【正文】 ences The British Standards which implement international or European publications referred to in this document may be found in the BSI Standards Catalogu e under the section entitled ―International Standards Correspondence Index‖, or by using the ―Find‖ facility of the BSI Standards Electronic Catalogue. 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. This British Standard, havin g been prepared under the direction of the Electro te c hnical Sector Comm itte e, was published under the authority of the Standards Committee and es into effect on 15 July 2020 169。 English version Functional safety of electrical/electronic/programmable electronic safetyrelated systems Part 7: Overview of techniques and measures (IEC 615087:2020) S233。lectriques/233。curit233。nahmen (IEC 615087:2020) This European Standard was approved by CENELEC on 20200703. CENELEC members are bound to ply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Uptodate lists and bibliographical references concerning such national standards may be obtained on application to the Central Secretariat or to any CENELEC member. This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CENELEC member into its own language and notified to the Central Secretariat has the same status as the official versions. CENELEC members are the national electrotechnical mittees of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom. CENELEC European Committee for Electrotechnical Standardization Comit233。r Elektrotechnische Normung Central Secretariat: rue de Stassart 35, B 1050 Brussels 169。 EN 50128 and prEN 50129). NOTE EN 50126 and EN 50128 were based on earlier drafts of IEC 61508. prEN 50129 is based on the principles of the latest version of IEC 61508. This list does not preclude other sector implementations of IEC 61508 which could be currently under development or published within IEC or CENELEC. Page 3 EN 61508?7:2020 Licensed Copy: Institute Of Technology Tallaght, Institute of Technology, Mon Jun 11 16:16:51 GMT+00:00 2007, Uncontrolled Copy, (c) BSI Endorsement notice The text of the International Standard IEC 615087:2020 was approved by CENELEC as a European Standard without any modification. In the official version, for Bibliography, the following notes have to be added for the standards indicated: IEC 600681 NOTE Harmonized as EN 600681:1994 (not modified). IEC 60529 NOTE Harmonized as EN 60523:1991 (not modified). IEC 60812 NOTE Harmonized as HD 485 S1:1987 (not modified). IEC 6100041 NOTE Harmonized as EN 6100041:1994 (not modified). IEC 6100045 NOTE Harmonized as EN 6100045:1995 (not modified). IEC 61025 NOTE Harmonized as HD 617 S1:1992 (not modified). IEC 610695 NOTE Harmonized as EN 610695:1995 (not modified). IEC 61078 NOTE Harmonized as EN 61078:1993 (not modified). IEC 611313 NOTE Harmonized as EN 611313:1993 (not modified). IEC 613461 NOTE Harmonized as EN 613461:1996 (not modified). Page 4 EN 61508?7:2020 Licensed Copy: Institute Of Technology Tallaght, Institute of Technology, Mon Jun 11 16:16:51 GMT+00:00 2007, Uncontrolled Copy, (c) BSI CONTENTS Page INTRODUCTION .............................................................................................................................. 10 Clause 1 Scope ........................................................................................................................ .................. 12 2 Normative references .................................................................................................................. 14 3 Definitions and abbreviations ................................................................................................ ...... 14 Annex A (informative) Overview of techniques and measures for E/E/PES: control of random hardware failures (see IEC 615082)................................................................................................ 15 Electrical............................................................................................................................ 15 Failure detection by online monitoring ................................................................. 15 Monitoring of relay contacts .................................................................................. 15 Comparator .......................................................................................................... . 15 Majority voter ........................................................................................................ 16 Idle current principle (deenergised to trip)............................................................ 16 Electronic .......................................................................................................................... 16 Tests by redundant hardware............................