Re-take - Useful Information for 2394 :

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Gentle - reminder .
It would appear that candidates are notaware that a ( Working-knowledge of Guidance-Note - 3 . & BS-7671:2008:2011: ) is required to achieve success in thisqualification .

Gentle - reminder .
It would appear that candidates are notaware that a ( Working-knowledge of Guidance-Note - 3 . & BS-7671:2008:2011: ) is required to achieve success
in this qualification . candidatesdemonstrated gaps in both technical and underpinning of subject-matter .

Back to basics .
16[SUP]th[/SUP] Edition - BS-EN-61008-1 . 1995 . General-rules . ( ReplacesBS-4293 ) 1983 . which remains-current .
16[SUP]th[/SUP] Edition - BS-4293 : 1983 - ( 1993 )Specification for residual-current-operated-circuit-breakers . ( Replacedby BS-EN-61008-1 )

P.286 . BS-7671:2008:2011:
BS-EN-61008-1 . 2004 +12:2009 . residual-current-operated-circuit-breakers - ( without-integral-overcurrent-protection) for household and similar uses - ( RCCBs ) General-rules .

 

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C&G -2394 . and C&G - 2395 . splits the previous- 2391 down the middle .

2394: Initial-verification-qualification . Inspection& Testing . New-installation(s)
2395 : Periodic-inspection-qualification . Inspection & Testing . Existing-installation(s)

C&G - 2394. exam forms part of what was previously known as the 2391-10 . The qualificationhas been split into-two-routes .

Gentle - reminder .
It would appearthat candidates are not aware that a (Working-knowledge of Guidance-Note- 3 . & BS-7671:2008:2011: ) is required toachieve success in this qualification .

Appendix - 1 - Normative . p.277 . ( Where did I go wrong with . my Q/As . BS- .BS-EN ) RCDs
Note : CertainBritish-Standards . have been withdrawn since the issue of the - 16[SUP]th[/SUP] Edition in 2001 . from the dateof withdrawal . certificates and marks already awarded may continue to apply to. production until a date-specified in the - superseding-standard . Etc .

Characteristicsof RCDs . Basics .
RCDs aredefined by a series of electrical-characteristics. three-main-characteristics are :
i) . Therating of the device in amperes ( I )
ii) . The rated-residual-operating-current of the protective-device in - amperes . IΔn

iii) . Whether the device operates ??
- Instantaneously. - ( G )
- Incorporatesan . international-time-delay - 2394: To permit discrimination . (S )

p.26. Discrimination - Ability of a protective-device tooperate in preference to another . protective-device in series .

 

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Items : need to be addressed when providing-switchingoff for ( Mechanical-maintenance ) of an extractor-fan .

Purpose ofswitching off for - ( Mechanical-maintenance )
The purposeof switching off an ( Extractor-fan for Mechanical-maintenance) is to provide-protection for a person-engaged in carrying out . (Mechanical-maintenance ) that may otherwise involve the risk of physical-injury . such as burns . or injury from . ( Mechanical-movement ) such as from arotating-fan-blade . - Regulation /537.3.1.1. refer

Switching devicepositioning or marking :
eachdevice for switching of an - ( Extractor-fan for Mechanical-maintenance ) is tobe durably-marked . and located so as to be readily-identifiable and convenient. for the intended use . - Regulation / 537.3.2.4.

□ example of awall-mounted-extractor-fan-switching-device . note :- this device is notsuitable for - installation where unintentional-reactivation of equipment may occur . ▼

Unintentional-reactivationof equipment :
the meansfor switching off an extractor-fan for ( Mechanical-maintenance ) shouldpreferably be positioned where it will be . continuously under the control ofthe person-working of the fan . However , where this is not practicable .suitable-provision must be made so that precautions can be taken to prevent .any electrically-powered-equipment frombeing unintentionally-reactivated-during-the ( Mechanical-maintenance ) Regulation/ 537.3.1.2.
refer. such a provision is for the switch tobe provided with a device that . enables the extractor-fan-switching-device to be padlocked in the disconnected-position . with theswitching-device-locked-off and thekey-under-the control of the person-carrying out the ( Mechanical-maintenance ) inadvertent and unauthorized-operation of theswitching-device is prevented - Regulation / 537.3.1.2. refers .

