1、BRITISH STANDARD BS IEC 61888:2002 Nuclear power plants Instrumentation important to safety Determination and maintenance of trip setpoints ICS 27.120.20 BS IEC 61888:2002 This British Standard was published under the authority of the Standards Policy and Strategy Committee on 13 March 2003 BSI 13 M
2、arch 2003 ISBN 0 580 41387 X National foreword This British Standard reproduces verbatim IEC 61888:2002 and implements it as the UK national standard. The UK participation in its preparation was entrusted to Technical Committee NCE/8, Reactor instrumentation, which has the responsibility to: A list
3、of organizations represented on this committee can be obtained on request to its secretary. Cross-references The British Standards which implement international publications referred to in this document may be found in the BSI Catalogue under the section entitled “International Standards Corresponde
4、nce Index”, or by using the “Search” facility of the BSI Electronic Catalogue or of British Standards Online. This 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 does not of its
5、elf confer immunity from legal obligations. aid enquirers to understand the text; present to the responsible international/European committee any enquiries on the interpretation, or proposals for change, and keep the UK interests informed; monitor related international and European developments and
6、promulgate them in the UK. Summary of pages This document comprises a front cover, an inside front cover, the IEC title page, pages 2 to 20, an inside back cover an a back cover. The BSI copyright date displayed in this document indicates when the document was last issued. Amendments issued since pu
7、blication Amd. No. Date CommentsNORME INTERNATIONALE CEI IEC INTERNATIONAL STANDARD 61888 Premire dition First edition 2002-08 Centrales nuclaires de puissance Instrumentation importante pour la sret Dtermination et maintenance des points de consigne Nuclear power plants Instrumentation important to
8、 safety Determination and maintenance of trip setpoints Numro de rfrence Reference number CEI/IEC 61888:2002 BSIEC61888:200268818 IEC:0202 2 CONTENTS FOREWORD.3 INTRODUCTION.4 1 Scope.5 2 Normative references .5 3 Definitions 5 4 Abbreviations .8 5 Determination of setpoints8 5.1 Safety8 5.2 Safety
9、analysis8 5.3 Limiting safety system setting (LSSS)9 5.3.1 Channel uncertainty and trip setpoint.9 5.3.2 Channel uncertainty determination.12 5.3.3 Trip setpoint 12 5.3.4 Allowable value .12 5.4 Combination of uncertainties .13 5.4.1 Square-root-sum-of-squares method (SRSS).13 5.4.2 Algebraic method
10、.13 5.5 Operational considerations13 5.6 Instrument channel range13 6 Documentation .13 7 Maintenance of safety system setpoints .14 7.1 Testing14 7.2 Replacement .15 Annex A (informative) Example of setpoint determination.18 Bibliography20 Figure 1 Nuclear safety-related setpoint relationships16 Fi
11、gure 2 Process and measurement instrument uncertainties.17 Figure A.1 High reactor pressure setpoint relationships .19 BSIEC61888:2002268818 IEC:0202 3 INTERNATIONAL ELECTROTECHNICAL COMMISSION _ NUCLEAR POWER PLANTS INSTRUMENTATION IMPORTANT TO SAFETY DETERMINATION AND MAINTENANCE OF TRIP SETPOINTS
12、 FOREWORD 1) The IEC (International Electrotechnical Commission) is a worldwide organization for standardization comprising all national electrotechnical committees (IEC National Committees). The object of the IEC is to promote international co-operation on all questions concerning standardization i
13、n the electrical and electronic fields. To this end and in addition to other activities, the IEC publishes International Standards. Their preparation is entrusted to technical committees; any IEC National Committee interested in the subject dealt with may participate in this preparatory work. Intern
14、ational, governmental and non-governmental organizations liaising with the IEC also participate in this preparation. The IEC collaborates closely with the International Organization for Standardization (ISO) in accordance with conditions determined by agreement between the two organizations. 2) The
15、formal decisions or agreements of the IEC on technical matters express, as nearly as possible, an international consensus of opinion on the relevant subjects since each technical committee has representation from all interested National Committees. 3) The documents produced have the form of recommen
16、dations for international use and are published in the form of standards, technical specifications, technical reports or guides and they are accepted by the National Committees in that sense. 4) In order to promote international unification, IEC National Committees undertake to apply IEC Internation
17、al Standards transparently to the maximum extent possible in their national and regional standards. Any divergence between the IEC Standard and the corresponding national or regional standard shall be clearly indicated in the latter. 5) The IEC provides no marking procedure to indicate its approval
