LOW VOLTAGE EARTHING POLICY AND EART-01-002 APPLICATION .
LOW VOLTAGE EARTHING POLICY ANDAPPLICATION GUIDE1.EART-01-002Issue No. 5SCOPEThis document provides guidance on the approach to be adopted when planning, designing anddelivering all LV network solutions including new networks, fault repairs, modernisation, reinforcementand mixed earthing arrangements.2.ISSUE RECORDThis is a Controlled document. The current version is held on the EN Document Library.It is your responsibility to ensure you work to the current version.Issue DateMarch 2009Issue No.3AuthorColin BrownSeptember 20154Gordon MacKenzieSeptember 20185Gordon MacKenzie3.Amendment DetailsIssue 2 updated with commentsfrom Legal section & generalcommentsIssue 3 general revision. Documentrestructured to support policyapplication.General review of Issue 4 pendingcompletion of Neutral Current Diversionproject in association with PNDC.Updated text for temporary RCDposition section 12.4.Updated reference BS 7671.Updated PME value section 12.4Guidance removed from section 10.4combined HV / LV Earthing.ISSUE AUTHORITYAuthorName: Gordon MacKenzieTitle: Senior Engineer,Engineering Design andStandardsOwnerName: David NeilsonTitle: Network ManagerIssue AuthorityName: Jim McOmishTitle: Head of DistributionNetworksDate: 2/10/184.REVIEWThis is a Controlled document and shall be reviewed as dictated by business or legislative change butat a period of no greater than 3 years from the last issue date.SPEN working in partnership with Strathclyde University and PNDC Network Operators to review theimpact of Neutral Current Diversion on existing Networks constructed in compliance with industryguidance ENA ER G12/4. This document shall be subject to further review on completion of thePNDC project works, which will also include a review of LV Foundation Earthing in association withIET.DISTRIBUTIONThis document is part of the Construction Virtual, SPD and SPM System Design Manuals maintainedby Document Control but does not have a maintained distribution list. It is also published on the SPEnergy Networks website. SP Power Systems LimitedPage 1 of 36
LOW VOLTAGE EARTHING POLICY ANDAPPLICATION GUIDE5.EART-01-002Issue No. 5CONTENTS1. SCOPE . 12. ISSUE RECORD . 13. ISSUE AUTHORITY . 14. REVIEW . 1DISTRIBUTION . 15. CONTENTS . 26. REFERENCE AND RELATED DOCUMENTS . 47. INTRODUCTION. 48. REGULATIONS AND GUIDANCE DOCUMENTS . 58.1ESQCR . 58.2Engineering Recommendation G12/4 . 58.3BS7671 – Requirements for Electrical Installations . 68.4Types of Network and Service Connection . 69. NEUTRAL AND EARTH CONNECTIONS . 1210. EARTHING FOR NEW LV NETWORKS. 1310.1 Underground Mains Distribution . 1510.2 Overhead Mains Distribution . 1510.3 Services . 1610.4 Combination or Segregation of HV & LV Earth Electrodes . 1611. EARTHING FOR EXISTING/MODIFIED LV NETWORKS . 1611.1 Refurbishment/Modernisation . 1611.2 Network Alterations . 1711.3 Repair . 1811.4 Use of Water pipes as an Earth Terminal . 1812. EARTH LOOP IMPEDANCE . 1912.1 Measurement . 1912.2 Recording . 1912.3 Typical Maximum Values . 1912.4 High Earth Loop Impedance Resolution . 1913. LOAD BALANCE . 2114. MULTI-OCCUPANCY BUILDINGS . 2114.1 Domestic . 2114.2 Commercial/Industrial . 2515. PROVISION OF CUSTOMER EARTH TERMINAL . 2515.1 New Connections . 2515.2 Cut-out replacement . 2615.3 Customer Request . 26 SP Power Systems LimitedPage 2 of 36
LOW VOLTAGE EARTHING POLICY ANDAPPLICATION GUIDEEART-01-002Issue No. 515.4 Repair/Refurbishment . 2616. SPECIAL SITUATIONS . 2716.1 LV Supplies associated with Tramways and Railways . 2716.2 Construction Sites . 2716.3 Temporary Supplies (not associated with construction sites) . 2816.4 Agricultural & Horticultural Premises . 2916.5 Swimming Pools, . 2916.6 Caravans Boats & Marinas . 3016.7 Mobile Homes . 3016.8 Mines & Quarries. 3016.9 Petrol Filling Stations . 3016.10 Street Lighting and road signs with electrical load of 500W or less . 3016.11 Street Electrical fixtures not covered by section 16.10 . 3216.12 Substation Auxiliary Supplies . 33 SP Power Systems LimitedPage 3 of 36
