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1BS7671 2008 Outcomes AppendicesUse of appendices
8.1 Apply relevant information/data within Appendices A: British
Standards to which reference is made in the Regulations B:
Statutory regulations and associated Memoranda C: Time/Current
characteristics of overcurrent protective devices D:
Current-carrying capacity and voltage drop for cables and flexible
cords E: Classification of external influences F: Electrical
Installation Certificate, Minor Works Certificate and Periodic
Inspection Report G: Harmonized cable core colours H:
Current-carrying capacity and voltage drop for busbar trucking
and
powertrack systems i: Definitions other systems J: Protection of
conductors in parallel against overcurrent K: Effect of harmonic
currents on balanced three-phase systems L: Voltage drop in
consumers installations M: Methods for measuring the insulation
resistance/impedance of floors and
walls to earth or to the protective conductor N: Measurement of
fault loop impedance: consideration of the increase of the
resistance of the conductor with the increase of temperature O:
Ring and Radial final circuit arrangements
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2BS7671 2008:AppendicesAppendix 1 has new and adapted BS EN
numbers and associated
harmonized documentation
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BS7671 2008 appendix 1
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Appendix 2Relationship between statutory bodies
Distributors systems ESQC Regs. 2002
Buildings The building regs. 2000
Non domestic places of work activity EAWR 1989
Cinemas Cinematography regs 1955
Machinery Supply of machinery 1992
Entertainment and theatres Conditions of licence miscellaneous
1982
HV lighting As above
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5Appendix 3Appendix 3 differs in that:16th ed :
17th ed :
The Nominal Open Circuit Voltage is now 230V
BS3871 Type 2 MCBs are no longer included
Maximum Zs Tables in Part 4 have been adjusted to take into
account 240 -> 230V
IaUZ OS
IaUZ OCS
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Appendix 3New table, 3A, Time/current characteristics for BS
EN
61008/9RCD Type
INmA mA
Trip time ms mA
Trip time ms mA
Trip time ms
General Non-delay
G type
10 10 300 max
20 150 max
50 40 max
30 30 60 150
100 100 200 500
300 300 600 1500
500 500 1000 2500
DelayS type
Selective
100 100 130 min500 max
200 60 min200 max
500 40 min150 max300 300 600 1500
500 500 1000 2500
NI1 NI2 NI5
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Instantaneous tripping assume the fastest time, 0.1sec is given
here, see manufacturers data sheets for faster and more accurate
times
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8BS7671 2008:Appendices
Appendix 4 : A new contents page with additional tables (4A3)
Methods of installation of cables have changed from
numbers to lettersExamples: 1. M4 -> A, 2. M3 -> B, 3. M1
and M11 -> C Specific methods for Domestic installations (100,
101,
102: applicable to table 4D5)New formula to assess grouping
factor in enclosures
Where F is the de-rating factor; n is the number of grouped
cables
n1F
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9BS7671 2008: Appendix 4
Simple chart outlining installation methods
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BS7671 2008: Appendix 4Example of install methods for twin and
earth
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11
BS7671 2008: Appendix 4New tables for grouping and ambient
temperature,
buried in the ground
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Appendix 4
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Appendix 4
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Appendix 4
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15
BS7671 2008: Appendix 5Appendix 5 has the same structure and
content as the 16th editionDifferences are:IP ratings
(characteristics of installation) are now includedBS EN cross
referencing is now included
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Appendix 6
ADS
Appendix 6 Model forms of certificationNo changes here except
definitions within the Schedule of inspections
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Appendix 7Appendix 7 : Harmonized colour coding of
conductors
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18
BS7671 2008: Appendix 8
Powertrack and busbar systemsA preassembled trunking with
ridged
copper bars on fixed supports allowing connection to be made at
predetermined intervals via a fused plug socket arrangement.
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Appendix 8Calculations for effective current carrying capacity
follow the
general requirements for :
