1、BS 7856:2017Specification for special design and other features of alternating current watthour meters for active energy for use in the UK (Accuracy Classes A and B)BSI Standards PublicationWB11885_BSI_StandardCovs_2013_AW.indd 1 15/05/2013 15:06Publishing and copyright informationThe BSI copyright
2、notice displayed in this document indicates when the document was last issued. The British Standards Institution 2017Published by BSI Standards Limited 2017ISBN 978 0 580 95803 8ICS 17.220.20The following BSI references relate to the work on this document: Committee reference PEL/13 Draft for commen
3、t 16/30348626 DCAmendments/corrigenda issued since publicationDate Text affected BS 7856:2017 BRITISH STANDARD THE BRITISH STANDARDS INSTITUTION 2017 ALL RIGHTS RESERVEDForeword ii1 Scope 12 Normative references 13 Terms and definitions 14 Mechanical features 2Table 1 Dimensions and spacing of fixin
4、g holes and terminals 3Figure 1 Spacing of fixing holes and terminals for single-phase, two-wire meter 45 Electrical features 5Table 2 Standard currents for meters of Class A or Class B 5Figure 2 Diagrams of connections for a single-phase, two-wire, one-rate meter 7Figure 3 Diagrams of connections a
5、nd graphical symbols for a two-element meter used on three-wire systems 8Figure 4 Diagrams of connections and graphical symbols for a two-element meter used on a two-phase, four-wire system 9Figure 5 Diagrams of connections and graphical symbols for a three-element meter used on a three-phase, four-
6、wire system 106 Other features 11Annex A (normative) Test method of a terminals ability to safely clamp standard UK cables 12Figure A.1 Test arrangement for clamping ability of a meter terminal 13Annex B (normative) External rate switching logic for multi-rate meters 14Table B.1 Sequence for multi-r
7、ate registers having two to eight rates 14Annex C (normative) Long-term overcurrent test requirements 15Annex D (normative) Performance criteria for load switches inside meters 16Table D.1 Performance criteria for supply control and load control switches 16Figure D.1 Polyphase meter supply control s
8、witch test timing 17Figure D.2 Contact resistance derived from mV drop measured at meter terminals at Imax18Annex E (normative) Sealing criteria 19Annex F (informative) Operational considerations related to switches inside meters 20Figure F.1 Typical heating in a 100 AImaxmeter when subjected to 1.4
9、5 * Imax21Table F.1 Thermal stresses on a 100 A SCS protected by various OCPD ratings 22Table F.2 Characteristics of OCPDs in common domestic use in the UK 23Figure F.2 Current levels for determining OCPD characteristics 24Bibliography 26Contents PageSummary of pagesThis document comprises a front c
10、over, and inside front cover, pages i to iv, pages 1 to 26, an inside back cover and a back cover.BRITISH STANDARD BS 7856:2017 THE BRITISH STANDARDS INSTITUTION 2017 ALL RIGHTS RESERVED IForewordPublishing informationThis British Standard is published by BSI Standards Limited, under licence from Th
11、e British Standards Institution, and came into effect on 31 July 2017. It was prepared by Technical Committee PEL/13, Electricity meters. A list of organizations represented on this committee can be obtained on request to its secretary.SupersessionThis British Standard supersedes BS 7856:2013, which
12、 is withdrawn.Relationship with other publicationsThe standard specifies several conditions which are more stringent than currently exist within other European metering standards, reflecting the differences in working practices that exist between the United Kingdom and other European Union member st
13、ates. It is, however, important to note that this British Standard is intended to augment the provisions of certain European standards (see Clause 2, “Normative references”) and so, in instances where this document is non-prescriptive, the provisions of these other standards prevail and are therefor
14、e to be taken into account.Information about this documentThis standard has been revised to take account of the introduction of the IEC standard for electricity meter safety (IEC 62052-31) and developments in the UK metering market, principally the roll-out of smart metering to the residential marke
15、t. The decision to further revise the standard came about because of: the incorporation of a supply control switch in every meter, particularly with regard to design considerations related to appropriate utilization categories, switch life (endurance) concerns and the thermal stresses placed upon su
16、ch switches during overcurrent episodes. Furthermore, to give advice relating to supply control switches within polyphase meters in order to avoid issues due to partial switching arising from fault conditions; the inadequacies of some forms of service fusing as a means of providing protection to met
