ITU-T K25 光缆的防护.doc

Citccsj-3ITU-T Recommendation K.25Protection of optical fibre cables光缆的防护-(1996/2000)1 Scope and object第一章 范围和目标 The scope of this Recommendation is the protection against lightning of telecommunication lines in fibre optics installations.The object of this Recommendation is to limit the number of possible primary failures occurring in the optical fibre cable in a specified installation within values which are lower than or equal to the limit value, defined as the tolerable frequency of primary failures.Consequently, this Recommendation points out a method for both calculating the possible number of primary failures and choosing the feasible protective measures. Secondary failures are not considered in this Recommendation.本标准涉及范围是基于光纤装置的电信线路防雷保护光缆设计。本标准的目标是为了限制某一特定光纤装置中的光缆可能产生重大故障的次数，使其小于或等于规定的重大故障的次数，该值定义为一次故障容许频度。因此，本标准提出了计算一次故障可能次数和选择可行的保护措施的方法。二次故障不在本标准中考虑。2 References第二章 标准 The following Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision: all users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommendations is regularly published.以下文件中所包含的条款，通过本标准的引用，构成本标准的条款，对于注明日期的引用标准，任何一个版本的后续修订不适用于本版本。然而，鼓励本标准达成协议的各方考虑采用以下所示规范性文件的最新版本。1 CCITT Recommendation K.29 (1992), Coordinated protection schemes fortelecommunication cables below ground.K.29 地下通信电缆、光缆的综合保护方案。2 ITU-T Recommendation K.11 (1993), Principles of protection against overvoltages and overcurrents.K.11 过电压和过电流保护的原则3 ITU-T Recommendation K.39 (1996), Risk assessment of damages to telecommunication sites due to lightning dischargesK.39 电信局站雷电放电的危险评估3 Definitions第三章 定义 This Recommendation defines the following terms:本标准定义如下条款：3.1primary failures: Primary failures on the optical fibre cable are those which cause the interruption of service(breakage of one or more optical fibres), an unacceptable increase in attenuation of the optical fibre or an interruption in the remote power supply, if the equipment is powered by metallic conductors inside the optical cablePrimary failures are also those damages to the cable, such as destruction of the protective covering, moisture barrier, interconnecting elements and protective jelly, which, due to other mechanism acting on the damage, will lead to an unacceptable increase in attenuation of the optical fibre.3.1光缆上的一次故障是指业务中断（一根光纤或更多光纤的断裂），光纤的衰减增加到不可容许的数值或远供电源中断（如果设备由光缆内的金属导线供电，）等故障。一次故障也可能是光缆损坏的故障，比如防护层、防潮层、互连元件和保护填充胶的破裂等，这些源于其他机理的破坏，导致光缆性能的衰减增加到不可接受的程度。32secondary failures: Secondary failures on the optical fibre cable are those damages to the cable, such as the puncturing of the plastic protective covering (pin holing) and, in case, also of the metal sheath, which do not cause primary failures. 32二次故障是指那些不会产生一次故障的光缆损伤，如塑料外护层穿孔(针孔)以及有时产生的金属护套穿孔。33frequency of primary failures (Fp): Average annual number of expected primary failures in an optical fibre installation due to direct lightning flashes. 33一次故障频度(Fp) 直接雷造成光纤装置预期一次故障的年均次数。34risk of primary failures (Rd): Probable average annual loss of function in the optical fibre installation due to direct lightning flashes.34一次故障风险(Rd)直接雷造成光纤装置可能的年均功能损失。35tolerable frequency of primary failures (Fa): Average annual frequency of primary failures in an optical fibre installation not requiring additional protective measures.35一次故障容许频度(Fa) 无需采取附加保护措施，预期的由直接雷造成光纤装置的年均一次故障次数的最大值。