Re-take - Useful Information for 2394 :

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What is insulation résistance ??

GN-3 . /39
The purpose of the insulation résistance test is to verify that the insulation of conductors' provides adequate insulation , is not damaged and that live conductor's or protective conductor's are not short-circuited .

 

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2395-302 Chief Examiners Report . ◄ refer to .

learn by mistakes .

When asked why the earthing conductor must be connected to the installation earthing system during a prospective fault current test, common answers given by candidates included that it would be dangerous if it wasn't connected and you would not be able to carry out the test if it wasn't connected.

Few candidates appreciated that the earthing conductor would be connected when a fault occurred and the parallel paths would increase the level of fault current that would flow, and it is this maximum value that must be determined during the test.

Chief Examiners' 2394 . (13)

Testing

When asked to explain why an earth fault loop impedance test needed to be carried out on existing circuits after a board change,
many candidates failed to state that the protective devices for these circuits would have changed

Few answers identified the need to confirm that the maximum earth fault loop impedance values was not exceeded in order to ensure the appropriate disconnection times would be met in the event of an earth fault.

Some candidates had difficulty explaining why the earthing conductor must be disconnected from the installation earthing arrangements during a measurement of external earth fault loop impedance. Most answers included comments relating to the removal of parallel paths, but

answers indicated the need to confirm the intended external path was effective. from the installation earthing arrangements during a measurement of external earth fault loop impedance. Most answers included comments relating to the removal of parallel paths, but

► few answers indicated the need to confirm the intended external path was effective. ◄◄◄

 

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C&Gs have asked this question many times .. & will not stop asking

Question on earth electrode testing . ( One method ) not typing out two pages . sorry

GN-3 2008: ◄► P/46
Earth electrode résistance . example .

Measurement by standard method
When measuring earth-electrode-résistances to earth where low values are required as in the earthing of the neutral point of a transformer or generator , test method 1 below may be used

Instrument used as earth electrode résistance tester for this test .

Test method 1
before this test is undertaken , the earthing conductor to the earth-electrode must be disconnected either at the electrode or at the main earthing terminal to ensure that all the test current passes through the earth-electrode alone

Note : This will leave the installation unprotected against earth-faults . ◄◄ safety

Note : After completion of the Testing ensure that the Earthing-conductor is Reconnected. ◄◄ safety

GN-3 2011: ◄
Earth electrode résistance testing .
Three methods' of measuring the résistance of an earth-electrode. refer . Test method E1 , Test method E2 , Test method E3 . ▼

GN-3 2008: Earth electrode for RCDs .
if the electrode under test is being used in conjunction with a residual current device the following method of test may be applied as an alternative to the earth electrode résistance test . where the electrical résistance to earth are relatively high& precision is not required , an earth fault loop impedance tester may be used .

TT- systems always get heads turning in Exams .

with TT - systems C&Gs are looking for safety at all times .

 

[Richard Burns]

Chief Examiners' 2394 . (12)
The final question on the paper required the candidate to describe an (earth fault loop path) for the system given in the scenario.
Many diagrams were incomplete.
Candidates failed to identify the component parts of the earth fault loop path and so lost considerable marks. A large number of marks are allocated to the labelling, or identifying in a written description, the component parts of the earth fault loop path as indicated in GN 3.

GN3 states the following elements of the earth fault current loop path:
The circuit protective conductor
The main earthing terminal and earthing conductor
For TN systems the metallic return path or for IT or TT systems the earth return path
The path through the earthed neutral point of the transformer
The source line winding
The line conductor from the source to the point of the fault

These are example diagrams with the parts of the EFLI identified as well, for understanding (Zs, Ze, R1, R2, R1+R2)

 

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Thank you . You.r a Star Richard . Outstanding . my friend .
This is what it is all about . A better understanding . 100%

 

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Useful Junk .

Residual current devices ( RCDs ) in TN systems

For a circuit using an RCD for fault protection, Regulation 411.4.5 requires that the product of the earth fault loop impedance (Zs) and the rated residual operating current ( I∆n ) of the RCD does not exceed Uo volts (V)
therefore follows that the maximum permitted value of (Zs) is given by equation : ( Zs = Uo / I∆n ) Ω

Where: ( I∆n ) is the rated residual operiting current of the RCD in amperes .

For a circuit of nominal voltage Uo 230 V supplied through an RCD having a rated residual operating current ( I∆n ) of 100mA (0.1 A), the maximum permitted value of (Zs) produced by equation : is 2300 ( 230 V 0.1 A ) = 2300Ω

100mA ÷ 1000 = 0.1A

10mA ÷ 1000 = 0.01A
30mA ÷ 1000 = 0.03A
300mA .
500mA . Etc

 

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" Continuity " Small rant .

(i) O.S.G. P/90 / 91 . 10.3.1.
(ii) GN-3 . 2.7.6. Continuity of ring final circuit-Conductor(s)
612.2.2. A three-step test is required to verify the ( Continuity ) of the , Line , Neutral , & Protective-conductors .

