in which the fuse element is neither in free air ( other than the air in any external containing case not forming part of the fuse ) nor totally enclosed

Rated breaking capacity
BS-3036 defines breaking capacity as: breaking-capacity rating a prospective current stated by the manufacturer to be the greatest

BS 3036 are suitable in certain applications only.
BS 3036 semi-enclosed fuses cannot be relied upon to operate within 4 hours at 1.45 times the nominal current of the fuse element.
Correct protection can be obtained by modifying the normal condition ( In ≤ Iz ) such that the fuse rating does not exceed 1.45 ÷ 2 = 0.725 times the rating of the circuit conductor

For this reason, larger cables may need to be selected where overload protection is provided by semi-enclosed fuses than when it is provided by a cartridge fuse or fuses or circuit-breaker ( Appendix 4 of BS 7671 and Guidance Note 6 give further guidance ). 2008

Fault Current Protection . from my old 16th Edition notes .

The purpose of fault current protection is to disconnect the supply speedily and restrict damage and danger as far as possible .
All parts of an installation must be protected against the highest ( pƒc ) that can be anticipated at any particular point in the system The ( pƒc ) is at is highest at the intake position and will decrease ( or attenuate ) through the installation as the résistance of cables is added to the fault part .

Short Circuit Rating : Under short-circuit conditions there will be a considerable current surge . This is the ( pƒc ) .. for a standard 100A supply the ( PFC ) often quoted by DNO is 16 000A ( kA ) The value is never as high as that .

much depends upon the arrangement of the supply network and the distance from the substation

Rated short-circuit capacity ( Icn ) of the circuit breaker conforming to BS-EN-60898-1 is the value of the ultimate short circuit breaking capacity assigned by the manufacture .

circuit breaker also has a corresponding " in-service " short circuit breaking capacity ( Ics ) which is either equal to , or lower than , the rated short circuit capacity ( Icn )

Conveniently , ( Icn & Ics ) are the same value for circuit breakers conforming to BS-EN-60898 having an ultimate short-circuit capacity of ( 6kA ) or Less .

 

[amberleaf]

Useful junk .

Overcurrent protective device . BS-EN-60898-1
it is only the rated short circuit capacity ( Icn ) that is marked on the circuit breaker 6000A (kA)

Younger members . ( Maximum )
Regulations : specify various maximum disconnection times for different types of circuit(s) for TN - TT - systems

41.3. ( Maximum ) disconnection times
Final circuits not exceeding 32A .. TN - 0.4s .. TT - 0.2s
Final circuits exceeding 32A & for distribution circuits .. TN - 5s .. TT - 1s

from table 41.1. the above values are applicable for a nominal voltage 120V < Uo ≤ 230V

Circuit breaker BS-EN-60898-1 has the characteristics such that it will disconnect the supply in less than 0.1s providing that the maximum earth fault loop impedance permitted by BS-7671: for the circuit being protected is not exceeded .

( PFC ) of an earth fault depends on the maximum earth fault loop impedance at the point of a fault .
if that impedance is lower than the maximum permitted value in Table 41.3. Chapter 41 ... ( Protection against Electric Shock ) disconnection of the supply will occur in less than 0.1s , circuit breaker conforms to BS-EN-60898-1

 

[amberleaf]

2394:
Putting your answers on paper . Due to the time constraints of the exam , do not waste time by copying out the question .
Facts . The markings of your answers does not include any penalties or additional marks for spelling or grammar .

Useful junk .

Overcurrent protective device .
circuit breakers conforming BS-EN-60898-1 is deemed to comply . but there is a need to take account of the increase in temperature and résistance of circuit conductors as a result of overcurrets .

Regulation reminds us . Circuit loop impedance . 612.9. Earth fault loop impedance

Circuit loop impedance given in regulations cover this condition and should not be exceeded where the conductor's are at their normal operating temperature . Regulation reminds us ; if the conductors are at a different temperature when tested , which is usually around ( 20ºC ) the reading should be adjusted accordingly .

This requirement often presents a problem for the person carrying out tests . who is unlikely to be certain of the normal operating temperature . Where this is the case , it is safe to assume the maximum permissible operating temperature of the cable which , in the case of ( thermoplastic PVC ) insulated cables , is ( 70ºC )

2394 : derived for typical test condition's .. View for thought's

Most of your answers are in BS-7671:2011: & GN-3 .

 

[amberleaf]

.. 2014 .