36tolerable risk of primary failures (Ra): Maximum level of the risk of primary failures (Rd) due to direct lightning flashes not requiring additional protective measures.36容许的一次故障风险(Ra) 无需采取附加保护措施，由直接雷造成一次故障风险（Rd）的最大限值。37direct lightning flash: A lightning to aerial cable or to the ground surface within the equivalent arcing distance D from buried cable.37直接雷 雷击架空光缆，或雷击地表面与地埋光缆的距离小于等效电弧长度D。3.8direct lightning flash frequency (Nd): Expected average annual number of direct lightning flashes to an optical fibre installation3.8 直接雷频度(Nd)雷电直击光纤装置的预期年均次数。39equivalent arcing distance (D): Average distance from buried cable at which a lightning can arc to the cable.39等效电弧距离(D)引起光缆建弧时，雷击点和地埋光缆之间的平均距离。310failure lightning current (Ia): Minimum peak value of the lightning current giving rise to a direct arc on the cable and causing primary failures.310故障电流(Ia)引起与光缆直接建弧放电并导致一次故障的雷电流的最小峰值。311breakdown sheath current (Is): Current flowing in the metallic sheath which causes breakdown voltages between metallic elements inside the cable core and the metallic sheath.311屏蔽层击穿电流(Is)在光缆屏蔽层中流过，产生光缆芯内部金属加强芯与光缆金属屏蔽层间击穿电压，并导致一次故障的电流。312connection current (Ic): Minimum current flowing in the interconnecting elements that causes a primary failure due to thermal or mechanical effects.312连接电流(Ic)互相连接的元件导致一次故障的最小电流值，通过热能或机械效应来估计。313impulse current (Ip): Current to be used in the test for surge current resistibility of optical fibre cables. The test generator of this current is under consideration by IEC TC 81.313脉冲电流(Ip)测试光缆对浪涌电流.耐受能力时使用的电流。这种测试电流发生器目前IEC TC 81.在研究中（10/350s波形）。314interconnecting elements: Metallic elements connecting metallic sheath(s) or the metallic strength member(s) of optical fibre cable at joints and cable ends. 314互联元件在接头和光缆末端连接光缆金属屏蔽层或金属加强芯的金属元件。315test current (It): Minimum current injected by arc in the cable metallic sheath that causes a primary failure due to thermal or mechanical effects.315测试电流 光缆的金属屏蔽层建弧导致一次故障的最小电流，通过热能或机械效应来估计。316breakdown voltage (Ub): Impulse breakdown voltage between metallic components in the core and the metallic sheath of the optical cable.316击穿电压(Ub) 光缆芯内的金属加强芯与金属屏蔽层间的脉冲击穿电压。3.17damage correction factor (Kd): Factor which allows a conservative evaluation of the frequency of primary failures.3.17损坏修正系数(Kd) 允许保守估计一次故障次数的系数。3.18surge protective device (SPD): A device that is intended to limit transient over voltages and divert surge currents. It contains at least one non-linear component3.18浪涌保护器(SPD) 用于抑制瞬态过电压以及分流浪涌电流的装置，它至少包含一个非线型元件。3.19equipotential bonding bar (E.B.B.): An electrically conductive bar whose electric potential is used as common reference, and to which metallic parts within the installation can be bonded.3.19等电位连接排(E.B.B.) 用于公共电位基准（参考）的良导体排。金属装置，外部导体，电力和电信线路及其他光缆可以与之连接。3.20direct lightning current to aerial cables (J): Minimum lightning current which strikes an aerial cable causing a flashover to ground.3.20架空光缆直接雷电流(J) 雷击架空光缆导致对地闪络的雷电流的最小值。3.21exposed structure: A structure, e.g. telecommunication tower, high building, which needs to be protected against direct lightning strokes.3.21暴露建筑物诸如电信塔和高层建筑等（按IEC 61024-1-1的要求）需防直接雷的建筑物。322keraunic level or thunderstorm days (Td): Number of days per year in which thunder is heard in a given location322雷暴日(Td) 在给定的区域内每年听到的雷鸣的天数。