Step 1 . is end-to-end ( Ω ) measure the résistance of each Ring / Loop .. Identify
( Certification ) R/P.402 .. Schedule of test results . Ring final circuit continuity ( Ω ) 10 , 11 , 12 . Little ( r [SUP] 1 N 2[/SUP] )

Measurements taken at the Origin of an ( A1 ring circuit 100m[SUP]2[/SUP] ) O.S.G. table H2.1.
( r[SUP]1 [/SUP] = 0.4Ω ) .. T&E
( r[SUP]N [/SUP] = 0.4Ω ) ..
( r[SUP]2[/SUP] = 0.67Ω ) ..

Determine the measured value of résistance ( at each socket-outlet ) ends of the circuit are cross connected to form a ( Figure of 8 )

( Figure of 8 ) Step 2 . Connections for testing , Line & Neutral .
( Figure of 8 ) Step 3 . Connections for testing , Line & Circuit-protective-conductor . CPC

cross connection between Line & Neutral at origin ... measure résistance between Line & Neutral at each socket
cross connection between Line & CPC at origin ... measure résistance between Line & Circuit-protective-conductor at each socket

recap . GN-3 . tells us .

Line & Neural is measured at each socket-outlet , The ( Readings ) obtained at each of the sockets wired into the ring will be substantially the same & the value will be approximately one-quarter of the résistance of the line plus , CPC loop résistance . ( r[SUP]1 [/SUP]+ r[SUP]2[/SUP] ) / 4 .

Line & Earth is measured at each socket-outlet , The ( Readings ) obtained at each of the sockets wired into the ring will be substantially the same & the value will be approximately one-quarter of the résistance of the line plus , CPC loop résistance . ( r[SUP]1 [/SUP]+ r[SUP]2[/SUP] ) / 4 .

( r[SUP]1 [/SUP]+ r[SUP]N [/SUP]= 0.4 + 0.4 = 0.8 ÷ 4 = 0.2Ω ) line & neutral
( r[SUP]1 [/SUP]+ r[SUP]2 [/SUP]= 0.4 + 0.67 = 1.07 ÷ 4 = 0.267Ω ) line & circuit-protective-conductor .

The highest value recorded represents the maximum ( R[SUP]1[/SUP] + R[SUP]2[/SUP] ) of the circuit & is recorded on the Schedule of test results .

Note : A higher résistance value will be recorded at any ( socket-outlets wired as Spurs )

Note : R/P.402 . Where there are no spurs connected to the ring-final-circuit this value is also the ( R[SUP]1[/SUP] + R[SUP]2[/SUP] ) of the circuit .

The other test confirmed is : Polarity by Continuity method .

Three specific requirements for ( Verification ) of polarity with the regard to ( Accessories )
612.6. Polarity
(i) All single-pole devices are connected in the line conductor only .
(ii) The centre contact of Edison screw lamps . refer . ( LED lights are taken centre stage now ) 2 Dee ,
(iii) Wiring has been correctly connected to socket-outlets & similar accessories

( R[SUP]1[/SUP] + R[SUP]2[/SUP] ) am single narrowed out ( R[SUP]2[/SUP] ) what has you achieved , you have verified , by test that must be carried out to confirm that your circuit-protective-conductors are continuous throughout you loop . .. under earth-fault-conditions your RCD will take it out

( R[SUP]1[/SUP] + R[SUP]2[/SUP] ) am single narrowed out ( R[SUP]1[/SUP] ) what has you achieved , you have verified , by test you carried out to confirm that your line-conductors are continuous throughout your loop . *

612.6. Polarity
(i) All single-pole devices are connected in the line-conductor only * Circuit-breaker or RCBO . etc

GN-3 & BS-7671: have their merits of each test . nock on affect .

 

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State the action to be taken regarding the Earthing-conductor before measuring the résistance of an earth-electrode .
( Earth electrode testing ) ... Do not disconnect any protective-conductors before ( Isolating the supply )

Disconnect earthing conductor at ( MET ) to avoid parallel earth paths .

GN-3 : 2.7.12. Q/As

recap . Test method 1 .
before test is undertaken , the earthing-conductor to the earth-electrode must be disconnected either at the electrode or the ( MET ) to ensure that all the test current passes through the earth electrode alone .

This will leave the installation unprotected against earth faults .

 

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Useful Junk

Any surface potential ( V )

The potential ( V ) arising on an installation earth-electrode under earth fault conditions will have a value relative to the nominal voltage to Earth of the supply ( Uo ) as follows:

V = Uo x R[SUP]A[/SUP] / Zs (V )

Where :
( Uo ) is the normal voltage of the supply
( R[SUP]A [/SUP]) is the sum of the resistances of the earth electrode and the protective conductor connecting it to the exposed-conductive-parts
( Zs ) is the earth fault loop impedance of the faulty circuit

For example , suppose an earth fault of negligible impedance has occurred in a circuit of an installation in a TT system and suppose the nominal voltage of the supply ( Uo ) is 230V, the earth fault loop impedance ( Zs ) is 100Ω and the earth electrode resistance is 80Ω.

By substituting these values into equation : V = 230V x 80Ω ÷ 100Ω = 184V

it is found that the potential ( V ) appearing at the earth electrode is 184 V.

the duration over which the potential exists must be considered, account being taken of the fact that persons or livestock will generally be in contact with the general mass of Earth .

