CATV系統防雷技術綜述

發布于：2014-8-15 19:50:30  點擊量：

CATV系統防雷技術綜述


雷(lei)(lei)(lei)是(shi)一(yi)種大氣中的(de)放(fang)電現(xian)象，常(chang)常(chang)使有(you)(you)線電視設備嚴重損壞，在CATV系(xi)統中，防(fang)雷(lei)(lei)(lei)設計是(shi)一(yi)項十分重要的(de)工(gong)作，而在實際(ji)工(gong)程當中，防(fang)雷(lei)(lei)(lei)并沒(mei)有(you)(you)引起技(ji)術人員的(de)足夠重視，一(yi)旦遭(zao)到(dao)雷(lei)(lei)(lei)擊，沒(mei)有(you)(you)良好(hao)防(fang)雷(lei)(lei)(lei)措(cuo)施(shi)的(de)系(xi)統就(jiu)會(hui)遭(zao)到(dao)嚴重破壞，甚至癱瘓(huan)。對于(yu)干線較長的(de)大系(xi)統，防(fang)雷(lei)(lei)(lei)設計更(geng)是(shi)刻不容(rong)緩的(de)大事(shi)，本文(wen)從(cong)雷(lei)(lei)(lei)擊的(de)產生機理以(yi)及雷(lei)(lei)(lei)電的(de)分布(bu)規律闡述(shu)雷(lei)(lei)(lei)電，以(yi)期讀者對雷(lei)(lei)(lei)擊有(you)(you)一(yi)個整(zheng)體的(de)認(ren)識，進而闡述(shu)防(fang)雷(lei)(lei)(lei)的(de)措(cuo)施(shi)以(yi)及CATV器材的(de)抗雷(lei)(lei)(lei)擊性能。

雷(lei)(lei)(lei)(lei)(lei)(lei)擊(ji)(ji)主(zhu)要(yao)有兩種：“直(zhi)擊(ji)(ji)雷(lei)(lei)(lei)(lei)(lei)(lei)”和“感應(ying)雷(lei)(lei)(lei)(lei)(lei)(lei)”。直(zhi)擊(ji)(ji)雷(lei)(lei)(lei)(lei)(lei)(lei)只有雷(lei)(lei)(lei)(lei)(lei)(lei)擊(ji)(ji)率(lv)的(de)(de)(de)(de)10%左右(you)，危(wei)害范(fan)圍一(yi)般較小，可(ke)使(shi)用避(bi)雷(lei)(lei)(lei)(lei)(lei)(lei)針(zhen)(zhen)、避(bi)雷(lei)(lei)(lei)(lei)(lei)(lei)線(xian)和避(bi)雷(lei)(lei)(lei)(lei)(lei)(lei)網來防(fang)避(bi)，危(wei)害大(da)得多的(de)(de)(de)(de)“感應(ying)雷(lei)(lei)(lei)(lei)(lei)(lei)”占雷(lei)(lei)(lei)(lei)(lei)(lei)擊(ji)(ji)率(lv)近(jin)90%，危(wei)害范(fan)圍甚(shen)(shen)(shen)廣，CATV系統(tong)的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)子設(she)備受(shou)(shou)雷(lei)(lei)(lei)(lei)(lei)(lei)擊(ji)(ji)損壞，主(zhu)要(yao)是(shi)(shi)(shi)感應(ying)雷(lei)(lei)(lei)(lei)(lei)(lei)造(zao)成(cheng)的(de)(de)(de)(de)。直(zhi)擊(ji)(ji)雷(lei)(lei)(lei)(lei)(lei)(lei)是(shi)(shi)(shi)帶(dai)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)云(yun)(yun)(yun)層和大(da)地(di)之間放(fang)(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)造(zao)成(cheng)的(de)(de)(de)(de)，在形成(cheng)雷(lei)(lei)(lei)(lei)(lei)(lei)云(yun)(yun)(yun)的(de)(de)(de)(de)過程(cheng)(cheng)中某些云(yun)(yun)(yun)積累起(qi)正電(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷(he)(he)的(de)(de)(de)(de)靂云(yun)(yun)(yun)接近(jin)到一(yi)定程(cheng)(cheng)度時，發生訊猛(meng)的(de)(de)(de)(de)放(fang)(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)。