Indicationof switching-position :
The Open-position of the contacts of a device for switching offfor . ( Mechanical-maintenance ) must be visible . or the OFF or OPEN-position must be clearly and reliably-indicated - Regulation /537.3.2.2. refers . Indication of that position must occur only when the (OFF or OPEN-position ) on each-pole hasbeen fully-attained . an indicator-light will not meet the requirements . forindication . positive - ( Mechanical-indication ) such as the position of anoperating-handle is required .

Switching ofan extractor fan with a - run-on-timer-connected toa lighting-circuit :
Control ofan extractor-fan with . run-on-timer-connected to a lighting-circuit . is often-provided for a toilet or bathroom . so that the fan-continues to run for a .predetermined-period after the light isswitched-OFF . in such an arrangement . the fan is functionally-operated by the ( Light-switch ) so as to allowthe automatic-fan-run-on-operation .

Fan-isolator-switch- ON / OFF indicator . pull-cord-type
Question 2394: does a Light-pull-cord show us indication . when OFF or ON. Question- is the lamp blown . ?? what indication do we have .

□ Fan-isolator-switch -Three-pole with padlock . surface-mounted .
□ 3 - pole-fan-isolator-ceiling-pull-cord-switch .

Has thebathroom got a window ??? . it is a 100% - requirement if there is No-Window .

( Fan-isolator-switch- ON / OFF indicator . pull-cord-type )
( Fan-isolator-switch - Three-pole with padlock . surface-mounted ) mustbe positioned outside of the room-containing-the-shower.

Example : Shower -extractor-fan . this has been specifically-designed for the use in a . shower and it also incorporates a halogen-lamp which is 12V .
Fans like this require-additional-wiring as both a . permanent-live . and switched-live . are required as the fan has a built-in-timer .so that it continues to extract-air fora set-period of time . after the light in the room has been switched-OFF .

These fans are wiredfrom the existing-light in theshower-area and go via a three-pole-switch to the fanitself . when you operate the shower-room-light the fan switches on automatically and switches OFF . after a set period-time .

( three-pole-switchto the fan itself ) allLive-conductors can be isolated . when needed .

- Switched-live : it becomes live when the switch is ON .
- Permanent-live : this is live all the time .

► Old-colours - Fan-isolator . 3-core & earth .
Switched live ( it becomes live whenthe switch is on ) “ Yellow “ L1 / SL ( Sleeved - Red )
Permanent live (this is live all the time) “ Red “ L2 / L
Neutral → Blue .

Harmonised-colours :
Switched live ( it becomes live when the switch is on ) “ Black “ L1 / SL
Permanent live (this is live all the time) “ Brown “ L2 / L
Neutral → Gray - sleeved Blue .

 

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2394 : we have to brushup on - Isolation . Yeah . for you exams

 

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Gentle - reminder . Chief-examiners-report - 2012 .
It would appear thatcandidates are not aware that a ( Working-knowledge of Guidance-note-3 . & BS-7671:2008:2011: ) is required to achieve success in this qualification . candidates demonstrated ( gaps) in both Technical and Underpinning of subject matters . Based




- - - Updated - - -

RCD -Testing :
Testingthe ( Trip - times of RCDs ) with all commonly found RCD - current-ratings .
For most -International-applications & the UK . 5 test(s) must be - performed .

1) - (1/2) x RCD - current-rating . to ensure theRCD does not trip when ( Half ) the rated-current is following in the RCD .
100% . 2) - 1 x RCD -current-rating . This is a trip-test to ensure the . RCD - trips with the specified-trip-time .
500% . 3) - 5 x RCD -current-rating . A trip-test to ensure theRCD - trips within the specified-time .
4 & 5) both the ( 1 x and 5 x tests ) must bepreformed at both - ( -&-s 0° degrees and 180° degrees . positive and negative-supply-half-cycles . to ensure ( Worst-case-time is recorded)

Theauto - RCD test : allows all the above tests to be preformed - Automaticallywhilst the operator . stands by the RCD and resets it as it Trips . results can then be recalled tothe screen .