 

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Changes to existing electrical installations, such as additions or alterations

Regulation . 132.16 . What are they asking us for . Simple . Assessment of an Existing Installation

‘ No addition or alteration, temporary or permanent, shall be made to an existing installation, unless it has been ascertained that the rating and the condition of any existing equipment, including that of the distributor, will be adequate for the altered circumstances. Furthermore,

the earthing and bonding arrangements, if necessary for the protective measure applied for the safety of the addition or alteration, shall be adequate ’.

 

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Means of earthing :
The means of earthing is the arrangement through which a connection is made to the general mass of Earth .

 

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On small rant mode . Chief Examiner's report

Examples Only , Scenarios

• Additional lighting point (luminaire and/or switching) on a single existing circuit.
- Minor Works Certificate may be used provided the existing circuit protective device is suitable for protection of the modified circuit, and other safety provisions are adequate

Changes to existing electrical installations, such as Additions or Alterations . your Q . Overlooked
Existing circuit protective device is suitable for protection of the modified circuit .. make a statement

Chief Examiner's report , 2394 , lost marks
• Additional socket-outlet on a single existing radial or ring circuit
- Minor Works Certificate may be used provided the existing circuit protective device is suitable for protection of the modified circuit, and other safety provisions are adequate

• Replacement of an accessory, such as a socket-outlet or a ceiling rose, on a like-for-like basis

Changes to existing electrical installations, such as additions or alterations

( MEIWC ) Part 2 Installation details .
( 3 ) Protective devices for the modified circuit ... ( Type ........ Rating ....... A ) ◄◄◄ ( Protective devices )

Examples of work that falls within the scope of a Minor Electrical Installation Works Certificate . R/P.394

• the addition of a socket-outlet to a ring or radial final circuit
• work carried out on a lighting final circuit, including an alteration to the switching arrangements
• the addition of a lighting point or
• the replacement of an accessory or luminaire

work considered to fall within the scope of the Minor Electrical Installation Works Certificate, refer to the Minor Electrical Installation Works Certificate.

Note : that for the provision of a new circuit, the Electrical Installation Certificate must be used; Not the Minor Electrical Installation Works Certificate.

R/P. 196 , Any defects or omissions in the work covered by the Electrical Installation Certificate or the Minor Electrical Installation Works Certificate must be made good before the Certificate is issued ( Regulation 632.4 ) and before the installation is energised.

Minor Electrical Installation Works Certificate may be used only
where the work involves an alteration or an addition to an existing single circuit and where the work does not entail the provision of a new circuit .

Verification of the means of earthing
the earthing and bonding arrangements, if necessary for the protective measure applied for the safety of the addition or alteration, shall be adequate ’.

 

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How hard can it BE ??? 2394 / 5 .

Unit 301 - Multiple choice examination . 2013 / 14 .

This examination covers areas of knowledge & understanding which are common to both ( Initial verification ) & ( Periodic inspection )
This assessment is the same assessment for both qualifications & learners need only achieve the test once .

40 questions & 1 hour 20 minutes long ... Closed book examination

Outcome:
Understand the requirements for completing the safe isolation of electrical circuits & installation(s) .. N/questions ( 7 ) (%) - 18
Understand the requirements for inspection & testing of electrical installation(s) .. N/questions ( 2 ) (%) - 5
Understand the requirements for safe testing electrical installation(s) .. N/questions ( 11 ) (%) - 27
Understand the requirements for testing circuits which are not energised .. N/questions ( 7 ) (%) - 18
Understand the requirements for testing energised installation(s) .. N/questions ( 13 ) (%) - 32
Total .. N/questions ( 40 ) (%) - 100

Unit 302 - Written Examination
The examination papers for both qualifications ( 2394 & 2395 ) have the same format , They each have ( 6 structured ) qualifications & are 1 hour 30 minutes long . Each question is worth 15 marks .

 

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Your Q .

Structure of the exam .
Each paper is divided into two sections , Section A & Section B .

Section A of each paper has three-questions which are often divided into a number of parts ( a , c , & i ) ii) , iii ) & so on
with each part of the question relating to a different learning outcome , The number of marks available for each part of the question is shown on the paper & this can be used to indicate how long to spend on your answer .

Section B also has three questions, but these relate to the scenario contained within a " source " document . These questions may also be divided into parts but often relate to a single learning outcome . Candidates are expected to display an in-depth knowledge of the particular subject .

Note : 2394
►► Typical examples include ( DESCRIBING a TEST PROCRDURE ) or ( EVALUTING TEST RESULTS )

As the Chief Examiner , reminds us .

Knowledge of BS-7671
Guidance Note 3 &
Electricity at Work Regulations GS-38 is required by all candidates. Some candidates demonstrate little background knowledge and struggled with questions relating to the requirements of GS 38, the purpose of Initial Verification, the steps to take should a test fail and what the test button on an RCD does.

Chief Examiner (13) 2394: Chaps this is not a spin Off . from 2392/10 .. PS no written Exams .

The Chief Examiner is asking you . TO
Read carefully & answer what the ( Question actually Asks )

Often a question is answered ( INCORRECTLY ) because of a ( failure to UNDERSTAND ) what is being asked & what is required , it is an easy trap to fall into under exams conditions where you are under pressure .