1. Protection against shock (41)2. Thermal Effects (42)3.
Overcurrent and overload protection (43)4. Volt drop (525), app 12,
para 5 app 8
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20
BS7671 2008: Appendix 8
Current carrying capacity = In (?)Ambient temp = 35CCorrection
factor for ambient temp. > 35C = KCorrection factor for angle of
mounting = KEffective current carrying capacity under new
mounting
conditions and higher than ambient temp. = IzTherefore Iz =>
In x K x KIz => Ib where Ib = design currentIa In where In in
this case is the rating of the OPDVd = (mV/A/m x L x Ib) / 1000
V
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21
BS7671 2008: Appendix 9
Multiple supplies DefinitionsOutlining methods of earthing with
or without NeutralsExample: An AC TN-C-S system
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Appendix 9TN-C-S DC system, earthed midpoint conductor M and
protective conductor is combined in one single conductor as part of
the installation
Reg 8(4) of the Electricity, Safety, Quality and continuity regs
2002 states that a consumer shall not combine the neutral and
protective functions I a single conductor in the consumers
installation
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23
BS7671 2008: Appendix 10
Conductors in Parallel protection against overcurrentUsed to
supply greater currents than the max current
capacity of a single conductordomesticObvious example might be a
ring final circuitIndustrialFeeders where multiple singles are used
or trefoil 3 phase conductors are laid in parallel
(reduces the effects of reactance)
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BS7671 2008: Appendix 10Overload protection
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Appendix 10Overload protection
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BS7671 2008 UpdateShort Circuit Protection
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Appendix 10Short Circuit Protection recommended methodIf one
conductor is damaged then all three are disconnected
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Appendix 11 - Harmonics in 3-phase systems
Harmonic distortion is the change of the supply voltage from the
ideal sinusoidal waveform
Caused by:Interaction of distorting customer loads with the
change in supply
network impedancePrimary effects are:1. Overheating of induction
motors, 2. Overheating of transformers, 3. Damage to PF
capacitors4. Overloading of neutrals5. Interaction of harmonic
currents with power factor
correction capacitors causing gross amplification through
resonance and serious damage to system components
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BS7671 2008: Appendix 11Harmonics on Balanced three phase
systemsFor higher frequency harmonics with conductors < 50mm2
use the
formula:
Use table 11 for 3rd harmonic as shown in examples
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Appendix 11Application of rating factors for triple harmonic
currents
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Appendix 11
Application of rating factors for higher frequency harmonic
currents
Apply formula to following example
A 3 phase 30kW 0.85 pf VSD machine contains within its line
currents 45% 3rd harmonic, 30% 5th harmonic, 20% 9th harmonic and
15% 12th harmonic currents calculate the correction factor/s to be
applied to the conductors
2
LLL
80Harmonicsth12,th9,th5
Harmonicth12Harmonicth9Harmonicth5
A8086.0
345.051Harmonicrd3
A5185.0400732.1
000,30Ipf.I.V.3P
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32
BS7671 2008: Appendix 12
Volt Drop in consumers Installations
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BS7671 2008: Appendix 13
Insulation of floors and walls (from GN3)Taken from GN3
Inspection and Testing
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BS7671 2008: Appendix 14
Temperature effects on the Earth Loop Impedance (GN3)
)3.412.41tablemax.Zs(IU8.0mZ
A
OS
0.8 adjusts for actual operating conditions such as ambient
temperature at the time of fault and the operating temperature of
the cable while the fault is in progress.
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35
Annex to Appendix 14
Calculating Earth Fault Impedances
From OSG table 9A, 9B, 9C = The external impedance found by
enquiry not
recommended or by measurement By enquiry TNS = 0.8, TN-C-S =
0.35, TT = 21 By Measurement: TNS < 0.8, TN-C-S < 0.35, TT
1667
- 200 max BS7671 100 NICEIC All installations RCD protected!
By calculation: As for final circuit calculations plus
manufacturers data plus GN6 protection from overcurrent
Total earth-fault loop impedance:
MLmmRR /)21(
MLRRZeZs )
100021(
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January 08 Legh Richardson 36
Annex to Appendix 14 Calculating Prospective Earth Fault
Currents
Appendix 3, Section 411, 434 For the protective device to
operate correctly the
open circuit voltage at the source of supply must be taken
From Appendix 3 time current characteristics for standard
protective devices show the minimum fault current needed to operate
the protective device and disconnect the circuit within the time to
comply with BS7671
ZsUoIa
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Appendix 15
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BS7671 2008 Appendix 15
Standard Circuit Arrangements for Ring final and Radial
circuits
Standard ring final circuit = 2.5mm2 per legStandard Circuit
Arrangements for rings and radialsRing final circuit designed for
2.5mm2 live conductors and 1.5mm2
for CPC 433.1.5Starts and finishes at the Dist Board1.5mm2 can
be used only if connected on the load side of a SFCU as
a spurSockets must share the loading equally spaced around the
ringNo Space heaters and/or Immersion heatersCookers and other
appliances (?) > 2kW prohibited2.5mm2 conductors for non-fused
spursFloor area < 100m2
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Appendix 15
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BS7671 2008 Appendix 15
Standard Circuit Arrangements for Radial Circuits Applies to
Twin and Earth BS6004 2.5mm2 = 20A OPD, serves an area of 50m2
4.0mm2 = 32mm2 OPD, serves an area of 75m2 4.0mm2 can have 2.5mm2
non fused spurs serving one DSSO 4.0mm2 can have 1.5mm2 fused spurs
serving one DSSO