DEHN Surge ProtectionSelection guide to meet the requirements of18th edition BS7671

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Where is Surge Protection Required?

Paragraph 443.4 of the 18th edition states that “Protection against transient overvoltages shall be provided where the consequences caused by overvoltage:-

A) results in serious Injury to, or loss of, human life, or: B) results in interruption of public services and/or damage to cultural heritage, or: C) results in interruption of commercial or industrial activity, or: D) affects a large number of co-located individuals.

For all other cases, a risk assessment according to Regulation 443.5 shall be performed in order to determine if protection against transient overvoltage is required. If the risk assessment is not performed, the electrical installation shall be provided with protection, except for single dwellings where the total value of the installation therein does not justify such protection.”

BS7671 / 18th Edition of the Wiring Regulations

Changes to the requirement for surge protection in sections 443 and 534

When are the changes to BS7671,18th Edition Wiring Regulations coming into effect?

On the 1st July 2018, the UK’s wiring regulations (BS7671) will be amended and the 18th edition released.

The amendments in this edition will have an important impact on electrical installations as among the changes are updates that will now make surge protection devices (SPD’s) a requirement to be installed. Other changes will make additional SPD’s a requirement further downstream and they will also affect what type of SPD’s can be installed as per the Lightning Protection Zones (LPZ) concept. We have set out a basic guide to the amendments below to help raise awareness to these changes.

HES

LPZ 3

LPZ 2

LPZ 2

LPZ 2

LPZ 2

LPZ 0B

LPZ 0B

LPZ 1

LPZ 1

LPZ 1

LPZ 0A

MEB

equipotential bonding

air-termination system

metal supply line

shielding

lightning equipotential bondinglightning current arrester (type 1)

local equipotential bondingsurge arrester (type 2/3)

lightning protection zone

main earthing busbar

low-voltage supply system

information technology system

MEB

What surge protection is required?

If the structure has external lightning protection installed then SPD’s shall be fitted where the cables enter/leave the structure. These SPD’s shall be type 1 - See section 534.4.1.3 In all other cases fit type 2 SPD’s at the origin of the electrical installation or where cables cross zonal interfaces as in section 534.4.1.2.

Then in section 534.4.1.5 further type 2 or Type 3 SPDs shall be located in the fixed electrical installation, for example, in sub distribution boards or close to the equipment to be protected, to ensure the required voltage protection level is maintained throughout the installation.

The changes in section 534.4.5.1 introduces a new term (SPDA) or surge protection device assembly this focuses on the performance of the SPD circuit so that includes the connected OCPD and the cables. The standard emphasizes that high surge impulse current values, for example 12.5kA for type 1 SPD are not being de-rated by undersized OCPD for example a MCB rated at just 6kA. This same section looks at lower voltage protection levels achieved by built in fusing for example see note 2 in section 534.4.4.2 and the DEHN CI SPD range with integrated fuses.

Why is surge protection required?

Surge protection is increasingly important because:

• Technical devices are becoming more and more sensitive – i.e. they are easily damaged in case of surges. For example, LED lights have a lower voltage withstand than the old florescent fittings that they replaced.

• An increasing amount of expensive electronic and Information technology devices are now being used – i.e. device replacement and loss of service is costly.

• Instrument functions are becoming more dependent on online access – i.e. nothing works without a functioning infrastructure. For example, every connected home or smart home is dependent on a working router or modem.

Type 2 SPN SPDDEHNguard TNDG M TN 275Part No. 952 200

Type 2 TPN SPD with integrated fusesDEHNguardDG M TNS CI 275 FMPart No. DSP2PA415CI

DEHN has a range of SPDs installed in IP65 rated enclosures that feature clear lids to show status indication of the device. The DSP range also has the options of SPDs with integrated fusing and so satisfying the requirements of the 18th edition for SPDA or surge protection device assembly.

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Surge protection in BS7671 to the LPZ conceptsection 443.4 overvoltage controlStart position

Protection against transient overvoltage‘s shall be provided where the consequence caused by over voltage:

(a)

(b)

(c)

(d)

results in serious injury to, or loss of, human life, or

results in interuption of public services and/or damage to cultural heritage, or

results in interuption of commercial or industrial activity, or

affects a large number of colocated individuals.

If the above consequences are met Is there a Lightning Protection System to BSEN 62305?

