Re-take - Useful Information for 2394 :

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IEC-479-1 :

A residual-current-device . will ( Reduce ) the risk of Electric-shock .

Providedit has a residual-operating-current . not exceeding 30mA. & an operating-time not exceeding. 40mS . when a residual-current of 150mA - flows .
Thesecharacteristics are derived from the graph-shown . effects of current on thehuman-body can tolerate verysmall-currents for reasonably-long-periods . & moderate-currents forvery-short-periods .

Conductor(s): résistance .
Theease by which a . material-conducts electricity . is known as - résistance .

Conductor(s)- Interpreting .

Neutral-conductor. is defined as a . Live-conductor .
p.31: Neutral-conductor - A conductor connected to the . neutral-point of a system .& ( Contributing ) tothe transmission of ( Electrical-energy )

p.30: definition of - Live-conductor . refersto the . definition for . Live-parts .
Live-parts- a conductor or conductive-part intended to be . energized innormal-use . ( Including ) a neutral-conductor . Etc . This confirms that the . Line &Neutral-conductors . are both . Live-conductor(s) when energised .

(G ) RCD - device . as the earth-fault-current - ( If ) is . likely to be much higher than the . IΔn settings of the device installed . 30mA ÷ 1000 = 0.03A .

 

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2394:
Circuit-breakers. ( is both a Circuit-breaking-device ) Emergency / switching . Table - 53.4.

Overcurrents- are detected by . three-different-devices .
-Thermal for Overloads .
-Magnetic releases . which aregenerally-combined - ( Thermal / Magnetic-circuit-breakers )

2394: Very basics . BS-EN-60898 - Manual or Automatic-control - of acircuit .

Circuit-breakersare identified with . Two-breaking-capacities .

6kA )- . BS-EN-60898- standard for household or similar-applications. where Unqualified-persons. can re-closes a circuit with a persistent fault-several-times . the breaking-capacity - in Amps .
p.285 . BS-EN-60898- 1 .Specification for circuit-breakers for . Overcurrent-protection . for household & similar-installations.

p.286. BS-EN-60947-2 . Circuit-breakers 10kA . Qualified-persons .

p.149. Circuit-breakers : Table-53.4.
BS-EN-60898 .
BS-EN-60947-2.
BS-EN-61009-1.

Donot get mix up .

BS-EN-60947 . Low-voltage . switchgear & control-gear .

BS-EN-60947-2. Circuit-breakers - 2006 .

 

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Table- 41.2. : 41.4 : Type of fuses .
Fusesare indentified by . 2 - letters . according to their application-category . in ( LV-installation )

Thefirst-letter . indicates the . main-operation . ( g ) = general .
Thesecond-letter . indicates the . categoryof equipment to be protected .
G) protection of cables & conductors.
M) protection of . motor-circuits .
(gG ) - ( gM )

 

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DNO: It is noted that .Supply-cut-out-fuses . are allowed to be utilized for overload-protection . ofthe main-supply-cables - 433.3.1.


Note : we are using thecircuit-breaker-side BS-EN-61009-1 .
Note : Regulations - 41.3. BS-EN-60898 & BS-EN-61009-1 .
Maximum-earth-fault-loop-impedance. ( Zs ) for circuit-breakers with . Uoof 230V . for . ( Instantaneous-operation ) Etc .

Domestic-installationsthe . ( PFC ) is unlikely to exceed . 6kA . up to which value the . [ Icn ] & [ Ics ] valuesare the same .
PlainEnglish - Note . Two-rated-short-circuit-ratings. protective-devices . BS-EN-60898 & BS-EN-61009-1 .

GN-3: p.100 - reminds us . Generic Scheduleof Test Results .
3). BS ( EN ) enter the . standard of manufacture of the .circuit-protective-device . e.g.
4). Type - where relevant for . circuit-breakers enter the sensitivity type .e.g. - C . ( B . C. D . time-characteristics )
5). Rating - enter the .protective-device-current-rating .
6). Breaking-capacity - enter the . protective-device-breaking-capacity . often “printed on the circuit-breakers “ e.g. 6.

GN-3- p.56 . [ Icn ] & [ Ics ] Two-rated-short-circuit-ratings. table - 2.8. [ Icn - 6 ] & [ Ics -6.0 ]
BS-EN-60898 & BS-EN-61009-1 .
[ Icn ] - is themaximum-fault-current . the device can interrupt safely . …….. [ Icn ] value is normally marked on the device [ 6000 ]
[ Ics ] - is the maximum-fault-current . the device caninterrupt safely without loss of . performance .

