1、Nuclear power plants Electrical power systems Electrical power systems analysisBS IEC 62855:2016BSI Standards PublicationWB11885_BSI_StandardCovs_2013_AW.indd 1 15/05/2013 15:06National forewordThis British Standard is the UK implementation of IEC 62855:2016.The UK participation in its preparation w
2、as entrusted to Technical Committee NCE/8, Instrumentation, Control any IEC National Committee interested in the subject dealt with may participate in this preparatory work. International, governmental and non-governmental organizations liaising with the IEC also participate in this preparation. IEC
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10、ation. 9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of patent rights. IEC shall not be held responsible for identifying any or all such patent rights. International Standard IEC 62855 has been prepared by subcommittee 45A: Instrumentat
11、ion, control and electrical systems of nuclear facilities, of IEC technical committee 45: Nuclear instrumentation. The text of this document is based on the following documents: FDIS Report on voting 45A/1094/FDIS 45A/1100/RVD Full information on the voting for the approval of this document can be f
12、ound in the report on voting indicated in the above table. This publication has been drafted in accordance with the ISO/IEC Directives, Part 2. BS IEC 62855:2016 6 IEC 62855:2016 IEC 2016 The committee has decided that the contents of this publication will remain unchanged until the stability date i
13、ndicated on the IEC web site under “http:/webstore.iec.ch“ in the data related to the specific publication. At this date, the publication will be reconfirmed, withdrawn, replaced by a revised edition, or amended. IMPORTANT The colour inside logo on the cover page of this publication indicates that i
14、t contains colours which are considered to be useful for the correct understanding of its contents. Users should therefore print this document using a colour printer. BS IEC 62855:2016IEC 62855:2016 IEC 2016 7 INTRODUCTION a) Technical background, main issues and organisation of the Standard The pri
15、ncipal function of the electrical power system is to support the safe operation of a nuclear power plant (NPP) in all modes of operation. A subset of the electrical power system is essential for supporting nuclear safety functions at various voltage levels. This subset is critical for all plant stat
16、es and events requiring plant cool-down in a controlled manner. A reliable power system is critical for maintaining control to power, control and monitor plant safety functions. This is required to support the barriers that prevent radiological releases during design basis accidents and design exten
17、sion conditions. International Standards and National safety codes provide guidance on acceptable requirements for safe and reliable operation of electrical distribution systems. Compliance with these safety codes and standards generally provides reasonable assurance for the correct electrical funct
18、ionality and capability of these systems in the nuclear power plant (NPP). The design basis of the electrical power systems in a NPP should be established by consideration of the following elements: nuclear design criteria, defence in depth approach, safety classification, design basis conditions (D
19、BC) and design extension conditions (DEC); requirements for transmission system operating limits, grid safety, grid code, plant performance and operating limits; architecture and specification of the electrical power systems; sizing of main components and systems such as unit auxiliary and standby t
20、ransformers, switchgear, cables, motors and standby alternating current (AC) and direct current (DC) power sources; load allocations and load power balance; load flow calculations; coordination of characteristics (voltage, current and short circuit current); support system requirements during postul
21、ated DBCs; design verification including verification analyses. An example of design bases considerations for electrical power systems is provided in informative Annex A. Guidelines and an example of analytical methods are detailed in informative Annex B. The relationship between analyses and verifi
22、cation of design bases and equipment specification is given in informative Annex C. An example of plant specific acceptance criteria (see 5.8) is given in informative Annex D. It is intended that the Standard will be used by operators of NPPs (utilities), systems evaluators and by licensors. b) Situ
23、ation of the current Standard in the structure of the IEC SC 45A standard series IEC 62855 is a third level IEC SC 45A document covering the topic of electrical power systems analysis. This standard supports the guidance provided in the IAEA Safety Guide SSG-34 related to the design of electrical po
24、wer systems for nuclear power plants. This standard is related to BS IEC 62855:2016 8 IEC 62855:2016 IEC 2016 IAEA Nuclear Energy Series NG-T-3.8 dealing with electric grid reliability and interface with nuclear power plants, and IEC 61513 establishing general requirement for I it covers power suppl
25、y systems including the supply systems of the I it adapts them and completes them to fit the nuclear context and coordinates with IEC 62443 (all parts). At level 2, regarding control rooms, IEC 60964 is the entry document for the IEC SC 45A control rooms standards, and IEC 62342 is the entry documen
26、t for the IEC SC 45A ageing management standards. NOTE 1 It is assumed that for the design of I power operation; shutting down; shutdown operation; outage; refuelling; maintenance; testing. 6) anticipated operational occurrences: unit trip/full-load rejection; loss of off-site power; loss of preferr
27、ed power supply. 7) design basis accidents 8) design extension conditions: station blackout; extended loss of AC power. c) The analyses for the off-site circuits capacity and capability should be performed in conjunction with the TSO. 5.3 Selection, verification and validation of analytical tools 5.