 

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Functional-Testing- 612.13.1.
Whichstates that for an RCD ( Theeffectiveness of any test-facility incorporated in the device shall be Verified)

Re-cap :Built-in-test-button . RCDs
test-button- can be used to place a load between the output - Line-conductor and theinput-neutral-conductor . creating animbalance in the windings . this imbalance causes the RCD to trip .

point to note : thetest-button only demonstrates that the trip-mechanism-works . confirming-nothing-else .about it’s specific-operational- characteristics .

 

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Re-cap -2394: with 2008: & 2011:
17[SUP]th[/SUP]Edition increases the need for circuit(s) to be provided with RCD-protection -The circuit(s) that require RCD are as follows .

i) . Where the - Earth-fault-loop-impedance . isto high to provide the required-disconnection-times . where thedistributor - ( DNO ) or does notprovide an Earth - TT - system(s) 411.5.
ii) . Socket-outlet - circuit(s) in domestic andsimilar-installation(s) - 411.3.3.
iii) . For circuit(s) of locations-containing-a bathor shower - 701.411.3.3.
iv) . For circuit(s) supplying mobile-equipment .not exceeding - 32A for use outdoors - 411.3.3.
v) . For cables without earthed-metallic-coveringinstalled in walls or partitions at a depth of less than 50mm and not protectedby earthed-steel-conduit or similar - 522.6.7.
vi) . Forcables without earthed-metallic-covering installed in walls or partitions withmetal-parts - excluding screws or nails . and not protected byearthed-steel-conduct or the like - 522.6.8.

for items( ii and vi ) above the RCDs used shouldbe rated at 30mA .

 

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(Additional-Protection Only ) 5 x 30 =150mA
RCDs are rated at . 30mA and 40mS . andmust disconnect the supply within ( 40mS ) for a leakage-current of ( 5 x times) the rated-operating-current - 150mA . refer to BS-7671:2008:2011: - 415.1.1.

 

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Useful- junk ( 5x and x5 ) are the same thing . RCDs

 

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Re-cap . What the Regulations arereminding us . p.29 / p.36 .

□ Inspection :-Examination of an electrical-installation using all the ( Senses as appropriate )

□ Testing :- Implementation of ( measures to assess ) an electrical-installation by means of which its . ( effectiveness is proved ) this includesascertaining-values by means of ( appropriate-measuring-instrument(s) ◄ it has been -Defined . Part - 4 . 2 . 3 . 5 . 6 . refer to . GN-3 .

□ Verification :- All ( measures by means ) ofwhich compliance of the electrical-installation with the relevant-requirementsof - BS-7671 : are checked . comprising . Inspection . Testing and Certification .

 

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BS-7671:2011: BS-EN-61557 : P.288 .
BS-EN-61557: Electrical-safety in low voltage distribution systems up to 1000V a.c and 1500V d.c. - Equipment for testing . measuring ormonitoring of protective-measures . ( General-requirements ) 612.1. - 621.3.

P.190 - BS-7671:2011: 612.1.

Testing :
The tests of . Regulations - 612.2. to 13 . where relevant . shall becarried out and the results compared with relevant-criteria .

P.194 - 621.3.
Periodic-inspectionand Testing :
Precautionsshall be taken to ( Ensure ) that the periodic-inspection and testing shall not cause ( Danger ) to persons or livestock . and shall not cause damage to property and equipment even if the circuit is defective . Measuring-instrumentsand monitoring-equipment and methods shall be chosen in accordance withrelevant-parts of ( BS-EN-61557 ) ifother measuring-equipmentis used . it shall provide no less degree ofperformance and safety .

