BS-7674-1993 IEC-61225-1993.pdf
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1、BRITISH STANDARD BS 7674:1993 IEC 1225:1993 Nuclear power plants Instrumentation and control systems important for safety Requirements for electrical supplies Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 11:48:57 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS
2、7674:1993 This British Standard, having been prepared under the direction of the Nuclear Engineering Standards Policy Committee, was published under the authority of the Standards Board and comes into effect on 15 July 1993 BSI 08-1999 The following BSI references relate to the work on this standard
3、: Committee reference NCE/8 Draft for comment 91/77536 DC ISBN 0 580 21863 5 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Nuclear Engineering Standards Policy Committee (NCE/-) to Technical Committee NCE/8, upon which the following bo
4、dies were represented: AEA Technology British Aerospace plc British Nuclear Forum British Nuclear Fuels plc Electricity Association GAMBICA (BEAMA Ltd.) Health and Safety Executive Institution of Nuclear Engineers Amendments issued since publication Amd. No.DateComments Licensed Copy: London South B
5、ank University, London South Bank University, Fri Dec 08 11:48:57 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7674:1993 BSI 08-1999i Contents Page Committees responsibleInside front cover National forewordii 1Scope1 2Normative references1 3Definitions1 4System requirements1 5Requirements for indep
6、endence, physical separation and redundancy2 6Functional requirements for I an a.c. power system with internal batteries, supplying a.c. loads. Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 11:48:57 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7674:1993 2 BSI
7、 08-1999 The d.c. power system shall supply the d.c. loads, including control, monitoring, protection, switching and auxiliary power, during normal operation, anticipated operational occurrences and accident conditions. If loads important for safety require continuous a.c. power, a non-interruptible
8、 a.c. power system shall be provided to supply such loads. 4.2 System divisions The d.c. power system and the non-interruptible a.c. power system shall be divided into redundant and independent divisions in accordance with clause 5 of this standard. Each division of the d.c. power system shall consi
9、st of at least a battery supply, a battery charger and a distribution system (Figure 2). Each division of the non-interruptible a.c. power system shall consist of at least a supply from a d.c. power system, a d.c.-a.c. inverter and a distribution system. Another a.c. back-up power supply and an auto
10、matic switch-over device should also be provided (Figure 3 and Figure 4). 4.3 System boundaries The boundaries of the electrical supply system covered by this standard are from the incoming terminals of the breakers fed by the a.c. low-voltage power busbar of the Electrical Emergency Power Supplies
11、(Electrical EPS) up to the feeders dedicated to provide power to each individual load system, equipment and/or component (see Figure 1). For safety reasons, the loads will be divided into several separate divisions; each of these divisions shall be supplied from separate redundant supplies. Within t
12、he limits specified above, each system may include equipment such as transformers, converters, motor generator sets, inverters, cables, isolation devices, distribution boards, changeover devices, central and local batteries, switching, monitoring and protection equipment. Any equipment within an I t
13、he voltage control during loss of primary power supply shall maintain the output voltage within specified limits; the inverter shall be suitable for non-linear loads such as switched mode power supplies (SMPS) (see example 1 of Annex A); the frequency regulation; to facilitate rapid change-over, inv
14、erters should run synchronously with the dedicated back-up system when the system frequency is normal; the permissible output voltage and waveform quality (see clause 9). To supply electronic devices, intermediate circuit d.c./d.c. converters may be used. These d.c./d.c. converters will be connected
15、 on the input side at the voltage of the battery equipment and will feed, on the output side, loads or groups of loads with a controlled voltage which may have a nominal value different from the battery voltage. 7 Requirements for distribution system design The following requirements shall be consid
16、ered in relation to each system. 7.1 System aspects The supply system shall operate to maintain supplies important for safety under normal and relevant accident conditions. Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 11:48:57 GMT+00:00 2006, Uncontrolled Cop
17、y, (c) BSI BS 7674:1993 4 BSI 08-1999 The system design of the whole system shall accept redundant supplies and provide a continuous supply to each I the capacity of the supply system shall be adequate to support both the safety and the relevant non-safety loads for the time required by the safety c
18、riteria. 9 Characteristics of supplies given to individual loads 9.1 DC supplies The characteristics of the d.c. supplies required by individual loads shall have a margin on the values specified for the output of the power supply system to allow for deterioration in service, and for the impedance of
19、 connections between the load and the supply. Where d.c./a.c. inverters or d.c./d.c. converters are provided, the variation of the voltage at the equipment can be designed to be less than at the battery (see Annex A, example 3). Reference should be made to IEC 478. 9.2 AC supplies The characteristic
20、s of a.c. supplies required by individual loads shall have a margin on the values specified for the output of the power supply system to allow for deterioration in service and for the impedance of the connections between the load and the supply. Close control of the mean frequency may be required wh
21、en the frequency is used as a measure of time (e.g. on synchronous recorder charts). Examples of limits are given in Annex A. In case of three-phase supplies, the loads should be appropriately balanced across the three phases. Reference should be made to IEC 686. 10 Monitoring and protection Highly
22、reliable and continuously available power supplies for the I interruption in the supply; circuit breaker position; battery voltage; battery open circuit (e.g. by monitoring ripple in battery circuit current); battery charger or inverter failure; earth faults, etc. Alarms should be initiated in the e
23、vent of protective action, the loss of one supply in a redundant system or the loss of supply to a load. 10.2 Protection Protection shall be provided on the I&C supply system to minimize the effect on the system and the number of loads affected by a fault. The effect of spurious operation shall be m
24、inimized. The main source of faults will be in the loads and their connections to the supply, and so adequate individual instantaneous overload protection shall be provided, e.g. by fuses. The connection of supplies in parallel should be avoided and where permitted adequate protection shall be provi
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