《BS-G-257-1-1998.pdf》由会员分享,可在线阅读,更多相关《BS-G-257-1-1998.pdf(56页珍藏版)》请在三一文库上搜索。
1、| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | BRITISH STANDARD AEROSPACE SERIES BS G 257
2、 : Part 1 : 1998 ICS 33.100; 49.060 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW Design of electromagnetic hazard protection of civil aircraft Part 1.Guide to theory and threats Licensed Copy: London South Bank University, London South Bank University, Sat Dec 09 01:44:32 G
3、MT+00:00 2006, Uncontrolled Copy, (c) BSI BS G 257 : Part 1 : 1998 This British Standard, having been prepared under the direction of the Engineering Sector Board, was published under the authority of the Standards Board and comes into effect on 15 March 1998 BSI 1998 The following BSI references re
4、late to the work on this standard: Committee reference ACE/66 Draft for comment 94/714808 DC ISBN 0 580 28984 2 Amendments issued since publication Amd. No.DateText affected Committees responsible for this British Standard The preparation of this British Standard was entrusted to Technical Committee
5、 ACE/66, Aerospace electromagnetic compatibility of aircraft, upon which the following bodies were represented: ERATechnology Ltd. Federation of the Electronics Industry Civil Aviation Authority (Airworthiness Division) Ministry of Defence Society of British Aerospace Companies Licensed Copy: London
6、 South Bank University, London South Bank University, Sat Dec 09 01:44:32 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS G 257 : Part 1 : 1998 BSI 1998i Contents Page Committees responsibleInside front cover Forewordiii 1Scope1 2Informative references1 3Definition1 4Background1 5Basic principles of E
7、MH protection design2 6EM hazards28 Table 1Current component36 Figures 1Magnetic field at a point distant from a current element3 2Interaction of magnetic field with conducting loop3 3The summation of magnetic field around a closed loop4 4Concept of displacement current5 5A wave in space6 6A wave f
8、(x, t) in time6 7A wave f (x, t) in space7 8A sinusoidally periodic wave8 9Exponential decay of signal with position8 10A standing wave9 11An EM wave propagating in the x-direction10 12The components of an elliptically polarized wave10 13A short dipole in cartesian co-ordinates11 14Antenna types13 1
9、5Wave propagation in three media15 16Plane wave incident on a cylinder16 17The current distribution on a cylindrical body16 18Current crowding at corners17 19Shielding effectiveness of spherical shells18 20Typical shield imperfections19 21Penetration through an aperture20 22Penetration through a low
10、 conductivity panel21 23The mechanism of shielding reduction by a penetrating conductor21 24A short circuit observed down a transmission line22 25An open circuit observed down a transmission line23 26The development of a dipole from an open-circuit transmission line23 27Current and field distributio
11、n in coaxial cable24 28H-field coupling and common-mode interference26 29Long-tailed pair with common-mode current rejection27 30Filter installation28 31Typical high-frequency equivalent circuit of a motor29 32Transformation of pulse into the frequency domain31 33Possible intersystem coupling paths3
12、2 34Model of a severe negative lightning flash current waveform33 Licensed Copy: London South Bank University, London South Bank University, Sat Dec 09 01:44:32 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS G 257 : Part 1 : 1998 ii BSI 1998 Page 35Model of a moderate positive lighting flash current
13、waveform33 36Intra- and inter-cloud, multiple burst current waveforms34 37Pre-strike electric field voltage waveforms38 38Current component A39 39Current component Ah40 40Current component B41 41Current component C42 42Current component D43 43Multiple stroke44 44External idealized current component
14、H45 45Double exponential current waveform 146 46Double exponential derivative voltage waveform 246 47Damped sinusoidal voltage/current waveform 347 48Double exponential voltage waveform 447 49Double exponential current waveform 548 List of referencesInside back cover Licensed Copy: London South Bank
15、 University, London South Bank University, Sat Dec 09 01:44:32 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS G 257 : Part 1 : 1998 BSI 1998iii Foreword BS G 257 : Parts 1 to 3, which have been prepared by Technical Committee ACE/66, constitute a design guide providing information to engineers involv
16、ed at all levels in the hardening of civil aircraft and their systems against electromagnetic hazards (EMHs). The design guide will be published in three Parts as follows: Part 1. Guide to electromagnetic theory and the electromagnetic threats posed to aircraft Part 2. Guide to protection Part 3. Gu
17、ide to clearance and testing This Part of BS G 257 provides background material on electromagnetic (EM) theory and the threats posed by EMH to aircraft and their systems. A detailed account of EM theory is not given, but enough of an insight is provided in order to understand the threats posed to th