BS-EN-61557-2 :Insulation-résistance .

p.288 . BS-EN-61557-6 : 1998 .Residual-current-devices - ( RCD ) in TT . TN - 612.8.1 . a) 2)
p.193 : General .
The - Verification . ofthe effectiveness of the measures for . fault-protection byautomatic-disconnection of supply is effected as follows . a) 2)
a) TN - system . Compliance with .Regulation - 411.4. shall be verified by . (2)
verification of the -characteristics and / or effectiveness of the associated-protective-device .This verification shall be made :

- for -Overcurrent-protective-devices . by ( Visual-inspection ) i.e. short-time or instantaneous-trippingsettings for circuit-breakers . current-rated and type for fuses .
- for - RCDs . by ( Visual-inspection & Test ◄ ) The effectiveness of disconnection ofsupply by RCDs . shall be verified using ( Suitable-test-equipment according to BS-EN-61557-6 . ( Part - 6 ) Regulation - 612.1. to confirm that therelevant-requirements in . Chapter - 41 are met .

Testing :
The tests of . Regulations - 612.1. where relevant . shall be carried outand the results compared with relevant-criteria .

The disconnection-timesrequired by . Chapter - 41 shall be verified . → Chapter - 41 . Protection againstelectric-shock .

Safety -LVD .

BS-EN-61557: Electrical-safety in low voltage distribution systems up to 1000V a.c and 1500V d.c. - Equipment for testing . measuring ormonitoring of protective-measures . ( General-requirements )

Part - 1 :General-requirements .
Part - 2 : Insulation-résistance-testers .
Part - 3 : Loop-résistance .
Part - 4 : Low-résistance-ohmmeters .
Part - 6 : Residual-current-devices - RCDs . in TT and TN- system(s)
Part - 7Phase-sequence .

Other reference standards for testing - RCDs .
RCD -Standards : BS-EN-61008-1 . BS-EN-61009-1

BS-EN-61008-1 : ( Part - 1 )
Residual-current-operated-circuit-breaker - ( Without ) integral-overcurrent-protection . for household andsimilar uses. ( General-rules )
BS-EN-61009-1 : ( Part - 1 )
Residual-current-operated-circuit-breaker - ( With ) integral-overcurrent-protection . for household andsimilar uses. ( General-rules )

Current-multiplier ( x ) x 1 / 100%.
Current-multiplier ( x ) x 5 / 500%.

Megger -1552 . Do we get lazy withMultifunctional instrument(s) .
Two-settings.
Automatic: - Nulling-out . “ Leads “
Manual : By calculation . Subtracting . “ Leads “

RCD - ( G ) ~ 30mA . ( BS-EN ) ◄

For thesake off . -&-s . Select the -RCD-function using thefunction-selector-switch . Am using theword - Manual - Setting(s) : back to basics

( 1/2 . 0.5 ) Half of 30mA / 15mA .
- Start ofTest : with ( IΔn ) 0° .step 1 . RCD should not Trip .
- Start ofTest : with ( IΔn ) 180° .step 2 . RCD should not Trip .

(500% . x5 )
- Start ofTest : with ( 5 x IΔn ) 0° .step 3 . RCD should Trip-out . ( Example - 0° / 7.7mS … 180° / 11.1mS ) Manual .
Re-activateRCD . - Start of Test : with ( 5 x IΔn ) 180° .step 4 . RCD should Trip-out .

(100% . x1 )
- Start ofTest : with ( 1 x IΔn ) 0° .step 5 . RCD should Trip-out . ( Example - 0° / 46.0mS … 180° / 35.7mS ) Manual .
Re-activateRCD . - Start of Test : with ( 1 x IΔn ) 180° .step 6 . RCD should Trip-out .

Highest → of the two-readingsshould be recorded - Certificate

 

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Re-cap. Table- 3A / p.295 . BS-EN-61008-1 : & BS-EN-61009-1 :
Delay ( S ) Trip-time (mS ) Minimum & Maximum . tΔ .. 130mS < tΔ < 500mS .

Table -41.5 gives maximum-values of ( Zs ) for non-time-delayed - RCDs .

 

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Value ofthe two-current-tests ??? ( Example - 0° ~ / 46.0mS … 180° ~ / 35.7mS )

 

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Re-cap :2394 . ( Additional-protection - 30mA only ) 5x .

 

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2394: Guessworkdoes not pay .