Chief Examiner Report . is for a reason . Learn by our mistakes'

The danger here is that you may answer a question to which you know the answer , ( But ) which is not the question you have been asked in the paper ( 49% ) Remember , the questions are set to ( Establish your level of understanding in specific areas ) so the correct response is important if the marks are to be obtained ,

Chief Examiner Report . Learn by our mistakes'
Take a little longer to READ the QUESTION carefully to ensure you are quite clear about what is required .

 

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Where am I going Wrong !!

Chief Examiner : 2394 : Wording of Questions :

I will not download this again , ◄► Take heed

Coupled with the number o marks available . gives valuable clues as to what is expected , the words used in the question provide the first clue . if you look out for the following words & phrases & understand what they mean , you should be able to provide an appropriate answer .

Meanings : C&Gs

State :
The means the answer is expected to be a short statement , not a long or ( RAMBLING PARAGRAPH ) The response to this type of question may even be just a single word or group of words which may not be need to be a complete sentence .

List :
This means you should produce a simple list of items or actions , The answer should be similar to that produced for the " State " question , however ,
on this occasion the items would be expected to follow a sequence & form a list , as would be expected for a shopping trip .

Explain briefly :
This requires a brief explanation ; usually no more that one or two sentences . it does not require paragraphs of explanation & the word " briefly " is used to indicate this requirement .

Explain with the aid of a diagram :
This means exactly what is says . The answer should comprise both a diagram & an explanation , The examiner is trying to help you achieve maximum marks by asking for both an explanation & a diagram because this method of providing information is likely to be the most efficient .

Show all calculations :
Again the examiner is tying to help you score as many marks as possible, Where a calculation is required & the only thing offered by the candidate is the numerical answer , then if it is wrong , the candidate would score no marks . if the candidate includes each step of the calculation then marks will be awarded for each correct step . it is always in your best interest to show all stages of the process , Where relevant remember to show the applicable units which apply to your answer e.g. ( V , Ω , kA ) etc .

With the aid of a fully labelled diagram :
This indicates that a diagram needs to be provided with the component parts clearly labelled , The marks for these questions are divided between the diagram & the labelling .

To obtain the maximum marks for the question both the labelling & the diagram must be completed

Describe :
These questions often relate to test procedures & you are required to demonstrate your knowledge of the test process , look at the number of marks available to give you an indication of how much detail you need to go into .

Describe , in detail :
This indicates that a more detailed answer is required & again the number of marks available for the question gives an indication of the depth of the answer required

A series of short bullet pointed statements is a very effective method of providing an answer , but remember that all necessary information must be included

Direct measurement :
This indicates that a test is required & the results are not to be established by using a calculation . For example , where you are asked to describe the direct measurement of earth-fault-loop-impedance , ◄► Take heed
then a description of the test procedure is required , Describing an ( R[SUP]1[/SUP] + R[SUP]2[/SUP] ) test & then stating how to determine the value by calculation using , Zs = Ze + ( R[SUP]1[/SUP] + R[SUP]2[/SUP] ) will result in no marks being awarded for the answer .

 

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Terminology : ( When things go Pear Shape )

The simplest of mistakes will cost you . " marks "

it is important to answer questions using the correct terminology , which is the same as that used in GN-3 & BS-7671:2011:

Chief Examiner has given you a reasonable explanation . ( Why ) Always use correct titles & terminology .
Brand names should ( Not ) be used to describe items of equipment . test instruments & the like .

Chief Examiner , example
the instrument used to test for continuity is a low résistance ohmmeter . it should not be referred to using a manufactures name ( Megger ) or referred to as a continuity tester .

This is because the precise performance requirements given in BS-7671: & GN-3 must be Met . ◄◄

Some continuity testers & instruments that provide continuity features may not meet these requirements.

Your Q . ▼ Here's you reason .
Multifunction test instruments are commonly used for testing electrical installations . You need to be aware of the individual functions & ranges of these instruments , This includes such functions as insulation résistance , continuity , earth fault loop impedance & prospective fault current measurement .

The appropriate measurement scale for a particular test must be clearly stated , Also be careful to use the correct units & symbols to describe test instrument readings , ( mΩ , Ω , MΩ , A , kA , mS )

The use of the correct terminology for the component parts of an electrical system is also important .
The application of the terms used in BS-7671: is necessary as this leaves no doubt as to the part being described . typical terms , includes earthing-condutor , main-protective-bonding-conductors & circuit-protective-conductors , Terms such as ( earth wires or cross-bonding ) do not correctly identify components & the examiner is unable to award marks for such items .

Another common error is the use of incorrect titles for documents , if you refer to the " Electricity at Work Act " instead of the " Electricity at Work Regulations " or the Health & Safety at Work Regulation's instead of the " Health & Safety at Work Act " this will result in no marks being awarded. this also applies to the title of documents which are completed during the inspection & testing process & handed to the client .

 

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Section ( B )
Each paper is related to a scenario which is given in the Source Document .

The scenario gives details of an electrical installation , or part of an installation . it identifies what is to be carried out , & provides information that is to be used to answer the final three questions on the exam paper . This means that the answer to these questions should relate to the installation indentified in the scenario .