18、e aircraft system, resulting effects and avoidance techniques described. This material is covered in the form of a qualitative description of electric, magnetic and EM fields, and the ways in which these interact with conducting bodies. In addition, the section contains discussion of the types and c
19、lassification of signals which can occur, and the way in which they relate to each other. In particular, it discusses the concepts of broadband and narrowband signals, balanced and unbalanced transmission, common- and differential-mode signal configuration, and the basic concepts of bandwidth and am
20、plitude limitation. The following Parts focus on the description of protection techniques and clearance and testing. Finally, this Part discusses all the threats and their interactions with the aircraft including continuous wave radio frequency (RF) fields, lightning and static electricity. Complian
21、ce with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front cover, an inside front cover, pages i to iv, pages 1 to 48, an inside back cover and a back cover. Licensed Copy: London South Bank University, London South Bank Uni
22、versity, Sat Dec 09 01:44:32 GMT+00:00 2006, Uncontrolled Copy, (c) BSI ivblank Licensed Copy: London South Bank University, London South Bank University, Sat Dec 09 01:44:32 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BSI 19981 BS G 257 : Part 1 : 1998 1 Scope This Part of BS G 257 has been written
23、to assist engineers working at all levels within companies involved in the aircraft industry. The guide does not contain mandatory requirements, but rather advice to assist in the solution of design problems. In order to meet the EMH protection needs of the customers specification, it is strongly re
24、commended that engineers consider the features discussed and use the suggestions made or provide an alternative solution for any problem. This guide does not discuss the following: a) the protection of the airframe against the structurally damaging, direct effects of lightning; b) the design of comm
25、unication systems in order to produce interference-free operation, since these aspects of RF systems design are covered in adequate detail in other documents; however, the problems of interaction between radio receivers and transmitters remain an important class of electromagnetic compatibility (EMC
26、) problem. 2 Informative references This Part of BS G 257 refers to other publications that provide information or guidance. Editions of these publications current at the time of issue of this standard are listed on the inside back cover, but reference should be made to the latest editions. 3 Defini
27、tion For the purposes of this Part of BS G 257, the following definition applies. electromagnetic compatibility (EMC) Situation in which an assembly of equipments or systems co-exist without mutual interference or damage and/or upset by the EM environment in which they are immersed. 4 Background 4.1
28、 The design of EMH protection for an electronic system should aim to ensure that the EM environment in which the system is immersed does not affect the normal operation of the system. In addition, the design should reduce the emissions of conducted or radiated EM energy from the system to a level wh
29、ich will not upset or damage the normal operation of other systems. Thus, the overall target of EMH protection should be to achieve EMC. 4.2 It was not until the early 1970s that aircraft made extensive use of electronic systems and thus EMH protection became a concern. In particular, systems affect
30、ing flight safety had become dependent on the reliable operation of an electronic system (e.g. fly-by-wire systems). Such widespread use of electronics necessitated the deliberate design of systems for EMC because the probability of interference had increased enormously, and the difficulty and expen
31、se of curing the likely problems was prohibitive. In addition, electronic technology had developed towards very compact, low-power, solid-state components utilizing low-level signalling and thus the susceptibility to electromagnetic interference (EMI) was increased. 4.3 From the early 1980s onwards,
32、 the extensive use of carbon fibre composite (CFC) in the airframe has significantly decreased the protection provided by the airframe to the electronic system from external EM threats of frequency content below 100 MHz. This has produced further design needs: the electrical design of the airframe s
33、hould be considered in order to provide the system with sufficient protection against the external EM environment and there should be minimum intersystem EM coupling. 4.4 Ensuring sufficient protection against EMHs for the complete aircraft has become a deliberate and complex design activity which s
34、hould include the electrical design of the airframe, the system installation and the design of the electronic equipment. A balanced protection strategy should ensure that the overall EMH protection needs of the aircraft are met within weight, volume and cost targets. 4.5 Achieving the EMC of aircraf