LOW VOLTAGE EARTHING POLICY ANDAPPLICATION GUIDE6.EART-01-002Issue No. 5REFERENCE AND RELATED DOCUMENTSElectricity Safety Quality & Continuity Regulations 2002 (as amended)Electricity Supply Regulations 1988Energy Networks Association Engineering Recommendation G12/4Energy Networks Association Engineering Recommendation G87Energy Networks Association Engineering Recommendation P23Energy Networks Association Engineering Recommendation G39BS 7909 Code of Practice for: Design and installation of temporary distribution systems delivering acelectrical supplies for lighting, technical services and other entertainment related purposesBS 7430 2011 Code of Practice for Protective Earthing of Electrical InstallationsBS 7671 2018 Requirements for Electrical Installations IET Wiring Regulations Eighteenth EditionRegulations for the Electrical Equipment of Buildings Fourteenth Edition (incorporating amendments1970 and 1974)HSE Guidance Mines & QuarriesHSE Guidance Petrol StationsSecondary Substations Earthing Design & Construction Policy (Document not available at time of publishing)ESDD-01-006 Standard Low Voltage Connection ArrangementsESDD-02-003 Low Voltage Connection Arrangements in Residential DevelopmentsESDD-02-012 Framework for Design & Planning of LV Housing Developments, including U/GNetworks and Associated HV/LV S/SESDD-04-003 Service Design for the Connection of Commercial, Industrial and ResidentialPropertiesOPSAF-12-061 Low Voltage Mains / Service Continuity and Polarity Testing7.INTRODUCTIONThis policy describes the requirements for the earthing of Low Voltage Distribution Networks in the SPEnergy Networks Licence areas.The earthing arrangements on LV networks should be checked to see whether it is to the standarddescribed in this document whenever any of the following situations occur when:i)ii)iii)iv)v)Connecting a new substation or recovering an existing substation.Changing a transformer in an existing substation.Reinforcing or extending the network.Repairing the network.Customers' earthing facilities which are provided via metallic water pipes are about to berendered ineffective by the insertion of non-metallic pipes in distributors or service pipesby the Water Company or plumbing contractors.vi) The theft of earth-wires or conductors has rendered earthing ineffective.Non-standard or incorrect legacy earthing application should be rectified as per the requirements ofthis document. SP Power Systems LimitedPage 4 of 36
LOW VOLTAGE EARTHING POLICY ANDAPPLICATION GUIDE8.EART-01-002Issue No. 5REGULATIONS AND GUIDANCE DOCUMENTSThe configuration and design of LV networks has changed over the years as have the requirementsfor the earthing on the network and in customers’ installations. New LV networks shall be designedusing Protective Multiple Earthing (PME), whereas extensions and additions to existing LV networksmust take account of the existing network conditions and the customer connections. The overridingconsideration when planning or carrying out alterations must be the safety of customers andcompliance with the requirements of the Electricity Safety Quality and Continuity Regulations(ESQCR). Replacement of service connections on a ‘like for like’ basis without achieving compliancewith the requirements of the ESQCR is not acceptable. The key aspects of the ESQCR relating to LVearthing are described below.8.1ESQCRRegulation 8(3) (b) and (c) require that: Every supply neutral conductor is connected with earth at, or as near as is reasonablypracticable to, the source of voltage except that where there is only one point in a network atwhich consumer’s installations are connected to a single source of voltage, that connectionmay be made at that point, or at another point nearer to the source of voltage; and No impedance is inserted in any connection with earth of a low voltage network other thanthat required for the operation of switching devices or of instruments or equipment for control,telemetry or metering.The application of Protective Multiple Earthing is governed by Regulation 9 which identifies therequirements in regulation 9(2)(a) and (b) which require that: ‘In addition to the neutral with earthconnection required under Regulation 8(3)(b) a distributor shall ensure that the supply neutralconductor is connected with earth at: a point no closer to the distributor’s source of voltage (as measured along the distributingmain) than the junction between the distributing main and the service line which is mostremote from the source: and such other points as may be necessary to prevent, so far as is reasonably practicable, the riskof danger arising from the supply neutral conductor becoming open circuit.’In addition Regulation 9(4) requires: The distributor shall not connect his combined neutral andprotective conductor to any metalwork in a caravan or boat.It is a requirement of the Electricity