28、3.1 General A systematic approach should be adopted to ensure that the simulations accurately establish requirements determined from the preconditions and that the results can be validated independently by field measurements or other diverse and alternative methods. The scope of the study to be carr
29、ied out, the phenomena to be modelled and the complexity of the network to be analysed determine the type of software that should be used to perform the analyses. The software should have the capability to model asymmetric faults and conditions. The majority of commercially available software, devel
30、oped for power system analyses of large industrial complexes, will have the capability to simulate all the major buses and loads in a NPP and perform the minimum set of analyses identified by the designer. BS IEC 62855:2016 16 IEC 62855:2016 IEC 2016 This document does not recommend any specific sof
31、tware. 5.3.2 Recommendations The following recommendations apply. a) The following requirements should be considered for the specific software that will be used to establish the design basis of the electrical system. An auditable quality assurance process which complies with international standards
32、should be established and maintained. The software system should have been subject to a verification and validation (V the functional verification should be demonstrated through certification or the report of a QA audit. The documents used for functional validation should be fully referenced; the fu
33、nctional validation should allow the user to ensure that the equations correctly represent the physical phenomena studied in the defined operating range of the software tool; the functional V For transient stability, the main generator with its regulators (voltage and speed), the step-up transformer
34、, large motors and the network in the vicinity of the plant should be modelled in detail. The network in general may be modelled as an equivalent system for simplification based on technical justification. Assumptions made in the physical model used in the analysis should be clearly identified and v
35、alidated, and constraints identified. 5.5 Grid and NPP connection Analytical studies related to off-site power systems should be performed. The NPP design needs to take account of these analyses and evaluate the impact on the on-site power systems. The intent of these studies is to include all expec
36、ted power supply alignments and NPP operating scenarios to evaluate the off-site power supply design and operation in supporting safe operation of the NPP under all conditions. The studies should provide a comprehensive evaluation of off-site power source capability and capacity to meet the design r
37、equirements of the NPP. Additionally, the studies should be reviewed on a routine basis to assure that any changes in either on-site or off-site power systems are adequately evaluated for impact on the NPP power system. An analysis should be carried out to verify that maximum and minimum voltage and
38、 frequency deviations remain within the defined NPP design requirements. 5.6 Updating of system analyses Compliance with existing analyses should be confirmed or the analyses repeated when major replacements and/or major modifications of the electrical power system (on-site or off-site) are implemen
39、ted, and during licence renewal or periodic safety review. Motor starting studies should be performed as part of plant modifications including relocation of plant loads, and replacement of motors (which may have different operating characteristics) or generators. 5.7 Prerequisites for the performanc
40、e of electrical studies The following parameters should be established prior to the commencement of studies: preliminary ratings of electrical equipment; a power balance; all the operating modes of the NPP and the most onerous case identified. BS IEC 62855:2016 18 IEC 62855:2016 IEC 2016 In order to
41、 establish the most onerous operating conditions, different scenarios should be considered taking into account combinations of the following parameters: operation from on-site or off-site power sources; maximum and minimum short circuit power; maximum and minimum voltage range; maximum and minimum f
42、requency range; all operating modes of the NPP; maximum and minimum power generation of the NPP; maximum and minimum load taking account of all operating loads and environmental conditions; maximum and minimum electrical power system impedances; operating modes following single failures of electrica
43、l equipment; transfer of loads between power sources. 5.8 Acceptance requirements This document identifies the acceptance requirements. The acceptance criteria shall be derived from these requirements on a plant specific basis. Failure to meet the acceptance criteria shall be justified as not advers
44、ely impacting nuclear safety, or a design change shall be made. 6 Off-site power transient stability analyses 6.1 General Clause 6 applies to the grid and the main generator in the NPP. The recovery of a power transmission system subjected to a severe disturbance is of importance to reliable and saf
45、e operation of a NPP. The grid transient stability analyses should establish the limiting cases for the plant to ride through and remain connected to the grid for disturbances that do not result in the generator falling out of synchronism. These analyses should be performed in conjunction with the T
46、SO to establish parameters such as fault clearing time. 6.2 Recommendation Transient stability analyses should be performed to simulate power system operating conditions and establish the impact on the system stability. 6.3 Acceptance requirements The main generator shall remain connected to the gri
47、d and not fall out of synchronism on faults cleared by the TSOs protection scheme. The main generator shall fully comply with the TSO grid code requirements unless deviations are agreed with the TSO. The result of the analysis shall verify that the NPP on-site power system and connected loads can ri
48、de through transients in accordance with the TSO grid code requirements. 7 AC on-site power system analyses 7.1 General This clause applies to low and medium voltage AC power systems (not supplied by inverters or UPS) including standby AC power sources and alternate AC sources. BS IEC 62855:2016IEC
49、62855:2016 IEC 2016 19 7.2 Load flow studies 7.2.1 General Conducting a load flow study using multiple scenarios with different plant configurations and generation sources (see 5.7) provides assurance that the power system is adequately designed to meet the defined performance criteria. 7.2.2 Recommendations The following recommendations apply to load flow studies. a) Load flow studies for AC systems should be performed, simulating actual steady-state p