35、t systems is fraught with a number of problems, which include the high levels of EM threats, particularly the induced effects of lightning in the airframe, the proximity of the onboard transmitters (particularly the high-frequency (HF) transmitter) and the high cross-coupling between systems as a re
36、sult of the unavoidable proximity of systems. These EM threats have to be countered within the usual aerospace constraints of weight and volume. In addition, due regard should be taken of the extreme climatic and vibrational environment. 4.6 It is essential that designing for protection against EMHs
37、 should be considered from the very earliest stages of the airframe and system installation design. In order to achieve some control of the EMH protection design strategy throughout the aircraft design, development and production, a management strategy should be laid down at the very beginning. The
38、document describing this strategy is often called the EMC control plan. The control plan should highlight a visible design process for the design of the airframe and a complementary system installation design, which will result in only acceptable interference voltages and currents arriving at the eq
39、uipment connectors. The procurement of equipment with the required protection against EMH should be part of this plan and should be controlled via suitable specifications. Licensed Copy: London South Bank University, London South Bank University, Sat Dec 09 01:44:32 GMT+00:00 2006, Uncontrolled Copy
40、, (c) BSI 2 BSI 1998 BS G 257 : Part 1 : 1998 4.7 The safety of the aircraft is of paramount importance and those aspects of protection against EMH that could affect safety should rank equal with all the other design issues. The required performance of the aircraft will inevitably take precedence ov
41、er the EMH considerations, providing the EMH problem does not seriously affect that performance. It should be noted that consideration of the EMH protection design from the earliest concepts, and in conjunction with other aspects of design, is the only way to achieve optimum solutions in terms of we
42、ight, volume and cost. 5 Basic principles of EMH protection design NOTE. In 5.1 to 5.8, consideration is given to some of the more pertinent points of basic electromagnetics prior to discussing the subjects of intentional and unintentional EM radiation and the interaction of EM waves with conducting
43、 bodies. 5.1 EM theory The behaviour of EM fields is predictable and in broad terms, Maxwells equations and the basic laws of force field and flow, which will be described later, encompass the complete description of their behaviour. 5.2 The electric field 5.2.1 The mechanical force between two char
44、ges q1 and q2is proportional to the product of the charges and inversely proportional to the square of the distance between them, and acts along a line joining them. The force between charges or charged bodies leads to the concept of an electric field. This field produces a force on charges placed i
45、n it. If the charges are of the same polarity then the force is one of repulsion. Conversely, if the polarity of the charges is different then attraction occurs. Forces of this nature are encountered in many situations, such as the deflection of the electron beam by the field between the electrode p
46、lates in a cathode-ray tube, or the initial movement of free charges in a conductor on application of an electric field. 5.2.2 The magnitude of the electric field intensity E (in V/m) at a distance r (in m) from a charge q (in C) is given by Coulombs law: E =(1) q 4peoerr2 where eois the permittivit
47、y of free space (8.85 3 10212F/m); eris the relative permittivity of the medium in which the charges are placed (dimensionless). The product or(in F/m) is known as the permittivity of the medium. The electric field is thought of as having a flow or electric flux density (sometimes called displacemen
48、t) associated with it, in a similar way to voltage (potential difference) producing a flow of current. In this case, the electric field E (in V/m) and electric flux density D (in C/m2) at a point are related by: D = eE(2) where eis the permittivity of the medium (in F/m); Dis the displacement (in C/
49、m2); Eis the field strength (in V/m). 5.3 The magnetic field 5.3.1 A magnetic field may be described in a similar way to an electric field (see 5.2). However, unlike point charges, magnetic poles are not thought to exist as single poles in isolation; they always occur in pairs called magnetic dipoles. The manifestation of a magnetic field is therefore the rotational force or moment experienced by a magnetic dipole (electric fields can be treated analogously with regard to electric dipoles). The source of magnetic fields is electric current (at an atomic level in permanent magn
链接地址:https://www.31doc.com/p-3746022.html