Yes

Then determine level of protectionFollow LPZ concept in section 534 For LPL 1 to 4 For LPL 3 and 4 only

No

Fit type 1/2 SPD from LPZ 0 to 1SPD is surge protective deviceSPDA is a SPD with built in OCPD/ fusessection 534.4.4.2 refers

Part numbers shown without / with remote contacts

Then fit type 2 SPD at LPZ 1-2At further DBsSPDA is a SPD with built in OCPD/ fusessection 534.4.4.2 refers

TPN TN fit type 1/ 2951 400/405 SPDor 961 200/205 SPDASPN TN type 1 /2Contact DEHN

TPN TN type 1/ 2941 400/405or 961 200/205 SPDASPN TN type 1/ 2941 200/205

Fit Type 2 SPD at all further zonal interfacessee section 534.4.1.1 to 534.4.1.5

Then fit type 2 or type 3 SPD at LPZ 2-3Closer to the sensitive equipment

Fit Type 2 and/ or 3 SPD at further zonal interfacessee section 534.4.1.1 to 534.4.1.5

Type 2TPN fit 952 400/405SPN fit 952 200/205

Type 3TPN fit 953 400/405SPN fit 953 200/205

SPDTPN fit 952 400/405SPN fit 952 200/205

SPDATPN fit 952 401/406SPN fit 952 173/178

Yellowline SPDs for communication and datalines

922 400 for single linetelephone applications

907 400 for multipletelephone lines (LSA Strip)

929 121 for Ethernet,CAT5, CAT6 and PoE.

For applications not covered by those listed consequences use, risk assessment in 443.5to determine CRL and then start flow chart from same position. SPDs required if CRL<1000.

SPDs also required if the CRL is not calculated

Fit Type 2 SPD at all cables entering buildingsee section 534.4.1.1 to 534.4.1.5

address data cables /comms entering buildingYes No

Fit Type 2 SPD at all further DBsif last SPD is greater than 10m away

Type 2 SPDTPN fit 952 400/405SPN fit 952 200/205

Type 3 SPDTPN fit 953 400/405SPN fit 953 200/205

address data cables / comms entering building

SPDTPN fit 952 400/405SPN fit 952 200/205

SPDATPN fit 952 401/406SPN fit 952 173/178

Any further DBs?

Yellowline SPDs for TV and CCTV applications

909 706 five channel SPDfor satellite installations

909 711 for BNC video camerasand recording equipment

Fit Type 2 and/or 3 SPDif sensitive end load greater than 10m awaysee section 534.4.4.2

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TYPE 1/2 combined Lightning and Surge arresters

DEHNventil® M TN 255 (951 200/205*)Modular combined lightning current and surge arrester for single-phase TN systems

DEHNventil® M TN 255 FM (951 400/405*)Modular combined lightning current and surge arrester for three-phase systems

* available with volt free contacts for remote monitoring

DEHNshield® DSH TN 255 (941 200/205*)Application-optimised and prewired combined lightning current and surge arrester for single-phase TN systems.

DEHNshield® DSH TNS 255 (941 400/405*)Application-optimised and prewired combined lightning current and surge arrester for TN-S systems.

* available with volt free contacts for remote monitoring

DEHNvenCI 1 255 (961 200)Type 1 combined arrester with integrated backup fuse

DEHNvenCI 1 255 FM (961 205)With remote signalling contact for control device (floating changeover contact)

DEHNvenCI (SPDA) Surge Protection Device Assembly

TYPE 2 Surge protection devices

DEHNguard® M TN 255 (952 200)Modular surge arrester for single-phase 230 V TN systems

DEHNguard® M TN 255 FM (952 205)With remote signalling contact for control device (floating changeover contact)

DEHNguard® M TNS 255 (952 400)Modular surge arrester for three-phase systems

DEHNguard® M TNS 255 FM (952 405)With remote signalling contact for control device (floating changeover contact)

DEHNguardCI (SPDA)

DEHNguard® CI 275 (952 173/178*)Modular surge arrester with integrated fuse for single-phase 230V TN sytems

DEHNguard® CI 275 (952 401/406*)Modular surge arrester with integrated fuse for three-phase sytems

* available with volt free contacts for remote monitoring

Meets requirements of integrated (SPDA) surge protection device assembly. SPDs for TT supplies In all the cases listed within the flowchart and listed above, there is a TT version of the SPD for TT supplies, please call DEHN UK office or refer to the DEHN website. This will ensure compliance to the requirements of the CT2 connection method in regulation 534.4.3.2

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