6). Breaking-capacity - enter the . protective-device-breaking-capacity . often “printed on the circuit-breakers “ e.g. 6.
For- domestic-installations . the ( PFC ) is unlikely to exceed 6kA . up to which value . [ Icn] will equal [ Ics ]

411.4.7.: where a circuit-breaker . Table- 41.3. for the types & ratings . ofovercurrent-devices . listed may be used . instead of calculation .
wherea circuit-breaker - BS-EN-60898 & BS-EN-61009-1 .
2394: our circuits . are . 411.3.2.2. Maximum-disconnection-times . Final-circuits . Notexceeding 32A . [ 0.4s ]

 

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2394: Am making a Point to Note . can’tstress the importance of GN-3 . with Testing& Inspection . “ simplicity at isbest “

GN-3: Ambient-temperature 10°C . 20°C . ( 2394: regulations - 30°C . 70°C )

GN-3: Table - A4 .
Circuit-breakers. Maximum-measured-earth-fault-loop-impedance ( in Ohms ) at ambient-temperature 10°C . where the overcurrent-device is a circuit-breaker .BS-EN-60898 or RCBO to BE-EN-61009-1 .

Ambient-temperature 10°C
GN-3: in comparison .( C ) 6A - 3.09 . 10A - 1.85 .

(B ) 32A - 1.16 ←
Table- A6 : ambient-temperature - correction-factors . 25°C - 1.06 . Cf .
Note. from - 10°C . 0°C . 5°C . 10°C . 20°C . 25°C . 30°C .
Theambient-correction-factor . of Table - A6 is applied to the .earth-fault-loop-impedances . of tables . A1 / A4 if the ambient-temperature is other than . 10°C

GN-3tells us how to do the Calculations .
Ambient-temperature is 25°C . themeasured-earth-fault-loop-impedance . of a circuit-protected by a . 32A type B- circuit-breaker to BS-EN-60898 . should not exceed . 1.16 x 1.06 = 1.23Ω.

GN-3. Do Not Mix up the .ambient-temperature Table . B.2 - 10°C p.121 . Table . B1 - 20°C . p.120
Regulations- 41.3. : ( C ) 6A - 3.83Ω . 10A- 2.30Ω . as you can see . there’s a difference . Yeah

 

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TT-Installations . “ Protective-devices “

Disconnection-timeof ( 0.2s ) for TT- installation hasbeen introduced in the . 17[SUP]th[/SUP] Edition . This makes the use of an . RCD orCircuit-breaker with a . residual-element . virtually-essential .

 

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UsefulJunk . 2394 :

2008:2011:

Asbefore all Appendices are “ Informative “ other than Appendix 1 . which is “ Normative “ .
Appendix1 is requirement & all others are provided for guidance .

 

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2394: Reminder .

By Definition . p.31 . “ Minor-works “
Additions & Alterations to an . installation that do not extendto the . provision of a new-circuit .

 

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2394: Reminder . “ Minor-works “
p.31: - Examples . include the . Addition of socket-outlet : or Lighting-pointsto an ( Existing-circuit ) therelocation of a . light-switch . etc .

 

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2394: - 559.6.1.9.

Part- 5 : p.178 . A Lighting-installation . shall be appropriate-controlled .
Note : See table - 53.4. p.149 .
Forguidance on the selection of (Suitable-protective . Isolation & Switching-devices)

2394: Can we use . Circuit-breaker - BS-EN-60898 .for Isolation . Functional-switching . Emergency--switching .
BS-EN-60898- Yes . (3) Device is suitable for .on-load-isolation . i.e. disconnectionwhilst carrying . Load-current .

 

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UsefulJunk : 41.3.

Maximum( Zs ) for . Circuit-breakers to . BS-EN-60898 - Overcurrent-characteristicsof . RCBO - BS-EN-61009-1 . for. ( Instantaneous-operating ) givencompliance with the . 0.4s & 5s . disconnection-times at . nominal-voltage . (Uo of 230V )

Characteristics- type - B . ( Zs- Ω ) for device of . rated-current . (In ) 46 / In .
Characteristics- type - C . ( Zs- Ω ) for device of . rated-current . (In ) 23 / In .
Characteristics- type - D . ( Zs- Ω ) for device of . rated-current . (In ) 11.5 / In .