The most common error made by candidates at this point in the paper is failing to ( READ ) the scenario & apply the information given to these final three questions .

scenario , clearly states a TN-C-S system is used & a question asks for a diagram of the earth fault loop path , producing a drawing of a TN-S system will result in no marks being awarded . Etc

Common errors : when answering questions that relate to the scenario .
- not obtaining permission for isolation or for testing to proceed .
- no isolation procedure mentioned when it is appropriate
- no instrument & lead check carried out
- incorrect procedures described , such as not being able to describe the three steps in GN-3 for ring final circuit continuity
- not describing the test process in the correct sequence
- failure to consider the safety aspects necessary for the testing process
- failure to reinstate the installation safely once testing is complete

You are expected to be able to describe the procedures for carrying out activities , including the inspection & testing of installations & circuits , These descriptions should follow the format given in GN-3 .

 

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Written Examination 2395 . Q/As ( 1 )

(i) The electrical installation in a craft workshop is scheduled for a periodic inspection & test for insurance purposes .
a) State two statutory documents which apply to the inspection & testing process

A) Electricity at Work Regulations .
A) Health & Safety at Work ( etc ) Act .

Comments .
Abbreviations such as EWR & HSWA are acceptable . candidates must correctly identify whether these are an Act or Regulations in order to achieve the marks .

1 b) State three non-statutory documents which the inspector may need to refer to relating specifically to inspection & testing

BS-7671:
On - Site Guide
Guidance Note

Comments
GS-38 is an acceptable alternative so any three from these four are acceptable . Abbreviations such as OSG. & GN-3 are also acceptable answers . As the question asks for three items , the examiner will only mark the first three responses .

1 c) State who the inspector will consult to establish the extent & limitations of the periodic inspection & test
A) The client
A) The insurance company
Comments The person ordering the work or the person requesting the work are acceptable alternatives to the client . note Read the question carefully , the main question stem specifies that the work is for insurance purposes.

The response must relate to the insurance company & so other interested third parties or any other specific third party such as licensing authority etc will not receive a mark .

1 d ) Explain why the sequence of testing for the periodic inspection may be diffident to that given in BS-7671: for initial verification
A ) The installation has been inspected & tested & placed in service . Periodic inspection verifies the current condition or the safety of the installation 7 not the confirmation of the safety of the installation before placing in service

Comments
The candidate needs to explain the purpose of periodic inspection & how this differs from initial verification in order to obtain the marks, Examiners will consider the description used & whether this explains the reason for there being no sequence for the periodic tests . Answers such as inconvenience & because the installation is energised are not acceptable as these do not affect the sequence of testing but relate to the extent & limitations agreed with the client .

Tip . Many candidates confuse the sequence of tests with the sampling of the installation , sampling does not relate to the sequence , BS-7671: gives a required sequence of tests to be carried out at initial verification , All these tests could be carried out at periodic inspection but not necessarily in the same sequence . The answer needs to clarify why this is the case .

Chief Examiner had a field day with this ONE .

1 e ) State the first action to be taken by the inspector should an exposed live part be identified on a socket outlet circuit during the inspection
A ) Make a recommendation to the responsible person that the circuit is isolated until a repair can be carried out .

Comments
A ) Alternative answers include ;
inform client & obtain permission to isolate until repair can be carried out
Or
Isolate with the clients permission until a repair can be carried out .

Notes :
Isolate the supply & record the results , & similar answers are not acceptable as the inspector is required to inform 7 recommend the isolation . Not to carry out the isolation without first seeking agreement from the Client / User .

Guidance Note 3 , in the general requirements section , identifies the action to be " recommend the immediate isolation of the defective part "
The person ordering the work should be informed , in writing , of this recommendation without delay ,

 

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2 a ) A periodic inspection is to be taken in a hotel fitness room .
i) State three checks that need to be carried out to avoid damage to equipment before an insulation résistance test is conducted .

Comments :
Alternative answers include ; ensure no connection between live conductors & earth or link out controls .

As the question asks for three items , the examiner will only mark the first three responses .

2 a) ii) State the test voltages to be applied for the insulation résistance test

A) 500V
2 a) iii ) State the effects on the value of insulation résistance produced by cable length .

A ) As length increases resistance decreases

Comments :
An alternative answer includes as length decreases résistance increases .
Alternative terms such as higher or lower are acceptable

2 b) Insulation résistance tests between live conductors & earth on the individual circuits produced the following results , 200MΩ , 200MΩ , 150MΩ , 50MΩ , 25MΩ , 100MΩ , 2MΩ .

Calculate the expected overall value of insulation résistance if the installation was tested with ( with all the circuit connected )

Show all calculations .
A)

1/Rt = 1/R1 + 1/R2 + 1/R3 + 1/R4 + 1/R5 + 1/R6 + 1/R7

1/RT = 1/200 + 1/200 + 1/150 + 1/50 + 1/25 + 1/100 + 1/2

1/RT = 0.005 + 0.005 + 0.007 + 0.02 + 0.04 + 0.01 + 0.5

1/RT = 0.587

RT = 1.7MΩ

Comments :
Either the formula or the figures are acceptable for the first line . The correct units must be included in the final answer to obtain the marks .