（从年平均雷暴日数分布图获得的每年雷暴天数 IEC 61024-1-1）323ground flash density (Ng): Average number of lightning flashes to ground per square kilometre per year, concerning the region where the structure or the optical fibre cable is located.323地面落雷密度(Ng) 建筑物或光缆所在区域的平均每年每平方公里雷电对地闪络次数。324lightning collection area: Area of ground surface which has the same annual frequency of direct lightning as the structure or the line.324引雷范围 建筑物和线路有相同的每年直接雷次数的等效地表面区域。4 Reference configuration第四章参考结构Figure 1 represents the reference configuration for the optical fibre installations, where the connections with optical fibre cables between two Switches, between Switch and Line Termination and between Switch and line Equipment are shown图一为光纤装置的参考结构，表示了交换机之间，交换机和线路终端之间，以及交换机和线路设备之间的光缆连接。NOTE For the protection against lightning of the metallic cable installation between Equipment and Subscriber, the requirements requested by the Recommendation K.11 “Principles of protection against overvoltages and overcurrents” 5 shall be considered.注：设备和用户间防雷保护需要的光缆装置，见标准K.11“过电压和过电流保护的原则” 5 Figure 1/K.25 Reference configuration图1参考结构5Construction characteristics of the cable第五章 光缆的结构和特征This Recommendation applies to the following types of optical fibre cables:本标准适用于以下类型的光缆：type A: cable with dielectric core but having no metal elements (dielectric or metal-free cable);-类型A：采用电介质芯线，但无金属部分的光缆（电介质，或无金属光缆）。type B: cable with dielectric core and metal sheath or sheaths there are no metal elements in the core of the cable which has a metal sheath (for example the moisture barrier) or a metallic supporting wire -第二类型B：有一层或几层金属屏蔽层与电介质芯线的光缆：缆芯中没有金属成分，但是有金属屏蔽层（如防潮层）或金属支撑线。type C: cable with metal elements in the core and with a metal sheath or sheaths there are metal elements, such as conductors or strength members, in the core of the cable which has one or more metal sheaths;-类型C：有一层或几层金属屏蔽层,缆芯中也有金属芯线的光缆：缆芯中有金属成分，比如导线或金属加强芯。type D: cable with metal elements in the core and without a metal sheath-类型D：没有金属屏蔽层,但缆芯中也有金属芯线的光缆。For cable types B, C and D, the value of failure current (Ia) shall be evaluated, except for cables with more than one metal sheath.光缆类型B，C和D需要估算故障电流(Ia)的可能值5.2 Failure current for buried cable or aerial cable with earth connections of the metal sheath地埋或架空光缆金属屏蔽层与地连接的故障电流The failure current (Ia) is the lower value among the following values (see Figure 2):故障电流(Ia)是以下值中的较小者（见图2）- twice the connection current (Ic) evaluated with the test for surge current resistibility of the interconnecting elements (C.3);- 通过互联元件耐浪涌电流能力测试，估算两倍连接电流(Ic)。- the test current (It) evaluated with the test for surge current resistibility shown in C.4 for buried cables or C.5 for aerial cables (see Bibliography 2);- 通过C.4埋地光缆或C.5架空光缆介绍的光缆耐浪涌电流能力型测试，对不同类型的光缆估算测试电流(It)- for type C cables, twice the sheath breakdown current (Is) flowing in the cable metallic sheath (with or without an insulating covering). This current is calculated using the procedure of Annex B.- 对于类型C光缆，两倍的屏蔽层击穿电流(Is)在光缆屏蔽层中流过（采用或没有采用绝缘护层），电流的计算用规范性目录B的步骤。 