17、ering equipment and the need to align the overload requirements with British national specifications e.g. 1.45 Imax; the need to ensure that the provisions for installation sealing arrangements continue to meet the national specifications within the MOCOPA N1.In addition, legacy sections relating to
18、 meters of older design have been removed. Reference to current transformer operated metering has also been removed as the majority of the standard no longer applies to such metering equipment. However, at the time of writing, consideration is being given to additional work to incorporate current tr
19、ansformer operated metering in an additional standard.The decision has also been taken to convert BS 7856 from a Code of Practice to a Specification as some of the new requirements relating to the national specifications are normative and safety related.Presentational conventionsThe provisions of th
20、is standard are presented in roman (i.e. upright) type. Its requirements are expressed in sentences in which the principal auxiliary verb is “shall”.BS 7856:2017 BRITISH STANDARDII THE BRITISH STANDARDS INSTITUTION 2017 ALL RIGHTS RESERVEDCommentary, explanation and general informative material is p
21、resented in smaller italic type, and does not constitute a normative element.Where words have alternative spellings, the preferred spelling of the Shorter Oxford English Dictionary is used (e.g. “organization” rather than “organisation”).Requirements in this standard are drafted in accordance with R
22、ules for the structure and drafting of UK standards, subclause G.1.1, which states, “Requirements should be expressed using wording such as: When tested as described in Annex A, the product shall .”. This means that only those products that are capable of passing the specified test will be deemed to
23、 conform to this standard.Contractual and legal considerationsThis publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application.Compliance with a British Standard cannot confer immunity from legal obligations.BRITISH STANDARD B
24、S 7856:2017 THE BRITISH STANDARDS INSTITUTION 2017 ALL RIGHTS RESERVED IIITHIS PAGE DELIBERATELY LEFT BLANKBS 7856:2017 BRITISH STANDARD1 ScopeThis British Standard specifies requirements for special design and other features of newly manufactured directly connected alternating current watthour mete
25、rs with ratings up to and including 100 A Imaxfor installation in domestic and small commercial/industrial premises.This standard is principally aimed at the UK market, although it might also be of use to other markets. Within the UK the standard is aimed at manufacturers who intend to design and ma
26、rket meters, meter operators engaged in meter installation activities and those involved in meter procurement, such as energy suppliers and meter asset providers.2 Normative referencesThe following documents are referred to in the text in such a way that some or all of their content constitutes prov
27、isions of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document, including any amendments, applies.Standards publicationsBS 6004:2012, Electric cables PVC insulated and PVC sheathed cables for voltages up to and inc
28、luding 300/500 V, for electric power and lightingBS EN 50470-1:2006, Electricity metering equipment (a.c.) Part 1: General requirements, tests and test conditions Metering equipment (Class indexes A, B and C)BS EN 50470-2:2006, Electricity metering equipment (a.c.) Part 2: Particular requirements El
29、ectromechanical meters for active energy (Class indexes A and B)BS EN 50470-3:2006, Electricity metering equipment (a.c.) Part 3: Particular requirements Static meters for active energy (Class indexes A, B and C)BS EN 60947-1:2007+A2:2014, Low-voltage switchgear and controlgear Part 1: General rules
30、BS EN 62052-11, Electricity metering equipment (AC) General requirements, tests and test conditions Part 11: Metering equipmentBS EN 62052-31:2016, Electricity metering equipment (AC) General requirements, tests and test conditions Part 31: Product safety requirements and testsIEC 60502-1, Power cab
31、les with extruded insulation and their accessories for rated voltages from 1 kV (Um= 1,2 kV) up to 30 kV (Um= 36 kV) Part 1: Cables for rated voltages of 1 kV (Um= 1,2 kV) and 3 kV (Um= 3,6 kV)Other publicationsN1 MOCOPA, Meter Operation Code of Practice Agreement, www.mocopa.org.ukN2 WELMEC, Guide
32、for sealing of Utility meters, WELMEC 11.3 Issue 1 May 20123 Terms and definitionsFor the purposes of this British Standard the terms and definitions given in BS EN 50470 (all parts):2006, BS EN 62052-11, BS EN 62052-31, IEC 60502-1 and the following apply.BRITISH STANDARD BS 7856:2017 THE BRITISH S
33、TANDARDS INSTITUTION 2017 ALL RIGHTS RESERVED 13.1 overcurrent protection device (OCPD)device providing protection against both overload and short-circuit current that is capable of breaking and, for a circuit-breaker, making any overcurrent up to and including the prospective short-circuit current