18、and cannot be rendered responsible for any equipment declared to be in conformity with one of its standards. 6) Attention is drawn to the possibility that some of the elements of this International Standard may be the subject of patent rights. The IEC shall not be held responsible for identifying an
19、y or all such patent rights. International Standard IEC 61888 has been prepared by subcommittee 45A: Reactor instrumentation, of IEC technical committee 45: Nuclear instrumentation. The text of this standard is based on the following documents: FDIS Report on voting 45A/444/FDIS 45A/464/RVD Full inf
20、ormation on the voting for the approval of this standard can be found in the report on voting indicated in the above table. This publication has been drafted in accordance with the ISO/IEC Directives, Part 3. Annex A is for information only. The committee has decided that the contents of this public
21、ation will remain unchanged until 2008. At this date, the publication will be reconfirmed; withdrawn; replaced by a revised edition, or amended. BSIEC61888:2002368818 IEC:0202 4 INTRODUCTION The purpose of this International Standard is to provide descriptions and recommendations on how to determine
22、 and maintain calculations for instrument setpoints associated with IEC 61513. This standard addresses known contributing errors in the channel from the process (including the primary element and sensor) through to and including the final setpoint device. This standard applies to the determination o
23、f setpoints used for automatic actions. The recommendations may also be used to determine indicator uncertainties for testing or operator decisions. In general, IAEA NS-R-1 and member country government regulations require that, where an important setpoint is specified for a variable on which a safe
24、ty limit has been placed, the setting is so chosen that automatic protective action will correct the most severe abnormal situation anticipated before a safety limit is exceeded. Inappropriate selection of a setpoint that does not leave a sufficient margin to account for instrument accuracy, the exp
25、ected environment, and minor calibration variations can result in failure to trip before a safety limit is exceeded. Protective instruments are provided with setpoints where specific actions are either initiated, terminated or prohibited. Setpoints must be maintained within prescribed limits as defi
26、ned by the operating licenses through periodic checks of the ability of the channel to perform its function. The single most prevalent reason for the drift of a setpoint out of compliance with a license requirement or technical specification has been the selection of a setpoint that does not allow a
27、 sufficient margin between the license or technical specification limit and the actual setting to account for instrument accuracy, the expected environment and minor calibration variations. In some cases, the setpoint selected was numerically equal to the license or technical specification limit and
28、 stated as an absolute value, thus leaving no apparent margin for uncertainties. In other cases, the setpoint was so close to the upper or lower limit of the instruments range that instrument drift placed the setpoint beyond the instruments range, thus nullifying the trip function. Other causes for
29、drift of a setpoint out of conformity with the license or technical specifications have been instrument design inadequacies and questionable calibration procedures. BSIEC61888:2002468818 IEC:0202 5 NUCLEAR POWER PLANTS INSTRUMENTATION IMPORTANT TO SAFETY DETERMINATION AND MAINTENANCE OF TRIP SETPOIN
30、TS 1 Scope This standard defines the requirements for assuring that automatic setpoints for nuclear safety system instrumentation (as defined in clause 3), are established and maintained within specified limits in nuclear power plants and nuclear reactor facilities. 2 Normative references The follow
31、ing referenced documents are indispensable for the application 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. IEC 60050-394:1995, International Electrotechnical Vocabula
32、ry (IEV) Chapter 394: Nuclear instrumentation: Instruments IEC 60671, Periodic testing and monitoring of the protective system of nuclear reactors IEC 61513:2001, Nuclear power plants Instrumentation and control for system important to safety General requirements for systems IAEA NS-R-1: 2000, Safet
33、y of nuclear power plants: Design 3 Definitions For the purposes of this document, the following terms and definitions apply. NOTE Additional definitions related to instrumentation terminology may be found in IEC 60050-394. 3.1 allowable value a limit value that the trip setpoint may have when teste