Figure 2/K.25 Lightning currents in an optical fibre cable图2光缆中的雷电流Then则:Ia= It if It 2Is and It 2Is and Is 2Ic and Ic Is (3)5.3 Failure current for aerial cable without earth connections of the metal sheath金属屏蔽未接地的架空光缆的故障电流This type of cable is supposed to be installed in wood poles without ground wires nor shortly spaced guy wires. The failure current (Ia) for such a cable is the lower value among the following values (see Figure 2):这种类型的光缆假设已安装在无地线，也无短间距拉线的木杆上，对于这样的光缆，故障电流(Ia)是以下值中的较小者（见图2） twice the connection current (Ic) evaluated with the test for surge current resistibility of the interconnecting elements (C.3); 通过互联元件(C.3)耐浪涌电流能力测试，估算两倍连接电流(Ic)。 the test current (It) evaluated with the test for surge current resistibility shown in C.5 for aerial cables (see Bibliography 2);光缆耐浪涌电流能力型测试见C.5所示，对架空光缆估算测试电流(It) 见目录2 for type C cables, the direct lightning current (J) which strikes the aerial cable causing a flashover to ground. This current is calculated using the procedure of Annex B. 类型C的光缆， 雷击架空光缆导致对地闪络的直接雷电流（J）。这种电流用规范性目录B的程序。Then:则Ia =It if It J and It J and J 2Ic and 2Ic J (6)6 Need for protection第六章 防护需求The need for lightning protection of optical fibre installation depends on the frequency of primary failures (Fp) and its tolerable frequency of primary failures (Fa). The frequency of primary failures(Fp) is given by the following equation:光纤装置雷电防护的要求取决于一次故障频度(Fp)和一次故障容许频度(Fa)，一次故障频度(Fp)由下列方程给出：Fp= Fpb + Fpa + Fps (7)Where其中:Fpb is the frequency of primary failures to buried cablesFpb是地埋光缆的一次故障频度Fpa is the frequency of primary failures to aerial cablesFpa是架空光缆的一次故障频度Fps is the frequency of primary failures due to direct lightning strokes to exposed structures that the optical fibre cable entersFps是由雷电直击接入光缆的暴露建筑物，导致的一次故障频率。If the frequency of primary failures (Fp) is higher than the tolerable frequency of primary failures(Fa), protective measures are necessary to reduce Fp and minimize the risk of primary failures (Rd).如果一次故障频度高于一次故障容许频度(Fa)，需要采取保护措施来减少Fp，从而将一次故障风险降低到最小。The risk of primary failures is estimated with the following equation (see Appendix II):一次故障风险由下式估算（见附录II）：Rd = Fp (8)where is the relative amount of the expected losses per primary failure.其中每次一次鼓掌预期损失的相对量Therefore:因此Rd= Fpss + (Fpb + Fpa)d (9)Each Network Operator should define the tolerable frequency of primary failures (Fa) and the tolerable risk of primary failures (Ra). Values of Fa and Ra are suggested in Appendix II.每个网络操作员都应该定义容许的一次故障容许频度(Fa)和容许的一次故障风险(Ra)，典型Fa 和 Ra的值在附录II中给出。7 Protective measures第七章 防护措施 7.1 General概述The metallic elements of an optical fibre cable shall be continuous, i.e. it shall be connected across all splices, regenerators, etc., along the length of the cable. The metallic elements shall be connected to the equipotential bonding bar (E.B.B.) either directly or through a SPD, at the ends of the cable (see Figure 3)一条光缆中的金属部件沿光缆长度方向应保持连续，即所有接头及再生器处的金属部件应接通。光缆终端的金属部件应直接接至等电位连接排或通过一个浪涌保护器件(SPD) 接至等电位连接排（见图3）。 Figure 3/K.25 Example of metallic elements connection 图3金属部分连接的举例 If the E.B.B. of the subscriber building is not available, the metallic elements of the optical fibre cable shall be connected to a dedicated E.B.B. inside the optical network termination.如果用户建筑没有EBB，光缆的金属部分应该连接到光网络终端内一个指定的EBB上。For optical fibre cables with metallic elements, the following protective measures are usually considered:对于有金属芯线的光缆，下列常用防护措施可以一起考虑使用： use of dielectric or metal-free cables; 使用电介质或无金属光缆 choice of the cable type for both buried and aerial cables; 选择有较高故障电流值的地埋和架空光缆类型 use of the shield wires for buried cables; 仅对地埋光缆使用排流屏蔽线 earthing of the metal sheath along the route for aerial cables (see 5.2); 仅对沿架空光缆路径的金属屏蔽层接地（见5.2） route redundancy for both buried and aerial cables; 地埋和架空路径冗余 use of surge arresters for the protection of the metallic pairs of both buried and aerial cables使用避雷器对地埋和架空电缆的金属线对进行防护。