34、at the point where the device is installedSOURCE: IEC 60364-4-43, 432.14 Mechanical features4.1 For a single-phase, two-wire meter:a) the overall dimensions of the meter and spacing of fixing holes shall be in accordance with the appropriate values given in Table 1; andb) the dimensions and spacing
35、of the current terminals shall be in accordance with the appropriate values given in Table 1 and shown in Figure 1.NOTE Not referred to in Table 1 or Figure 1 but where fitted, auxiliary terminal(s) for single-phase directly connected meters should preferably be provided on the right-hand side of th
36、e terminal block, enabling auxiliary wiring to clear 18 mm to the right of a vertical line which is central to the four main terminals.For polyphase meters, the current terminals of directly connected meters having rated currents up to and including 100 A, shall be in accordance with dimensions K an
37、d L and also conform to P given in Table 1.For any current terminal, into which a correctly prepared cable conforming to BS 6004:2012, 8181Y, of down to 16 mm2is inserted, no visible conductive material shall be exposed.BS 7856:2017 BRITISH STANDARD2 THE BRITISH STANDARDS INSTITUTION 2017 ALL RIGHTS
38、 RESERVEDTable 1 Dimensions and spacing of fixing holes and terminalsDimensions in mmLetter designationDimension ValueA A)Maximum overall height (measured from lower face of terminal block)209.6B Maximum overall width 158.8C Maximum overall projection (measured from front of meter board) 146.1D B)Ve
39、rtical distance between centre of top fixing hole and centreline of bottom fixing holes141.3 (max)E A)B)Vertical distance from centreline of bottom fixing holes to lower face of terminal block23.8 to 27.0F B)F)Distance between centres of bottom fixing holes to a vertical line which is central to the
40、 four main terminals51.6 to 53.2G B)F)From centrelines of current terminal holes 2 and 3 to a vertical line which is central to the four main terminals10.3 to 11.9H Height of terminal bosses (if present). The design of the meter can either incorporate cable entry bosses or be flat bottomed depending
41、 upon the manufacturers preference.0 to 5.0J B)F)From centrelines of current terminal holes 1 and 4 to a vertical line which is central to the four main terminals34.1 to 35.7K Size of aperture in current terminal to accept 8.0 mm diameter cable8.0 (min)L A)Length of parallel portion of cable apertur
42、e plus depth of any lead-in from lower face of terminal block28.5 (min)M From front of meter board to centreline of current terminal holes 17.4 to 20.7N Diameter of fixing holes 5.1 to 5.6P C)Terminal clamping screw flat-ended slightly chamfered, M6E)Q C)Length of standard pin to enter the current t
43、erminal hole 27.0 (max)W D)From centreline of bottom fixing holes to centreline of lower pinch screws12.5 to 15.0Y D)From centreline of lower pinch screws to centreline of upper pinch screws7.5 to 10.5NOTE The items applicable to single-phase, two-wire meters are shown in Figure 1.A)This measurement
44、 shall include the length of any terminal boss if present.B)For the purpose of estimating the tolerances, the datum line for the dimensions D, E, F, G, J should be: vertical datum: the vertical line which is central to the four main terminals.horizontal datum: centreline of bottom fixing holes. See
45、also note F)below.C)This dimension is not shown in Figure 1.D)Reference only applies to double screw fitted terminals.E)This screw should give a grip on any conductor from 10 mm2to 35 mm2.F)It should be noted that the vertical line central to the four main load terminals will not necessarily align w
46、ith the centreline of the meter. Such misalignment can occur with single phase 5 terminal meters. In such circumstances it is important to maintain the position of the lower fixing holes relative to the first four main terminals as the lower fixing holes are used to locate the first, second and four
47、th terminals on the test rig pin frames.BRITISH STANDARD BS 7856:2017 THE BRITISH STANDARDS INSTITUTION 2017 ALL RIGHTS RESERVED 3Figure 1 Spacing of fixing holes and terminals for single-phase, two-wire meterKey1 Datum Vertical 5 Base of meter case2 Meter back board 6 Side elevation3 Datum Horizont
48、al 7 Plan4 Front elevation 8 Top fixing hole if fittedNOTE Dimensions are given in Table 1.4.2 All conductors connected to the main and load terminals shall be clamped effectively and be capable of passing the test in accordance with Annex A. For a screw-fitted terminal, as indicated in Figure 1, th
49、ere shall be two screws in each terminal.NOTE However, other cable clamping arrangements are permissible.When tested in accordance with Annex A:a) all main and load terminals, irrespective of design and construction, shall resist the movement of any connected cable due to axial and/or rotational forces applied to the cables;BS 7856:2017 BRITISH STANDARD4 THE BRITISH STANDARDS INSTITUTION 2017 ALL RIGHTS RESERVEDb) all main and load terminals, irrespective of design and construction
