天(tian)(tian)(tian)饋(kui)(kui)(kui)線連接的(de)(de)(de)是裝在發射(she)塔(ta)上的(de)(de)(de)發射(she)天(tian)(tian)(tian)線和處于機房(fang)內的(de)(de)(de)發射(she)機，由于天(tian)(tian)(tian)饋(kui)(kui)(kui)線不能埋地，雷擊發射(she)塔(ta)時會有近百萬(wan)伏(fu)的(de)(de)(de)高壓和數千(qian)安的(de)(de)(de)雷電流沿天(tian)(tian)(tian)饋(kui)(kui)(kui)線進入(ru)機房(fang)。因(yin)此(ci)，如何(he)預防(fang)沿天(tian)(tian)(tian)饋(kui)(kui)(kui)線入(ru)侵的(de)(de)(de)雷電流是防(fang)雷工程的(de)(de)(de)重要方面(mian)。今天(tian)(tian)(tian)，鈞(jun)和電子就該要點進行(xing)詳細的(de)(de)(de)分析(xi)：

措施一，在(zai)天(tian)饋線上(shang)安裝天(tian)饋浪涌保護器

常(chang)用(yong)的天饋(kui)線路防雷電流(liu)入侵的方法就是在發(fa)射(she)天線處或天饋(kui)線進入機(ji)房處安裝天線保護(hu)(hu)裝置，即天饋(kui)浪(lang)(lang)涌保護(hu)(hu)器。可根(gen)據被保護(hu)(hu)設備(bei)的頻(pin)率等參數，選擇(ze)插入損(sun)耗(hao)小、駐波比小的適配(pei)的天饋(kui)浪(lang)(lang)涌保護(hu)(hu)器。

當發(fa)射頻率較高（波長短(duan)）且(qie)為單(dan)一(yi)頻率時(shi)，低通濾波器可(ke)以簡化(hua)為一(yi)根長度為1/4波長的(de)導(dao)線，稱為1/4天饋(kui)浪(lang)涌保(bao)護(hu)器，這一(yi)導(dao)線對高頻發(fa)射信(xin)號來(lai)說(shuo)相當于開路，而對雷(lei)電波來(lai)說(shuo)相當于短(duan)接（這種天饋(kui)浪(lang)涌保(bao)護(hu)器只能限(xian)制出現在信(xin)號線間(jian)的(de)橫向(xiang)過電壓，不(bu)能限(xian)制雷(lei)擊時(shi)由于地(di)電位升高和接地(di)引(yin)下線壓降而造成的(de)縱(zong)向(xiang)過電壓）。

措施二，天饋線金屬外皮要重復接地

露天的天饋線沿塔身(shen)敷設(she)，金屬外皮的上下兩端就(jiu)近與鐵塔相連(lian)，并在機房入口處與接地(di)體(ti)再進行重復接地(di)，從而保證對雷電流(liu)有效分(fen)流(liu)。

措(cuo)施三，高通濾波器和低通濾波器組(zu)合將雷電流與(yu)通信分(fen)開(kai)

對雷(lei)(lei)電(dian)(dian)波的(de)(de)頻譜(pu)分(fen)析表(biao)明，雷(lei)(lei)電(dian)(dian)波的(de)(de)絕大(da)部(bu)分(fen)能量分(fen)布在(zai)幾(ji)十千(qian)赫(he)以下，而天線(xian)的(de)(de)發(fa)射頻率(lv)通(tong)(tong)(tong)(tong)(tong)常(chang)為數十兆赫(he)，微波通(tong)(tong)(tong)(tong)(tong)信(xin)的(de)(de)頻率(lv)則可達到千(qian)兆赫(he)。因此可以利用由(you)高通(tong)(tong)(tong)(tong)(tong)濾(lv)波器(qi)和低(di)通(tong)(tong)(tong)(tong)(tong)濾(lv)波器(qi)組合的(de)(de)電(dian)(dian)路將(jiang)雷(lei)(lei)電(dian)(dian)波通(tong)(tong)(tong)(tong)(tong)道(dao)和通(tong)(tong)(tong)(tong)(tong)信(xin)電(dian)(dian)磁(ci)波通(tong)(tong)(tong)(tong)(tong)道(dao)分(fen)開(kai)。在(zai)雷(lei)(lei)電(dian)(dian)波作用下高通(tong)(tong)(tong)(tong)(tong)濾(lv)波器(qi)開(kai)路，低(di)通(tong)(tong)(tong)(tong)(tong)濾(lv)波器(qi)導(dao)通(tong)(tong)(tong)(tong)(tong)將(jiang)雷(lei)(lei)電(dian)(dian)過(guo)電(dian)(dian)壓(ya)短接，使進入(ru)發(fa)射機的(de)(de)橫向過(guo)電(dian)(dian)壓(ya)得到限制(zhi)。在(zai)天線(xian)的(de)(de)工作頻率(lv)下，高通(tong)(tong)(tong)(tong)(tong)濾(lv)波器(qi)導(dao)通(tong)(tong)(tong)(tong)(tong)，低(di)通(tong)(tong)(tong)(tong)(tong)濾(lv)波器(qi)開(kai)路，保證了天線(xian)的(de)(de)正(zheng)常(chang)發(fa)射。

措施四(si)，發(fa)射機外殼與(yu)電纜外皮相連，并均壓

常用的(de)(de)防止縱向(xiang)過(guo)電(dian)(dian)壓(ya)危害(hai)的(de)(de)措施是將發(fa)(fa)射機(ji)外(wai)殼與電(dian)(dian)纜外(wai)皮相連，使發(fa)(fa)射機(ji)外(wai)殼的(de)(de)電(dian)(dian)位升高(gao)。但此(ci)時應注意加強發(fa)(fa)射機(ji)供(gong)電(dian)(dian)電(dian)(dian)源的(de)(de)防護，避免因電(dian)(dian)源處于低電(dian)(dian)位而引起電(dian)(dian)源的(de)(de)損壞。同(tong)時，加強發(fa)(fa)射機(ji)所處層面的(de)(de)均壓(ya)措施，避免在發(fa)(fa)射機(ji)和其(qi)他設備(bei)間形成電(dian)(dian)位差。

措施五，發射塔頂部安(an)裝避雷(lei)針，做好直擊雷(lei)防護

將(jiang)微(wei)波(bo)塔(ta)上同(tong)軸天饋線金屬外皮的(de)上端(duan)及下端(duan)分別就近與鐵塔(ta)相連，在(zai)機房(fang)入(ru)口處與接地體(ti)再連接一次等分流和均壓措(cuo)施并不能使(shi)縱向過(guo)電(dian)壓得到(dao)實質(zhi)性的(de)降(jiang)(jiang)(jiang)低(di)。降(jiang)(jiang)(jiang)低(di)縱向過(guo)電(dian)壓的(de)有效措(cuo)施是在(zai)微(wei)波(bo)塔(ta)頂部裝設限流型(xing)避雷針，大(da)幅(fu)度(du)降(jiang)(jiang)(jiang)低(di)雷擊微(wei)波(bo)塔(ta)時經(jing)發射(she)塔(ta)入(ru)地的(de)雷電(dian)流及發射(she)塔(ta)電(dian)位的(de)升高，從(cong)而(er)可使(shi)天饋線的(de)縱向過(guo)電(dian)壓得到(dao)大(da)幅(fu)度(du)降(jiang)(jiang)(jiang)低(di)。