34、d periodically, beyond which appropriate action shall be taken 3.2 analytical limit (of setpoint) limit of a measured or calculated variable established by the safety analysis to ensure that a safety limit is not exceeded. The margin between the analytical limit (of the setpoint) and the safety limi
35、t allows to take into account: the response time of the instrument channel, the range of transients due to the considered accident. BSIEC61888:2002568818 IEC:0202 6 3.3 as found the condition in which a channel, or portion of a channel, is found after a period of operation and before recalibration (
36、if necessary) 3.4 as left the condition in which a channel, or portion of a channel, is left after calibration or final setpoint device setpoint verification 3.5 drift an undesired change in output over a period of time where change is unrelated to the input, environment, or load 3.6 error the algeb
37、raic difference between the indication and the ideal value of the measured signal 3.7 final setpoint device a component, or assembly of components, that provides input to the process voting logic for actuated equipment NOTE Examples of final setpoint devices are bistables, relays, pressure switches,
38、 and level switches. 3.8 foldover a device characteristic exhibited when a further change in the input produces an output signal that reverses its direction from the specified input-output relationship 3.9 independent uncertainty uncertainty components are independent of each other if their magnitud
39、es or algebraic signs are not significantly correlated 3.10 instrument channel an arrangement of components and modules, including sensor(s), as required to generate a single protective action signal when required by a plant condition 3.11 instrument channel range the region between the limits withi
40、n which a quantity is measured, received, or transmitted. Is expressed by stating the lower and upper instrument channel range values. 3.12 limiting safety system setting (LSSS) limiting safety system settings for nuclear reactors are settings for automatic protective devices related to those variab
41、les having significant safety functions 3.13 nuclear safety system instrumentation electronic and electrical equipment or instruments for ensuring the proper control and monitoring of a nuclear reactor, including all control and safety system instrumentation BSIEC61888:2002668818 IEC:0202 7 3.14 pri
42、mary element the system element that quantitatively converts the measured variable energy into a form suitable for measurement 3.15 random variable whose value at a particular future instant cannot be predicted exactly but can only be estimated by a probability distribution function 3.16 reference a
43、ccuracy number or quantity that defines a limit that errors will not exceed when a device is used under specified operating conditions 3.17 safety limit a limit on an important process variable, ,necessary to reasonably protect the integrity of physical barriers that guard against the uncontrolled r
44、elease of radioactivity 3.18 safety system system important to safety provided to ensure that in any condition, the safe shutdown of the reactor and the heat removal from the core and/or to limit the consequences of anticipated operational occurrences and design basis accident conditions (see IEC 61
45、513) 3.19 saturation device characteristic exhibited when a further change in the input signal produces no additional change, or progressively less change, in the output 3.20 sensor portion of a channel that responds to changes in a plant variable or condition and converts the measured process varia
46、ble into a signal, for example, electric or pneumatic 3.21 test interval elapsed time between the initiation (or successful completion) of tests on the same sensor, channel, load group, safety group, safety system, or other specified system or device 3.22 trip setpoint predetermined value for actuat
47、ion of the final setpoint device to initiate a protective action 3.23 channel uncertainty the amount to which an instrument channels output is in doubt (or the allowance made therefore) due to possible errors, either random or systematic, that have not been corrected. The channel uncertainty is gene
48、rally identified within a probability and confidence level. BSIEC61888:2002768818 IEC:0202 8 4 Abbreviations SRSS Square-Root-Sum-of-Squares CU Channel Uncertainty AL Analytical Limit TS Trip Setpoint LSSS Limiting Safety System Setting 5 Determination of setpoints Trip setpoints in nuclear safety s
49、ystem instruments shall be selected to provide sufficient allowance between the trip setpoint and the analytical limit to account for uncertainties. Detailed requirements for safety system instrument setpoint relationships are given in the following clauses, as illustrated in figure 1. The importance of the various types of safety system setpoints differ, and as such it may be appropriate to appl