NOTE 1 For the use of surge arresters on metallic pairs, see reference 2.注1：有关对金属线对使用SPD见参考2NOTE 2 Earthing of the metal sheath along the route for buried cables, having metal elements in the cable core, is not considered because the effectiveness of such protective measure is negligible on the reduction of the frequency of primary failures. 注2：沿地埋光缆路径没有考虑缆芯中有金属元件的金属屏蔽层接地，因为这种保护措施对减少一次故障的频度的作用可以忽略不计。NOTE 3 Cables leading to exposed structures may need to be protected by additional protective measures(see reference 3 and Bibliography 2).注3：根据ITU雷击手册连入暴露建筑的光缆需要附加防护措施以减少Fps（见参考3和目录2）7.2 Dielectric or metal-free cables电介质的或非金属光缆The use of dielectric or metal-free cables will prevent cable damage due to lightning.使用电介质的或非金属光缆可以防止光缆的雷击损害。NOTE 1 A non-metallic aerial cable is not directly susceptible to lightning damage. In fact, until now there has been no experience of such damage.注1： 非金属的架空光缆不易受直接雷击损害，事实上，至今还没有这种损害的例子。NOTE 2 For buried cables, the lowered resistance of the cable to moisture penetration and the difficulty of locating them during subsequent maintenance activities should be considered. Moreover metallic cables in the same ditch may be hit by direct lightning strikes and, as a consequence, the optical cable could also be destroyed (such damages are, until now, unknown). The same kind of problem may appear when a metal-free cable is accompanied by a metallic conductor (used to locate the optical cable).注2对于直埋光缆，需要考虑在后续维护中由于水分渗透降低光缆电阻以及进行定位的难度。另外，同一条沟中的金属光缆有可能被直接雷击中，因此，光纤也有可能被破坏（这种损害至今未知）。同样的问题也可能发生在那些靠近树木架设，或附近有定位光缆用的金属导体的非金属光缆上。7.3 Choice of cable characteristics for both buried and aerial installations地埋安装和架空安装对光缆特性的选择Each cable type has its own specific value of failure current (Ia) which is evaluated as indicated in clause 5. The choice of the cable type implies a specific value of failure current (Ia) and, the higher the value of Ia, the lower the frequency of primary failure, as can be calculated in Annex A.每种光缆有其自身特定的故障电流值(Ia)，由第五章节指定的方法计算，选择光缆暗含一个特定的电流(Ia)， Ia值越高，一次故障频度（Fp）值就越低，与附录A计算的一样。7.4 Use of shield wire for buried cables地埋光缆中屏蔽线的运用The probability of damage to buried cables can be reduced by the use of shield wires. Shield wires intercept a portion of the stroke current thus reducing the amount of current striking the cable. For properly installed shield wires, the shielding factor value, denoted by , implies that 100% of the stroke current flows on the cable sheath. Shield factor values can be calculated with the method shown in Appendix I.使用屏蔽线可以减少地埋光缆损害的可能性。屏蔽线截流一部分故障电流，这样可以减少雷击光缆的电流值。对于正确安装的屏蔽线，屏蔽系数值指雷击电流的100%流过光缆屏蔽层。屏蔽系数值的计算方法可以用附录I介绍的方法计算。Improvement to the frequency of primary failures (Fp) due to shield wires can be calculated as follows:Fp=NdPIa/ （10）屏蔽线对一次故障频率(Fp)的降低，可以按照下列公式计算：Fp=NdPIa/ （10）where:其中：Nd expected average annual number of direct lightning flashes to the cable; Nd是雷电直击光缆的预期年均次数。p probability for the lightning peak current to be equal to or higher than Ia/P是雷电流峰值等于或高于Ia/的概率。;Ia failure current Ia是故障电流; shielding factor是屏蔽系数. NOTE In the case of a metal f