Point to Note : it appears thatmany candidates believe the . Minimum-acceptable-value forinsulation-résistance is ( 2MΩ and not1MΩ ) stated in BS-7671:2008:2011:

Re-cap. Table - 61 . MINIMUM-value of insulation-résistance . Wording is MINIMUM . ( 1MΩ ) BS-7671:2008:2011:
Note - 2: Insulation-résistance-value(s) are usually-higher than those of Table-61 . ◄◄◄◄◄

 

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Point toNote : - Exams 2394 : There is no excuse for studying for any exams. Q/As are taken from . BS-7671:2008:2011: - GN-3 .

Point to Note : “ a Must “ GN-3 . P.58 . :mad2:
Operationof residual-current-devices . ← ← ← ← ← ← .
411.4.5. - For each of the tests . readings should betaken on ( Both-positive and negative-half-cycles ) ↔ ( 0° & 180° ) andthe longer-operating-time-recorded .

Technical-Knowledge; Examiners - 2012 .

Many-candidateswere unable to correctly -indentify the requirements for the application ofRCDs . the Maximum-test-currents appliedand the Maximum-operating-times . many candidates failed to score as well asthey may as they failed to indentify the test-currents . in mA . to be appliedat each step of the test . failed to indentify the correct-operating-times ateach step and not indentifying that the ( Highest of the values at 0° and 180° ) should be recorded . Many candidatesfailed to confirm the operation of the ( Test-button ) on completion of the electrical-tests. Somecandidates stated incorrectly that an RCD to - BS-EN-61008-1 should disconnectin ( 200mS ) whentested at 5 x IΔn .

 

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Regulationshave to state the facts : p.167

Facts : Minimum-cross-sectional-area of the . main-protective-bonding-conductor .in relation to the ( Neutral of the supply )

Electrical-installation-condition-reports. & “ Testing “

Gas &Water-installation-pipe(s) The size of main-protective-bonding-conductor is always selectedfor the appropriate tables in the regulations . 54.8.
( 10.0mm[SUP]2[/SUP] ) is fine for most installations of a C.S.A.of the supply-neutral-conductor ( table- 54.8. - 35mm[SUP]2[/SUP] or less 10.0mm[SUP]2[/SUP] )

The conductorsare connected in a appropriate-place forboth the Gas - Water-installation-pipe(s) using BS-951 - clamps . and also suitable indentifiedwith the correct-label . - Provision of earthing and bonding-labels at all appropriate-locations

Older-installation(s) where the installation has - supplementary-bonding they will also have to bechecked . - Provision of earthing and bonding-labels at allappropriate-locations

 

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Verifying( Zs ) readings . ( Lighting-circuit )
Determine ( Zs ) adding ( Ze ) which you determined during the prospective-earth-fault-current-test. to your value of ( R[SUP]1[/SUP] + R[SUP]2[/SUP] ) looking attable - 41.3. Maximum - ( Zs is 6A - 7.67Ω ) for a 6A circuit-breaker to operate . your ( Zs ) is well below this . it is important to remember that theregulations do require a adjustment to the figure to allow for the increase ofrésistance of conductors of increase oftemperature when a circuit is under-load .

You canfind guidance on this - Appendix - 14 . p.424. 80% method . so the tabulated - (Zs ) needs to be reduced to 80% - per-cent of its value you can just do this multiplying . ( 7.67 x 0.8 = 6.14Ω )

 

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Used as a Leaning-curve .

High-current-loop-testing :
For Supplies that are ( Not RCD - protected ) thehigh-current-test . can be used . as there is no-risk of tripping and RCD .

Megger - LTW-325 : Loop-impedance-tester .
Two-wires -loop-impedance-measurement

Line to earth - testing.
Line toneutral - testing .
Prospective-short-circuit-current-test. ( PSCC )

The ideaof this test is to measure the maximum-current that can flow betweenlive-conductor(s) in the event of a fault .
The reasonthat we have to know this to make sure that we select the right type ofprotective-device . where it is installed in the circuit .it needs to carry thehighest amount of current without damage . Megger - LTW-325 . Loop / No-trip . Loop / Max-Z

Firstly :we must have Safe-Isolation . locking - OFF . Padlock
Danger -400 Volts .
Warning -This is a Live-test .