Tip : it is important to show all the calculations' used to arrive at the answer as should an error be made the marks lost will relate just to the error whereas providing just the answer or omitting some calculation stages together with obtaining the wrong answer will result in all the marks being lost .

2 b ) ii) State , given reasons , whether the insulation résistance for the installation complies with BS-7671:
A ) 1.7MΩ ≥ than minimum 1MΩ & so it complies .

Comments :
Candidates need to explain the reason for their answer so simply " yes " would only receive 1 mark .

The response to Part (ii) of this question is dependent on the answer to the candidates response to Part (i) if the candidate has an incorrect answer in (i) this will not affect the marks awarded in (ii) The examiner will mark (ii) based upon the answer given by the candidate in (i)

 

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2394 : Inspection & Testing : Q/As . your turn , your call .

A test of continuity of the ring final circuit supplying the stages area socket-outlets is to be carried out .

i) State the test instrument to be used for the test .
ii) State ONE check to be made on the test instrument before carrying out the test other than calibration
iii) State the action to be taken with the test leads before the test is carried out . Remember this one .

 

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Inspection & Testing : Q/As .

C&Gs has put you on the Spot Here . You have to deal with it .

Q ) Describe how the continuity of ring final circuit test is to be carried out on Circuit 9 once the circuit has been safely isolated & secured ( 9 mark )
Q) State whether the earthing conductor is either connected or disconnected when carrying out tests to establish the prospective fault current .
Q ) Describe how a test is carried out to determine the prospective fault current at the origin of the installation by direct measurement ( 10 mark )
Q ) Explain how the inspector confirms that the installation complies with the requirements for prospective fault current protection

 

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Q ) Describe how the continuity of ring final circuit test is to be carried out on Circuit 9 once the circuit has been safely isolated & secured
A) Connected .
Comments .
As the Q asks whether the earthing conductor is connected or disconnected a single word answer is all that is necessary .

Q) State whether the earthing conductor is either connected or disconnected when carrying out tests to establish the prospective fault current
A)
- Secure the area around distribution board
- Access incoming live terminals
- Using a PFC tester ( or EFLI tester set to kA )
- Confirm test leads comply with GS-38
- Connect to incoming supply side Line and Earth
- Measure PSCC
- Record highest result as the PFC
- Reinstate the D/B .. Distribution board

Comments
in this case there have been no previous questions relating to the preparation such as type of instrument etc . and so this information needs to be included in the answer .

Failure to identify that the test leads must comply with GS-38 will lose seveal marks , it is vital to remember that the earthing and all protective bonding conductors are connected whilst this test is carried out .

 

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Mistake sorry about that . Windows 8 ▲▲▲▲ Discard Q/As .......................... ▲▲▲▲ Start again


Q ) Describe how a test is carried out to determine the prospective fault current at the origin of the installation by direct measurement

A)
- Secure the area around distribution board
- Access incoming live terminals
- Using a PFC tester ( or EFLI tester set to kA )
- Confirm test leads comply with GS-38
- Connect to incoming supply side Line and Earth
- Measure PSCC
- Record highest result as the PFC
- Reinstate the D/B .. Distribution board

Comments
in this case there have been no previous questions relating to the preparation such as type of instrument etc . and so this information needs to be included in the answer .

Failure to identify that the test leads must comply with GS-38 will lose several marks , it is vital to remember that the earthing and all protective bonding conductors are connected whilst this test is carried out .

 

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Q) State whether the earthing conductor is either connected or disconnected when carrying out tests to establish the prospective fault current .

A) Connected

Comments
As the Q asks whether the earthing conductor is connected or disconnected a single word answer is all that is necessary .

 

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GN-3 . P/54 . Instrument , Use the prospective fault current range of a suitable earth fault loop impedance tester for this test . 4.5 final paragraph

Using a PFC tester ( or EFLI tester set to kA )

GN-3 . Earth Fault Loop Impedance testers ; BS-EN-61557-3 .. Younger members

2394 : Q to A , These instrument operate by circulating a current from the Line-conductor into the protective earth . This will raise the potential of the protective earth system .

Q ) To minimise electric shock hazard from the potential of the protective conductor , the test duration should be within safe limits ????
PS , what is your safe limits .. C&Gs

4.5 Earth fault loop impedance
A) This means that the instrument should cut off the test current after 40mS .. refer to

 

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Q ) Explain how the inspector confirms that the installation complies with the requirements for prospective fault current protection

A) Confirm measured PFC is no greater than the breaking capacity ( or Icn ) of the protective devices

Comments
An alternative response would be : Protective device ( Icn ) is equal to or more than the measured PFC

GN-3 : P56 . The difference between the two short-circuit rating . refer to .

( Icn ) is the maximum fault current the device can interrupt safety without loss of performance .

for domestic installations the ( PFC ) is unlikely to exceed 6kA , up to which value ( Icn will equal Ics ) refer to .

 

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2395: Section B .

Remember that the answers to the following Q must relate to the scenario contained in the source document

4 a) Describe three actions the inspector can take to ensure that no danger occurs to those persons using the premises during the inspection & test .

A) inform people of the activities , use of barriers to secure work areas , use of warning signs .