Safety Quality and Continuity Regulations, regulation 24 (4) & (5)that: Unless he can reasonably conclude that it is inappropriate for reasons of safety a distributorshall, when providing a new connection at low voltage, make available his supply neutralconductor or, if appropriate, the protective conductor of his network for connection to theprotective conductor of the consumer’s installation. In this regulation the expression ‘new connection’ means the first electric line, or thereplacement of an existing electric line, to one or more consumer’s installations.In terms of the Electricity Safety Quality & Continuity Regulations an ‘electric line’ is defined as, any line which is used or intended to be used for carrying electricity for any purpose andincludes, unless the context otherwise requires:o any equipment connected to any such line for the purpose of carrying electricity; ando any wire, cable, tube, pipe, insulator or other similar thing (including its casing orcoating) which supports, or is associated with any such line.8.2Engineering Recommendation G12/4The guidance notes issued at the time the ESQCR came into force state that compliance with therequirements of Regulation 9, covering the application of PME to LV networks where the neutral andprotective functions are combined, can be demonstrated by adopting the requirements of EngineeringRecommendation G12/3 subsequently amended to G12/4. This Engineering Recommendation SP Power Systems LimitedPage 5 of 36
LOW VOLTAGE EARTHING POLICY ANDAPPLICATION GUIDEEART-01-002Issue No. 5provides guidance on the application of Protective Multiple Earthing to an LV network and as such willbe referenced extensively within this policy document.8.3BS7671 – Requirements for Electrical InstallationsBS 7671 Requirements for Electrical Installations otherwise known as the Wiring Regulations sets outthe requirements which should be met by a customer’s LV electrical installation in order to ensuresafety. Within these requirements are those for the equipotential bonding required between theinstallation’s earthing conductor and extraneous conductive parts within a customer’s premises.The use of a new earth terminal by any customer connected to the SPEN LV distribution network iscontingent upon their compliance with the equipotential bonding requirements of the wiringregulations at the time their installation is connected to the terminal.Table 1 – Requirements for equipotential bonding conductors in customer installations(table 54.8 BS 7671 2018)Copper Equivalent cross-sectional area of theMinimum copper equivalent cross-sectionalsupply neutral conductorarea of the main protective bondingconductor2235mm or less10mm222Over 35mm up to 50mm16mm222Over 50mm up to 95mm25mm222Over 95mm up to 150mm35mm2Over 150mm50mmEquipotential bonding is required between the earth conductor and the following extraneousconductive parts: Water installation pipes Gas installation pipes Other installations pipework and ducting Central heating and air condition systems Exposed metallic structural parts of the building8.4Types of Network and Service ConnectionThere are typically four basic kinds of LV service connection which can be found on the SPEN LVnetworks.8.4.1TN-C-STN-C-S connections are associated with networks comprising combined neutral earth cables wherethe neutral and earth functions are combined in a single conductor. This type of cable is used in theconstruction of all new Protective Multiple Earthing (PME) networks and such a supply is oftenreferred to as a PME supply.PME is not necessarily defined by the type of cable used or limited to a specific type of cable ratherby the fact that the neutral conductor, which may or may not also be the only earth conductor in thecable, is connected to earth at multiple points within the network. A feeder constructed using aCombined Neutral Earth cable must comply with the requirements of PME regulations in the ESQCRas described above, whereas a feeder comprising separate neutral and earth conductors need notcomply with the requirements to earth the neutral at more than one location beyond the voltagesource.Figure 1 (reproduced with permission from ENA Engineering Recommendation G12/4) illustrateswhere PME facilities may be provided in the case of hybrid networks where a mixture of SNE andCNE cables have been installed over time. SP Power Systems LimitedPage 6 of 36