出現耀眼的(de)(de)(de)(de)閃光(guang)。當雷(lei)(lei)(lei)(lei)(lei)(lei)云(yun)(yun)(yun)很低(di)，周圍又沒(mei)有異性電(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷(he)(he)的(de)(de)(de)(de)雷(lei)(lei)(lei)(lei)(lei)(lei)云(yun)(yun)(yun)時，就會在地(di)面或者建筑(zhu)物上感應(ying)出異性電(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷(he)(he)，形成(cheng)帶(dai)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)云(yun)(yun)(yun)層向地(di)面或者建筑(zhu)物放(fang)(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)；放(fang)(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流可(ke)達到幾十(shi)甚(shen)(shen)(shen)至幾百千安(an)，放(fang)(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)時間為50－100µ S，這(zhe)種放(fang)(fang)(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)就是(shi)(shi)(shi)直(zhi)擊(ji)(ji)雷(lei)(lei)(lei)(lei)(lei)(lei)，直(zhi)擊(ji)(ji)雷(lei)(lei)(lei)(lei)(lei)(lei)對建筑(zhu)物和人(ren)、畜安(an)全危(wei)害甚(shen)(shen)(shen)大(da)。安(an)裝于避(bi)雷(lei)(lei)(lei)(lei)(lei)(lei)針(zhen)(zhen)后(hou)，CATV系統(tong)的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)子設(she)備即使(shi)在其保護(hu)范(fan)圍之內，仍然可(ke)能遭雷(lei)(lei)(lei)(lei)(lei)(lei)擊(ji)(ji)而(er)受(shou)(shou)損，大(da)多數(shu)都是(shi)(shi)(shi)燒保險絲，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源變壓器(qi)，整流元件，三端穩(wen)壓器(qi)，嚴(yan)重(zhong)的(de)(de)(de)(de)還可(ke)能損壞集(ji)成(cheng)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)路等(deng)元件，這(zhe)說明雷(lei)(lei)(lei)(lei)(lei)(lei)擊(ji)(ji)不是(shi)(shi)(shi)從(cong)(cong)天線(xian)引(yin)入的(de)(de)(de)(de)，而(er)是(shi)(shi)(shi)從(cong)(cong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)源線(xian)引(yin)入的(de)(de)(de)(de)，可(ke)見(jian)避(bi)雷(lei)(lei)(lei)(lei)(lei)(lei)針(zhen)(zhen)雖(sui)保護(hu)了建筑(zhu)物，卻保護(hu)不了置于其內的(de)(de)(de)(de)CATV電(dian)(dian)(dian)(dian)(dian)(dian)(dian)子設(she)備，這(zhe)是(shi)(shi)(shi)感應(ying)雷(lei)(lei)(lei)(lei)(lei)(lei)造(zao)成(cheng)的(de)(de)(de)(de)。