Green-lead- onto the neutral .
Loop / Max - Z. Loop - high-current .
Testbetween the neutral which is a live-conductor - then test between the incoming- line-conductor . PFC - ( 2241A ) which is 2.24kA .
Need to dothe same test between all three-line-conductors . ( L1 . L2 . L3 )

Brown - L1 - 2241kA . 2.24kA .
Black- L2 - 2256kA . 2.25kA
Gray - L3 - 2257kA . 2.25kA

We can seethat the reads 2.25kA .
becausethis is a Three-phase supply . you need to double the valve I’ve got . 2.25 x2 is 4.5 . ( 4.5kA is what you write onyour test - certificate )

Megger - LTW-325 : Loop-impedance-tester .
External-earth-loop-impedance-test- ( Ze ) Earth-fault-loop-impedance-test-instrument .

Firstly :We must have Safe-Isolation . locking - OFF . Padlock
Danger -400 Volts .
Warning -This is a Live-test .

Disconnectedthe - Earthing-conductor . ( Which is aProtective-conductor )
Reason forthis . We do not want ( Parallel - paths ) we need to know the résistance between hereand the supply-transformer .

With leadsto GS-38 .
Green-lead with a crocodile-clip .
Red - lead. with plastic-cover with maximum cover . 2mm . ( Live-parts )
Loop /High-current .
Loop / Max - Z.

Connectthe Green-lead with a crocodile-clip . To the disconnected - Earthing-conductor .
With theRed-lead . with plastic-cover with maximum cover . 2mm . ( Live-parts )

Brown - L1 - incoming Line to earth . value of 0.17Ω. you’ll need to know the highest-value . you’ll testbetween all three-lines .
Black- L2 - 0.17Ω
Gray - L3 - 0.17Ω . thereall consistent . so your value is - 0.17Ω .

 

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Ring-final-circuit-test.

Firstly :We must have Safe-Isolation . locking - OFF .
3 - thingsneeded . Lock-off that is appropriate forthe type off isolation . Padlock for locking-off . Sign - danger-do-not-switch-on.
Danger -400 Volts .
Warning -This is a Live-test .

Wheninsolating any-mains . ask permission . is it safe to do so .
Lock -off . placing the lock-off . padlock . cable-tie the Sign onto the padlock - danger-do-not-switch-on . You are the key-holder .

Is it Dead - With a approved-voltage-indicator
Test between. Earth to Line .
Testbetween . Earth and Neutral .
Testbetween . Neutral and Line .

With aknown device - proving-unit . With aapproved-voltage-indicator - all lightsare working .
Back to. With a approved-voltage-indicator . Test between . Earth and Line .

Ring-final-circuit-test- with all the cables disconnected .
Instrument-use. Low-résistance-ohm-meter . turn it on. and Null the leads . Re-cap . you leads have résistance 0.04Ω in them . which you do not want toinclude in your test . Zero the Leads .

Test each-conductor. End-to-end . ( Single-cables arethe same-size 2.5mm[SUP]2 [/SUP] ) not T&E .
Line-conductor(s) - 0.56Ω .
Neutral-conductor(s) - 0.55Ω
Circuit-protective-conductor(s) - 0.57Ω

Next :- Cross-connect the . Line and neutral-conductor - Connector-block .
Next :- Cross-connect the . Neutral and Line-conductor - Connector-block .

Dead /Testing . - your probes are 4mm . Not a Live-test . test between the two-ends off theconnector / blocks . ( Loop ) 0.27Ω you should be getting half the reading of one of these conductors . go toeach-socket-outlet . & test between each Line and Neutral at each socket .
You are .checking that it is a Ring. And no interconnections . from a socket-out-let - Line/ Neutral - 0.31Ω . ( Plus - Polarity) by continuity - method

You havecheck the . Line and Neutral at each-socket=outlet .
You doingthe same test . between the Line and Earth . & at each-socket-outlet .

Next :- Cross-connect the . Line(s) and Earth(s) - Connector-block . 0.27Ω . all you socket-outlets have beentested . your at the last-one - reading between .05Ω & the originalreading of 0.27Ω . - your reading is 0.29Ω