Comments
Other answers could include safe isolation , avoidance of tripping hazards , not leaving covers open when unattended and so on , So any three suitable responses will be awarded marks . The responses should relate to avoiding danger to the user of the installation during the inspection & testing process . Working out of hours or when the hall is empty are not acceptable as the Q relates to the ( USERs ) whilst they are in the premises .

The examiner will mark only the first three answers provided as the question specifies three actions .

4 b) State the documents to be completed by the inspector and given to the client on completion of the inspection and test .
A) Electrical Installation Condition Report or ( EICR ) , Schedule of inspections , Schedule of Test Results .

Comments
These are the requirements identified in BS-7671: Titles used on the Standard Forms such as generic schedule of test results & Condition Report Inspection Schedule would also be accepted , Schedule of Test , Schedule of items tested etc will not attract marks .

4 c) An inspection is being carried out within the distribution board .
i) State three areas relating to the circuit breakers that are to be inspected .

A) Rating , Type , Short-circuit capacity

Comments
Other answers such as terminations , thermal damage would also be acceptable , The answers must relate to the circuit breakers & be inspection items not functional checks , Any three suitable answers will attract marks .

The examiner will mark the first three answers provided as the question specifies three areas .

4 c) ii) State what is being looked for by the inspector for each item in (i) above .

A) Correct circuit breaker rating , the correct type ( B , C , D ) is installed , the short-circuit rating is higher than the ( Ipƒ )

( Ipƒ ) prospective fault current . by Definitions' R/P.38

Comments
The answers given here must relate to the areas indentified in ( 4 c ) (i) and be in the same sequence to achieve the marks

The examiner will mark only the first three answers provided as the question specifies three areas .

4 c ) iii) State the human sense that will be used during each check in (ii) above .

A) Sight , Sight , Sight .

Comments
in this example all the checks would be carried out using the same sense and so an answer starting all three by sense of sight would be acceptable . if the terminations were used then touch would be appropriate and so no .

The examiner will mark only the first three answers provided as the question specifies three areas .

State the human sense that will be used , its here to stay . 2392 , 2394 , 2395 .

recap : R/P.29 . in the eyes of BS-7671:2011: Inspection .
Examination of an electrical installation using all the senses as appropriate .

 

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Level 3 Certificate in Initial Verification & Certification of Electrical Installation 2394-01 .
Quotes : taken .

C&Gs does not state formal candidate entry requirements .
The qualification is not intended for non-qualified electricians' and / or those who do not have experience in inspecting , testing & certifying electrical installations .

The Chief Examiners’ Report has been reintroduced as a result of feedback from centres, to give them guidance in preparing candidates for the written examination.

2394 : Many candidates were unable to state what was meant by the BS-EN-60898 circuit breaker ratings of ( Icn & Ics )

Testing
A number of candidates incorrectly stated that the earthing and bonding conductors are disconnected before carrying out a test of Prospective Fault Current (PFC).

A number of candidates failed to identify that the test for PFC was undertaken at the supply side of the main isolator.

When describing live tests many candidates did not state the need to confirm that the test leads complied with GS-38

Level 3 Certificate in the Periodic Inspection Testing & Certification of Electrical Installation 2395-01 .
Quotes : taken .

This qualification is intended for Experience people working in the electrical industry . Etc

2395 is one of the hardest Exams to undertake . it's not a walk-in the Park .

 

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2395 :

2 c ) The lighting comprises a number of discharge luminaires .
State the alternative methods of preparing this circuit for the insulation résistance test .

A) Disconnect all luminaires or link live conductors and then test live conductors to Earth .

C ;
An alternative answer for one of these is to switch off at the local switch .

tip ; When testing insulation résistance the measurements must be taken to Earth & disconnecting & testing to a CPC will result in marks being lost .

3 a ) (i) Explain the cause of voltage drop within an installation .

A) Volt drop is a product of the conductor résistance and the load current .

C ;
The question refers to the volt drop that occurs normally within the installation which is caused by the conductor résistance and the current flowing . Do not confuse this with the causes of excess voltage drop due to poor design or overloading of the circuit .

3 a ) (ii) State the two methods of determining voltage drop .

A) Measurement & Calculation .

C ;
it is not acceptable to carry out a direct measurement of voltage drop using volt-meter(s) The circuit conductors must be at their normal operating temperature , the circuit under full-load and there must be no variation in the supply voltage during the test , the methods given are as a result of the measurement of conductor résistance and the reference to charts or tables giving the details of voltage drop , these are not the figures in the tables in Appendix 4 of BS-7671: which are generic design details for the calculation of appropriate cable sizes .

3 b ) (i) A radial circuit has a load current ( Ib ) of 28A at 230V a.c. and has a combined live conductor résistance of ( 0.16Ω ) at ( 20ºC ) Determine the voltage drop for this circuit , Show all calculations ◄

A) Voltage drop = ( R[SUP]1[/SUP] + R[SUP] N[/SUP] ) x Ib x 1.2 .. so voltage drop = 0.16 x 28 x 1.2 = 5.376V

C ;
The use of the conductor résistance and load current together with the ( 1.2 multiplier ) to compensate for the difference in conductor temperature at the time of test and the normal operating temperature of the conductors when maximum résistance and hence maximum volt drop will occur .