感(gan)(gan)(gan)(gan)應(ying)(ying)雷(lei)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)靜電(dian)(dian)(dian)(dian)(dian)(dian)(dian)感(gan)(gan)(gan)(gan)應(ying)(ying)和(he)雷(lei)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)產生(sheng)的(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)磁(ci)感(gan)(gan)(gan)(gan)應(ying)(ying)兩(liang)種原因(yin)所(suo)引(yin)起(qi)的(de)，當(dang)帶電(dian)(dian)(dian)(dian)(dian)(dian)(dian)的(de)云(yun)層（雷(lei)云(yun)）靠近(jin)輸電(dian)(dian)(dian)(dian)(dian)(dian)(dian)線(xian)(xian)路時(shi)，會(hui)在它們上(shang)面感(gan)(gan)(gan)(gan)應(ying)(ying)出(chu)異性電(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷(he)(he)(he)，這(zhe)些(xie)異性電(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷(he)(he)(he)被雷(lei)云(yun)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷(he)(he)(he)束縛著。當(dang)雷(lei)云(yun)對附(fu)近(jin)的(de)目標(biao)或接閃器(qi)（避(bi)雷(lei)針是最早(zao)、最常用的(de)接閃器(qi)）放電(dian)(dian)(dian)(dian)(dian)(dian)(dian)時(shi)，其電(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷(he)(he)(he)迅速(su)中(zhong)和(he)，而(er)輸電(dian)(dian)(dian)(dian)(dian)(dian)(dian)線(xian)(xian)路上(shang)束縛的(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷(he)(he)(he)便(bian)為自由電(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷(he)(he)(he)，形成(cheng)局(ju)部感(gan)(gan)(gan)(gan)應(ying)(ying)高(gao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)位。這(zhe)種感(gan)(gan)(gan)(gan)應(ying)(ying)高(gao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)位發(fa)生(sheng)在低(di)壓(ya)架空線(xian)(xian)路時(shi)亦可(ke)達100KV；在電(dian)(dian)(dian)(dian)(dian)(dian)(dian)信(xin)線(xian)(xian)路上(shang)可(ke)達40－60KV。而(er)且它可(ke)以沿著線(xian)(xian)路傳入電(dian)(dian)(dian)(dian)(dian)(dian)(dian)子設(she)備，造成(cheng)損害。雷(lei)擊后巨大(da)的(de)雷(lei)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)在周圍空間產生(sheng)交變(bian)磁(ci)場，由于電(dian)(dian)(dian)(dian)(dian)(dian)(dian)磁(ci)感(gan)(gan)(gan)(gan)應(ying)(ying)使附(fu)近(jin)設(she)備感(gan)(gan)(gan)(gan)應(ying)(ying)出(chu)高(gao)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓(ya)，從而(er)使設(she)備損壞。

對于系統的(de)(de)防(fang)(fang)雷(lei)(lei)(lei)(lei)(lei)(lei)最有利的(de)(de)措施是(shi)系統有良(liang)(liang)好(hao)的(de)(de)接(jie)地，良(liang)(liang)好(hao)接(jie)地不(bu)僅能及(ji)早的(de)(de)泄(xie)(xie)掉感(gan)應雷(lei)(lei)(lei)(lei)(lei)(lei)產生的(de)(de)電(dian)(dian)(dian)壓(ya)，同(tong)時(shi)(shi)(shi)也可泄(xie)(xie)掉由(you)于設備漏電(dian)(dian)(dian)而產生的(de)(de)對地電(dian)(dian)(dian)壓(ya)，達到保護設備和人身安全的(de)(de)目的(de)(de)，具體的(de)(de)系統防(fang)(fang)雷(lei)(lei)(lei)(lei)(lei)(lei)也是(shi)從接(jie)地開(kai)始的(de)(de)。