 

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Circuit-breaker- BS-3871 . Still in Use. Obsolete to BS-7671:2011: standards

Whatis the . Maximum-value of ( Zs ) at anominal-voltage . Uo - 230V .
Type- 2 . circuit-breaker . BS-3871 . with a rated-current ( In -30A ) Maximum-value of ( Zs -230V ) is [ 32.8 / In = 32.86 / 30 = 1.1Ω ]

41.3: - 3A . 6A . 10 .
[ Type - B - right hand side of table - 41.3 ] making me . 46/ In

Your Example to work to . Scenario !!. Type - B. circuit-breaker . rated-current ( In ) of 8A .
Overcurrent- characteristic of . RCBO . Maximum-value of ( Zs ) - 230V is 46 / In = 46 / 8 = 5.75Ω . [ 46 ÷ 8 = 5.75Ω ]

 

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Maximum( Zs ) circuit-breakers - BS-3871 . Obsolete to BS-7671:2011: standards
for.( Instantaneous-operating ) givencompliance with the . 0.4s & 5s . disconnection-times at . nominal-voltage . (Uo of 230V )

Type- ( Zs - Ω ) for device of rated-current - ( In )
Type- 1 . 57.5 / In .
Type- 2 . 32.86 / In .
Type- 3 . 23 / In .
Type- 4 . 4.6 / In .

Type- B . 46/ In .
Type- C . 23/ In .
Type- D . 11.5/ In .

 

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Example: Basics .

Maximum-Earth-fault-loop-impedance. Overcurrent-protective-device .

(Zs ) can be found using the formula given . in Appendix - 3 - BS-7671: p.295 .Where :- [ Zs = Uo / Ia ]

Uo ) . is the nominal . a.c. - rms .Line-voltage to earth .
Ia) . is the current-causing-operation . of the protective-device within the specified-time. [ 0.4s or 5s ] obtained from the .manufactures-time / current-characteristics. for this particular-device-type & rating .

Example. manufactures-time / current-characteristics . for a 400A - fuse. to BS-88-2 . gives a value of . ( Ia - 2840A ) for a disconnection-time of 5s .
Usingthe above-formula . the maximum-value of ( Zs ) for a disconnection-time - 5s . & a nominal-voltage ( Uo - 230V ) Now - 230V ÷ 2840A = 0.08Ωs .

 

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Fig- 3A1 . p.296 . …. it is worth keeping the BS-7671:2008:

Fuses: 2008 : complying with these - withdrawn-standswill be found in . existing installations . for years to come .

BS-1361 is → BS-88-3 : fuse-system C .

Table- 41.2. - ( 0.4s ) BS-88-3 :
Table- 41.4. - ( 5s ) BS-88-3 :

Question. Maximum ( Zs ) value for . BS-88-3 . in 41.4 - (b) How these . maximum ( Zs ) values are obtained.
411.4.5.- Formula - ( Zs x Ia ≤ Uo )

Where:
Zs) . Earth-fault-loop-impedance in Ωs
Ia) . Current in amps . which causes the protective-device to operate . withinthe time-specified in table - 41.1. or
Ifappropriate . within the . 5s . disconnection-time-specified in . regulation -411.3.2.3. for TN-system(s)
Wherean RCD . is used . the current ( Ia ) isthe rated-residual-operating-current . which provides disconnection . within thetime specified in . table - 41.1. . or
Ifappropriate . within the . 5s . disconnection-time-specified in . regulation -411.3.2.3. for TN- system(s)

Uo) . Nominal-voltage to Earth . in Volts- 230V for standard . a.c. Single-phase & Three-phase-circuit(s)
Uo- 2011 ) Nominal . a.c. rms or d.c.line-voltage to Earth in volts - ( V )

Appendix- 3 :
Thevalue of ( Ia ) can be obtained by reference to the appropriate . time /current-characteristic of theprotective-devices & RCDs inAppendix - of BS-7671:2011:

20A- BS-88-3 fuses .
Assumewe have a . 230V - TN - a.c. system with. overcurrent-protection . provided by 20A - BS-88-3 . for a final-circuit - not exceeding 32A .
41.1.- requires that disconnection of the circuit . takes place within a .maximum-time of ( 0.4s )

Youron Calculations .
Maximum-earth-fault-loop-impedance - ( Zs ) which will ensure that . 20A - BS-33 fuses will . disconnect the circuit. within - 0.4s
411.4.5. shown above . but transpose . it to make . ( Uo the subject . this gives ) Uo . Zs ≤ Ia . Uo = 230V .

Toobtain ( Ia ) Fig - 3A1 . Appendix - 3 . time/ current-characteristic . for BS-88-3 . fuses .

Fig- 3A1 . I can’t draw a line .
3A1. representing the . 20A - fuse givesus the value of current . ( 113A ) mucheasier to use the table at the .top-right of the page . fromthis table we can see . that the value of current which causes . 20A - BS-88-3 . fuse to operate within. 0.4s is ( 113A ) back to your formula . ( Uo. Zs ≤ Ia 230V ) Zs ≤ 113 . Zs ≤ 2.04Ω .

Table- 41.2. (b) Maximum - Zs . 20A - BS-88-3. fuse is 2.04Ω

Maximum- ( Zs ) Table(s) & Appendix - 3 . relationship between . the current required to. operate the protective-device . & the earth-loop-impedance-values .