100mA BS-EN-61008-1 RCD is installed in a TT installation to provide fault protection , Which of the following identifies the maximum test current to be applied and the maximum disconnection time at that test current when testing the RCD
□ 100mA & 200mA
□ 100mA & 300mA
□ 500mA & 200mA
□ 500mA & 300mA

The RCD is provided for fault protection and not additional protection and the ( 1 x I∆n ) is the maximum test current that needs to be applied , As this is a BS-EN-61008-1 device the maximum disconnection time is 300mS .

A maximum disconnection time of 200mS applies to some older RCDs manufactured to a British Standard , but not to BS-EN-61008-1 device(s)

Older RCDs .. BS - only .. 200mS
BS-EN-61008-1 .. 300mS

A 30mA BS-EN-61009-1 RCBO is installed on a socket-outlet circuit to provide additional protection , Which of the following identifies the maximum test current to be applied and the maximum disconnection time at that test current .
□ 30mA & 300mA
□ 30mA & 200mA
□ 150mA & 300mA
□ 150mA & 40mS

You're Q . 5 x 30mA = 150mA

The RCBO is provided for additional protection and the ( 5 x I∆n ) is the maximum fault current that needs to be applied . As this device is providing additional protection , the maximum disconnection time is ( 40mS ) as required by BS-7671: Regulation 414.1.1.

 

[amberleaf]

Younger members . in collage
please tell you classmates about this forum . I have did everything but sit your Exam 2394. Amberleaf

 

[amberleaf]

Which of the following is not a suitable method of confirming phase sequence , Read the Question carefully under Exam conditions

□ Measurement using a rotating disc type instrument
□ Measurement using an indicator type instrument
□ Measurement using an approved voltage indicator
□ Checking polarity and connections throughout the installation

the method of determining phase sequence are given in GN-3 , An approved voltage indicator cannot be used to determine phase sequence .

GN-3 . P/57 . PS what can be used . Phase sequence testing . take your Q from above ▲ ▲ ▲
• rotating disc type . Yeah
• indicator lamp type . Yeah

 

[amberleaf]

let's stretch it out a bit .

Q) The purpose of a functional test on an RCD carried out quarterly , using the integral test button , is to confirm

□ The correct functioning of the RCD in the event of a fault
□ That the operation of the RCD complies with BS-7671:
□ That the RCD operates in the event of a short circuit
□ The correct mechanical operation of the RCD mechanism

Operating the RCD test button will only confirm the mechanical operation of the RCD

GN-3 . P/59 . Integral test device .
612.13.1. An Integral test device is incorporated in each RCD , This device enables the functioning of the mechanical parts of the RCD to be verified by pressing the button marked ( T ) or Test

GN-3 . points out some down falls . to watch for . As an Inspector . !! ( Have you Verify )
• The continuity of the earthing conductor or the associated circuit protective conductors Ps RCDs Earth fault . etc
• Any earth electrode or other means of earthing
• Any other part of the associated installation earthing
• The sensitivity of the device .

Point to Remember , Yes we all use Multifunction testers nowadays .

GN-3 P/58 . Operation of residual current devices . 411.4.5.
for each of the tests , readings should be taken on both positive and negative half-cycles and the longer operating time recorded

Point to note : The RCD test button will only operate the RCD if it is energized

 

[amberleaf]

A test is carried out on the interlock for switching an alternative power supply , Which of the following is the type of test being undertaken
□ Functional
□ Continuity
□ Load
□ Installation

This test confirms the operation of the interlocking device and is therefore a , Your Q . Functional test .

 

[amberleaf]

Q) Following a test of earth fault loop impedanc4e ( Zs ) the following results are compared with the values given in BS-7671: Which of the following describes the purpose of the comparison

□ To confirm correct test method are used
□ To confirm conductor csa is suitable for the circuit
□ To determine whether disconnection times will be achieved under earth fault conditions
□ To determine whether the protective devices will operate under short circuit conditions

The operation of a protective device under earth fault conditions relies upon a sufficiently large current flowing , from Ohms Law the supply voltage and impedance of the system will determine the fault current . The ( Zs ) value is the variable and can therefore be used to determine whether disconnection will be achieved within the required time .

 

[amberleaf]

Q) Checking that the measured test results meet the required values will enable the inspector to confirm that the electrical installation is :
□ Correctly installed
□ Safe to be in service
□ Compliant with BS-5266
□ Never going to be dangerous

Providing the test result obtained during the inspection & testing meet the requirements of BS-7671: and the design requirements , the installation will be suitable for use .