與此同(tong)時(shi)(shi)(shi)，在需(xu)要(yao)的(de)(de)地方按裝避(bi)(bi)(bi)(bi)(bi)(bi)雷(lei)(lei)(lei)(lei)(lei)(lei)外、避(bi)(bi)(bi)(bi)(bi)(bi)雷(lei)(lei)(lei)(lei)(lei)(lei)器(qi)(qi)(qi)(qi)，但是(shi)選用(yong)器(qi)(qi)(qi)(qi)材的(de)(de)抗雷(lei)(lei)(lei)(lei)(lei)(lei)擊性(xing)能也不(bu)忽視(shi)，在選用(yong)器(qi)(qi)(qi)(qi)材時(shi)(shi)(shi)，考查器(qi)(qi)(qi)(qi)材的(de)(de)抗雷(lei)(lei)(lei)(lei)(lei)(lei)擊性(xing)能也是(shi)重(zhong)要(yao)的(de)(de)一環。目前，我(wo)國大(da)量(liang)生產和使用(yong)避(bi)(bi)(bi)(bi)(bi)(bi)雷(lei)(lei)(lei)(lei)(lei)(lei)器(qi)(qi)(qi)(qi)，有以電(dian)(dian)(dian)工碳(tan)化(hua)硅閥(fa)片為(wei)(wei)基(ji)本(ben)元(yuan)件的(de)(de)各(ge)種閥(fa)式(shi)避(bi)(bi)(bi)(bi)(bi)(bi)雷(lei)(lei)(lei)(lei)(lei)(lei)器(qi)(qi)(qi)(qi)；有以氧(yang)(yang)化(hua)鋅閥(fa)片為(wei)(wei)基(ji)本(ben)元(yuan)件的(de)(de)氧(yang)(yang)化(hua)鋅避(bi)(bi)(bi)(bi)(bi)(bi)雷(lei)(lei)(lei)(lei)(lei)(lei)器(qi)(qi)(qi)(qi)，氧(yang)(yang)化(hua)鋅避(bi)(bi)(bi)(bi)(bi)(bi)雷(lei)(lei)(lei)(lei)(lei)(lei)器(qi)(qi)(qi)(qi)較之閥(fa)式(shi)避(bi)(bi)(bi)(bi)(bi)(bi)雷(lei)(lei)(lei)(lei)(lei)(lei)器(qi)(qi)(qi)(qi)具有動作迅速、通流(liu)容量(liang)大(da)、殘壓(ya)低(di)、無續流(liu)、結構簡(jian)單(dan)、可靠性(xing)高(gao)、壽命長、維護簡(jian)便(bian)等(deng)優(you)點。下(xia)面重(zhong)點講述氧(yang)(yang)化(hua)鋅避(bi)(bi)(bi)(bi)(bi)(bi)雷(lei)(lei)(lei)(lei)(lei)(lei)器(qi)(qi)(qi)(qi)，氧(yang)(yang)化(hua)鋅壓(ya)敏避(bi)(bi)(bi)(bi)(bi)(bi)雷(lei)(lei)(lei)(lei)(lei)(lei)器(qi)(qi)(qi)(qi)對感(gan)應雷(lei)(lei)(lei)(lei)(lei)(lei)及(ji)雷(lei)(lei)(lei)(lei)(lei)(lei)電(dian)(dian)(dian)波入(ru)侵的(de)(de)防(fang)(fang)止是(shi)有效的(de)(de)。其工作原理是(shi)其伏安特性(xing)的(de)(de)非線性(xing)。正常(chang)電(dian)(dian)(dian)壓(ya)時(shi)(shi)(shi)，避(bi)(bi)(bi)(bi)(bi)(bi)雷(lei)(lei)(lei)(lei)(lei)(lei)器(qi)(qi)(qi)(qi)呈高(gao)阻狀(zhuang)(zhuang)態，只有很(hen)小(xiao)的(de)(de)泄(xie)(xie)漏電(dian)(dian)(dian)流(liu)（µA數(shu)(shu)量(liang)級），功率損耗很(hen)小(xiao)，當(dang)線路中出現過壓(ya)時(shi)(shi)(shi)，避(bi)(bi)(bi)(bi)(bi)(bi)雷(lei)(lei)(lei)(lei)(lei)(lei)器(qi)(qi)(qi)(qi)呈低(di)阻狀(zhuang)(zhuang)態（時(shi)(shi)(shi)間效應為(wei)(wei)10-9數(shu)(shu)量(liang)級）過電(dian)(dian)(dian)壓(ya)以放(fang)電(dian)(dian)(dian)電(dian)(dian)(dian)流(liu)的(de)(de)形式(shi)通過避(bi)(bi)(bi)(bi)(bi)(bi)雷(lei)(lei)(lei)(lei)(lei)(lei)