3 b) (ii) if the radial circuit supplies a machine lathe , determine whether the voltage drop in (b) i) above complies with BS-7671:

A) Maximum volt drop = 230V x 5% = 11.5V ... As 5.376V is equal to or less than 11.5V so complies

C ;
Alternative calculations such as : maximum volt drop = 5% drop = 5.376 / 230 x 100 = 2.3% which is less than 5%
may be used & will attract the same marks .

Tip . it is important to show the calculations because in this type of question where an error is made in the calculation candidates are only penalised once for the error . the remainder of the answer is marked based upon the incorrect figure produced and , providing the process is correct , marled accordingly , candidate could have completely the wrong answer for ( 3 b i ) but based upon their incorrect figure from that calculation achieve full marks for ( 3 b ii ) providing their calculation and conclusion is correct .

 

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Q/As 2394:
in order to undertake the inspection & testing of an electrical installation a person must be a ;
Competent person
Principle person
Duty person
Registered person

.. take your best shot . R/P/389 under the heading of (i) (ii) (iii) . Competent persons will , as appropriate to their functions

Regulation 16 of the Electricity at Work Regulations requires persons to be competent to prevent danger .
As such danger can occur when carrying out an inspection & test on an electrical installation , the inspector is required to be competent , this is further reinforced in GN-3 as certification & reports are required to be signed by a competent person .

 

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Q/As
The term " Dutyholder " used in the Electricity at Work Regulations refers to the person :
making the final payment on completion of the work
responsible for the electrical installation
reviewing the documents
ordering the work

Electricity at Work Regulations identifies anyone taking control of , or responsibility for , an electrical system as a Dutyholder ( Memorandum of Guidance Regulation 3 item 55 ) Dutyholder.s have a duty to ensure the safety of themselves and others .

 

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Q/As 2394:
Which of the following identifies the correct process for safe isolation of a circuit protected by a circuit breaker

Switch off , post notices
Switch off , lock off , post notices
Switch off , confirm isolation , post notices
Switch off , lock off , confirm isolation , post notices

All of the steps listed in option are required to complete isolation and to ensure the circuit is safe to work on .

 

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Q/As 2394:

Work is to be carried out on an installation which includes a Solar ( PV supply system ) Which of the following must be carried out before isolating the ( DNO ) supply to the installation

Isolate the Solar PV supply .
Disconnect the installation loads .
Closes all the switches .
Disconnect the bonding conductors .

Solar PV system's generate even at low light levels and to ensure the safety of the inspector and those persons in the vicinity the system must be isolated .
Solar PV system's are an alternative source of supply . Although many Solar PV system's will shut down automatically following loss of supply . this should never be taken for granted and isolation of the PV system should always be carried out .

 

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Q/As 2394:

A test of earth fault loop impedance is to be carried out in an area which is accessible to the public , Which of the following is not a suitable method of protecting the public from the risk of electric shock . .. PS the word is NOT

Barriers .
Warning signs .
Safe isolation .
Restricting access .

Safe isolation is not appropriate in this instance as the test is a live test and so has to be carried out with the supply connected .

 

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Q/As

Work is to be carried out at the distribution board supplying a multi-storey office building , which of the following must be placed out of service , to ensure the safety of the users , before the safe isolation of the distribution board is carried out .

General lighting circuits.
Air conditioning system .
Lifts to all floors .
Burglar alarms .

The client's agreement to isolate the lift supplies must be obtained and the lift's taken out of service to prevent persons being trapped in the lifts when the supply to the distribution board is isolated .

 

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Q/As 2394 .
Who is most at risk when an Inspector fails to isolate a lighting circuit before removing a luminaire cover to carry out an inspection .

The inspector .
Other operatives .
The general public .
The client .

As the work is being carried out by the inspector and the other persons listed are unlikely to have access to the luminaire the inspector is at most risk when isolation is not carried out prior to dismantling .

 

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Q/As 2394 .

Which publication specifically identifies the need for electrical installations to be safe for use and maintained in that condition .

HSE Guidance GS-38
Electricity at Work Regulations
The Health & Safety at Work ( etc ) Act
Electricity Safety , Quality & Continuity Regulations .

Regulation 4 of the Electricity at Work Regulations requires electrical systems to be installed and maintained so far is reasonably practical to prevent danger .

 

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Q/As 2394 .

Which publication specifically indentifies the requirements for test leads & probes to be used when carrying out tests at 230V a.c.

BS-7671
HSE Guidance GS-38
Electricity at Work Regulations
Provision and Use of Work Equipment Regulations

HSE GS-38 provides guidance on the test equipment used for circuits with rated voltages not exceeding 650V

 

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Q/As 2394 .

Which test is used to confirm the correct connection of a three-phase socket-outlet .

Phase sequence .
Insulation résistance
Earth fault loop impedance .
Operation of residual current devices .

A three - phase socket-outlet should be confirmed as having correct Phase sequence to ensure the correct connection of any equipment plugged into it . The other test listed will confirm the compliance of the circuit .

 

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Q/As 2394 .

Which test is required to confirm the correct operation of a 30mA RCBO installed to provide additional protection .

Phase sequence .
Insulation résistance
Earth fault loop impedance .
Operation of residual current devices .

The operation of the RCD component of the RCBO must be tested to confirm correct operation , as required in GN-3 .