bs7671 2015 outcomes appendices - legh richardson...

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BS7671 2015 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: harmonic currents moved to appendix 4 • L: Voltage drop moved to appendix 4 • 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 • P: SPD arrangements

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BS7671 2015:AppendicesAppendix 1 has new and adapted BS EN numbers and associated

harmonized documentation

BS7671 2015 appendix 1

Appendix 2Relationship between statutory bodies

As aboveHV lighting

Conditions of licence miscellaneous 1982Entertainment and theatres

Supply of machinery 1992Machinery

Cinematography regs 1955Cinemas

EAWR 1989Non domestic places of work activity

The building regs. 2000Buildings

ESQC Regs. 2002Distributors systems

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Appendix 3Appendix 3 differs in that:16th ed :

17th ed :

•The Nominal Open Circuit Voltage is now 230V * 0.95•BS3871 -> BS EN 60898 and 61009•BS1361 -> BS 88-3

•Maximum Zs Tables in Part 4 have been adjusted to take into account the minimum likely voltage 240 -> 230V -> 218.5V

Iamin.C*UZ O

S

IaUZ OC

S

Appendix 3New table, 3A, Time/current characteristics for BS EN

61008/9

25001000500500

1500600300300

40 min150 max

50060 min200 max

200130 min500 max

100100Delay‘S’ type

Selective

25001000500500

1500600300300

500200100100

150603030

40 max50150 max

20300 max

1010General Non-delay

‘G’ type

Trip time msmA

Trip time msmA

Trip time msmA

IΔNmA

RCD Type

NI1 NI2 NI5

Appendix 3

Instantaneous tripping assume the fastest time, 0.1sec is given here, see manufacturer’s data sheets for faster and more accurate times

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BS7671 2015: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

nCg 1

Appendix 4 - 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

BS7671 2015: Appendix 4Harmonics on Balanced three phase systemsFor higher frequency harmonics with conductors < 50mm2 use the

formula:

Use table 11 for 3rd harmonic as shown in examples

Appendix 4Application of rating factors for triple harmonic currents

Appendix 4

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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BS7671 2015: Appendix 4

Volt Drop in consumers Installations

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Simple chart outlining installation methods

BS7671 2015: Appendix 4Example of install methods for twin and earth

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BS7671 2015: Appendix 4New tables for grouping and ambient temperature,

buried in the ground

Appendix 4

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BS7671 2015: 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

Appendix 6Model forms of certificationChanges in the number of items to be inspected – EIC and EICR

Appendix 6Model forms of certification: Changes to Minor Works Certificate - MWC

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Appendix 7Appendix 7 : Harmonized colour coding of conductors

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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.

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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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 <= 1.45 x IzIz => 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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Multiple supplies – DefinitionsOutlining methods of earthing with or without NeutralsExample: An AC TN-C-S system

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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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)

Appendix 10Overload protection

BS7671 2015 UpdateShort Circuit Protection

Appendix 10Short Circuit Protection – recommended methodIf one conductor is damaged then all three are disconnected

Appendix 13

Insulation of floors and walls (from GN3)Taken from GN3 Inspection and Testing


Temperature effects on the Earth Loop Impedance (GN3)

)..tablemax.Zs(I

min.CU.mZA

OS 34124180

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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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 100Ω NICEIC – All installations RCD protected!

– By calculation: As for final circuit calculations plus manufacturer’s data plus GN6 protection from overcurrent

Total earth-fault loop impedance:

MLmmRR /)21(

MLRRZeZs )

100021(

January 08 Legh Richardson 37

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

Appendix 15

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

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

BS7671 2008 Appendix 16Arrangements for Surge Protective Devices (SPDs)


Arrangements for Surge Protective Devices (SPDs)


Surge Protective Device Classification

Near terminal equipmentTYPE 3SPD tested with a

combination wave

At distribution boardsTYPE 2SPD tested with In

Origin of installationTYPE 1SPD tested with Iimp

SPD InstallationSPD

To BS EN 61643-11SPD

To BS EN 62305


Arrangements for Surge Protective Devices (SPDs)

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