LOW VOLTAGE EARTHING POLICY ANDAPPLICATION GUIDEEART-01-002Issue No. 5TERMINOLOGY:S/S SubstationL/B Link disconnecting Box (phase normally open, neutral solid)CNE Combined Neutral Earth cableSNE Separate Neutral Earth cable PME neutral earth electrode Bond between sheath of SNE cable and Neutral of CNE cablePME facilitiesavailableExamplesS/S1SNEEarth electrodewhere necessaryS/SS/SCNE3S/S4S/S5On CNE sectiononlySNECNE2Along whole lengthof distributorCNEL/BSNESNESNECNESNESNES/SAlong whole lengthof distributors fromboth substationsAlong whole route ofmain distributor butnot branchOn CNE branch &main distributorbetween S/S andCNE/SNE jointCNES/S6SNECNESNEEarth electrodewhere necessaryS/S7Between S/S andneutral sheath bondmost remote fromS/SBetween S/S andservice joint positionSNEEarth electrodewhere necessaryFigure 1 Locations where PME facilities may be made available(ENA ER G12/4 Figure 4.5) SP Power Systems LimitedPage 7 of 36
LOW VOLTAGE EARTHING POLICY ANDAPPLICATION GUIDEEART-01-002Issue No. 5Figure 2 TN-C-S supply arrangements.8.4.2TNSA TNS supply has a separate neutral and earth conductors between the service point and the neutralearth connection at the source of the main distributor cable. SP Power Systems LimitedPage 8 of 36
LOW VOLTAGE EARTHING POLICY ANDAPPLICATION GUIDEFigure 3 TNS Supply Arrangement SP Power Systems LimitedPage 9 of 36EART-01-002Issue No. 5
LOW VOLTAGE EARTHING POLICY ANDAPPLICATION GUIDE8.4.3EART-01-002Issue No. 5TTIn a TT supply the customer’s earth terminal is electrically separate from the SPEN network. In LVnetworks where only the phase and neutral conductor is distributed and the neutral is not multipleearthed it is essential that the customer provide their own earth terminal to which the protectiveconductors of their installation must be connected and that this remains separate from the SPENnetwork.Figure 4 TT Supply arrangements SP Power Systems LimitedPage 10 of 36
LOW VOLTAGE EARTHING POLICY ANDAPPLICATION GUIDE8.4.4EART-01-002Issue No. 5Protective Neutral Bonding (
delivering all LV network solutions including new networks, fault repairs, modernisation, reinforcement and mixed earthing arrangements. 2. ISSUE RECORD This is a Controlled document. The current version is held on the EN Document Library. It is your responsibility to ensure you work to the current version. Issue Date Issue No. Author Amendment Details March 2009 3 Colin Brown Issue 2 updated .
set-ups. One of the key essential requirements for designing an adequate earthing system is to have as low value as possible of resistance to remote earth in order to . include the earthing resistance and the minimum size of the earthing conductor, which can be calculated using various methods as part of the design methodology. Lim, S. C. and .
Guidelines for the design, installation, testing and maintenance of main earthing systems in substations . ENA Technical Specification 41-24 Issue 2 - November 2018 . changes to earthing practice as outlined in Electrical Safety, Quality, and Continuity Regulations (ESQCR), in particular with regard to smaller distribution or secondary .
from electric shock. Bonding and earthing are often confused as the same thing. Sometimes the term Zearth bonding is used and this complicates things further as the earthing and bonding are two separate connections. Bonding is a connection of metallic parts with a Zprotective bonding conductor. Heres an example shown below.
Service support: find your nearest Vacon service center at www.vacon.com 1 1.3 Earthing and earth fault protection The Vacon 100 X AC drive must always be earthed with an earthing conductor connected to the earthing terminal marked with . Since the touch current exceeds 3.
Where applicable (e.g. transformers) earthing tests must be performed at each earthing point, and the test results recorded on DCF 4.1 before energising. The completed earthing test forms must accomp
concerned with earthing practices and design for outdoor 400 kV AC substation for power frequency of 50 Hz [1, 2] 1.1 IMPORTANCE The earthing system in a plant / facility is very important for a few reasons, all of which are related to either
provided for staff working on electrical equipment. Despite an obvious need, earthing is barely covered during engineering degree courses. It is also difficult to obtain up to date, reliable information on the subject. For example, if one consults books on building services or electrical substation design, the chapter on earthing is
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