1、BRITISH STANDARD BS 7767:1994 IEC 1117:1992 Method for Assessing the short-circuit withstand strength of partially type-tested assemblies (PTTA)BS7767:1994 This British Standard, having been prepared under the directionof the Power Electrical Engineering Standards Policy Committee, was published und
2、erthe authority of the Standards Board and comes intoeffect on 15 July 1994 BSI 07-1999 The following BSI references relate to the work on this standard: Committee reference PEL/12 Draft for comment 90/33360 DC ISBN 0 580 23199 2 Committees responsible for this British Standard The preparation of th
3、is British Standard was entrusted by the Power Electrical Engineering Standards Policy Committee (PEL/-) to Technical Committee PEL/12, upon which the following bodies were represented: ASTA Certification Services Association of British Mining Equipment Companies Building Employers Confederation Dep
4、artment of Trade and Industry (Consumer Safety Unit, CA Division) Electrical Installation Equipment Manufacturers Association (BEAMA Ltd.) ERA Technology Ltd. GAMBICA (BEAMA Ltd.) Health and Safety Executive Institution of Incorporated Executive Engineers National Inspection Council for Electrical I
5、nstallation Contracting National Quality Assurance Amendments issued since publication Amd. No. Date CommentsBS7767:1994 BSI 07-1999 i Contents Page Committees responsible Inside front cover National foreword ii Introduction 1 1 Scope 1 2 Reference documents 1 3 Definitions 1 4 Method of extrapolati
6、on 3 5 Conditions for application 3 Figure 1 Type-tested busbar structure (TS) 1 Figure 2 Non type-tested busbar structure (NTS) 2 Figure 3 Angular busbar configuration with supports at the corners 3 List of references Inside back coverBS7767:1994 ii BSI 07-1999 National foreword This British Standa
7、rd has been prepared under the direction of the Power Electrical Engineering Standards Policy Committee. It is identical with IEC1117:1992 A method for assessing the short-circuit withstand strength of partially type-tested assemblies (PTTA), published by the International Electrotechnical Commissio
8、n (IEC). The text of this standard was previously published as Amendment No. 1 to BS5486-1:1990 which has been withdrawn with the publication of BSEN 60439-1:1994. The following print types are used in this standard: requirement proper: in roman type; test specifications: in italic type; explanatory
9、 matter: in smaller roman type. Cross-references The Technical Committee has reviewed the provisions of IEC439-1:1985 1) , IEC865:1986 to which normative reference is made in the text, and has decided that they are acceptable for use in conjunction with this standard. There is no identical British S
10、tandard. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document c
11、omprises a front cover, an inside front cover, pages i and ii, pages1 to 4, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. 1) IEC 439-1:1985
12、has been superseded by IEC439-1:1992 which is identical with BSEN60439-1:1994.BS7767:1994 BSI 07-1999 1 Introduction The type test on a Type-tested Assembly (TTA) confirms the short-circuit withstand strength of all its parts. For a Partially Type-tested Assembly (PTTA) the verification of short-cir
13、cuit withstand strength shall be made either by test in accordance with 8.2.3.2.1 to 8.2.3.2.5 of IEC 439-1, or by extrapolation from similar type-tested arrangements, see8.2.3.2.6 of IEC439-1. Various methods of extrapolation can be conceived and are acceptable. The method described in this report
14、is one such method and may be used for partially type-tested assemblies to prove compliance with the requirements of7.5.1 of IEC439-1. 1 Scope This Technical Report describes an extrapolation method for assessing the short-circuit withstand strength of partially type-tested assemblies (PTTA). 2 Refe
15、rence documents IEC 439-1:1985, Low-voltage switchgear and controlgear assemblies Part 1: Requirements for type-tested and partially type-tested assemblies. IEC 865:1986, Calculation of the effects of short-circuit currents. 3 Definitions 3.1 type-tested busbar structure (TS) a structure whose arran
16、gement and equipment are documented by drawings, parts lists and descriptions in the test certificate (Figure 1) Figure 1 Type-tested busbar structure (TS)BS7767:1994 2 BSI 07-1999 3.2 non type-tested busbar structure (NTS) a structure which requires verification of short-circuit withstand strength
17、by means of extrapolation (Figure 2) Figure 2 Non type-tested busbar structure (NTS)BS7767:1994 BSI 07-1999 3 4 Method of extrapolation The short-circuit withstand strength of a derived structure, i.e.an NTS, is extrapolated from a type-tested structure (TS) by applying calculations according to IEC
18、865 to both structures. The short-circuit withstand strength of the NTS is considered verified if the calculations show that the NTS does not have to withstand higher mechanical stresses than the type-tested structure. 5 Conditions for application 5.1 General Changes of parameters, such as busbar cl
19、earances, busbar material, busbar cross-section and busbar configuration shown to be necessary by the calculation in conformity with IEC865 are permissible only in so far as the following conditions are adhered to. 5.2 Peak short-circuit current The short-circuit current may be changed only to lower
20、 values. 5.3 Thermal short-circuit strength The thermal short-circuit strength of an NTS may be verified by calculations according to IEC865. The calculated temperature rise of the NTS shall not be higher than that of the TS. 5.4 Busbar supports Changes of material or shape of supports taken from TT
21、As are not permitted. However, other supports may be used but they must have been previously type-tested for the required mechanical strength. 5.5 Busbar connections, equipment connections The type of busbar and equipment connections must have been previously type-tested. 5.6 Angular busbar configur
22、ations IEC 865 is applicable only to straight busbar configurations. Angular busbar configurations can be considered as a series of straight configurations when supports are provided at the corners (seeFigure 3). Figure 3 Angular busbar configuration with supports at the cornersBS7767:1994 4 BSI 07-
23、1999 5.7 Calculations with special regard to conductor oscillation For calculations in conformity with IEC865 on the tested structure (TS), the following values of the factors V B , V Bsand V Fare to be taken: V B= V Bs= V F= 1,0 V B is the ratio between dynamic and static main conductor stress V Bs
24、 is the ratio between dynamic and static sub-conductor stress V F is the ratio between dynamic and static force on support For the NTS, V B= V Bs= 1,0 and V Fis found from calculations in accordance with IEC865, but V F 1,0 is to be replaced by V F =1,0.BS7767:1994 BSI 07-1999 List of references See
25、 national foreword.BS 7767:1994 IEC 1117:1992 BSI 389 Chiswick High Road London W4 4AL BSIBritishStandardsInstitution BSI is the independent national body responsible for preparing BritishStandards. It presents the UK view on standards in Europe and at the international level. It is incorporated by
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