器(qi)(qi)(qi)(qi)流(liu)入(ru)大(da)地，過電(dian)(dian)(dian)壓(ya)被抑制下(xia)來，浪涌電(dian)(dian)(dian)壓(ya)過后，線路電(dian)(dian)(dian)壓(ya)恢復正常(chang)時(shi)(shi)(shi)，避(bi)(bi)(bi)(bi)(bi)(bi)雷(lei)(lei)(lei)(lei)(lei)(lei)器(qi)(qi)(qi)(qi)又(you)呈高(gao)阻絕緣(yuan)狀(zhuang)(zhuang)態，因(yin)此避(bi)(bi)(bi)(bi)(bi)(bi)雷(lei)(lei)(lei)(lei)(lei)(lei)器(qi)(qi)(qi)(qi)必須有良(liang)(liang)好(hao)的(de)(de)接(jie)地裝置與之配(pei)合。

雷(lei)(lei)電(dian)(dian)過(guo)電(dian)(dian)壓(ya)的(de)(de)(de)(de)電(dian)(dian)流(liu)是(shi)一種很快上升(sheng)到(dao)峰(feng)(feng)值，然后較慢下(xia)降的(de)(de)(de)(de)脈沖(chong)，其時(shi)間量(liang)(liang)值為10-6S數量(liang)(liang)級(ji)，國家的(de)(de)(de)(de)通(tong)用標(biao)準(zhun)是(shi)8／20µS，即用8µS的(de)(de)(de)(de)時(shi)間上升(sheng)到(dao)峰(feng)(feng)值，然后用20µS的(de)(de)(de)(de)時(shi)間下(xia)降到(dao)半峰(feng)(feng)值，而(er)(er)(er)氧(yang)化鋅避雷(lei)(lei)器(qi)的(de)(de)(de)(de)響應時(shi)間為10-9數量(liang)(liang)級(ji)，因而(er)(er)(er)響應時(shi)間是(shi)來得及(ji)的(de)(de)(de)(de)，其次是(shi)幅值問題(ti)，有線電(dian)(dian)視(shi)的(de)(de)(de)(de)供(gong)電(dian)(dian)電(dian)(dian)源經過(guo)電(dian)(dian)力(li)系統(tong)的(de)(de)(de)(de)多級(ji)避雷(lei)(lei)，因而(er)(er)(er)雷(lei)(lei)電(dian)(dian)脈沖(chong)電(dian)(dian)流(liu)大于 5 KA的(de)(de)(de)(de)概(gai)率不會(hui)大干15%，只要(yao)選擇(ze)通(tong)流(liu)容量(liang)(liang)為5 KA的(de)(de)(de)(de)避雷(lei)(lei)器(qi)，其殘壓(ya)也是(shi)設備能(neng)夠(gou)承受的(de)(de)(de)(de)，加(jia)上合(he)乎要(yao)求的(de)(de)(de)(de)接地就會(hui)達到(dao)避雷(lei)(lei)的(de)(de)(de)(de)效果。

1．無(wu)線(xian)(xian)(xian)(xian)的(de)(de)(de)(de)(de)(de)防(fang)(fang)雷(lei)(lei)接(jie)(jie)地(di)(di)。有(you)(you)線(xian)(xian)(xian)(xian)電(dian)視的(de)(de)(de)(de)(de)(de)接(jie)(jie)收天(tian)(tian)(tian)線(xian)(xian)(xian)(xian)和(he)豎桿一般架(jia)設(she)在建(jian)筑物(wu)(wu)(wu)的(de)(de)(de)(de)(de)(de)頂端(duan)，應(ying)(ying)(ying)(ying)(ying)把所有(you)(you)的(de)(de)(de)(de)(de)(de)接(jie)(jie)收天(tian)(tian)(tian)線(xian)(xian)(xian)(xian)，包括衛星接(jie)(jie)收無(wu)線(xian)(xian)(xian)(xian)的(de)(de)(de)(de)(de)(de)接(jie)(jie)地(di)(di)焊(han)在一起，接(jie)(jie)天(tian)(tian)(tian)線(xian)(xian)(xian)(xian)的(de)(de)(de)(de)(de)(de)豎桿（架(jia)）上應(ying)(ying)(ying)(ying)(ying)裝(zhuang)設(she)避(bi)(bi)雷(lei)(lei)針(zhen)(zhen)(zhen)，避(bi)(bi)雷(lei)(lei)針(zhen)(zhen)(zhen)的(de)(de)(de)(de)(de)(de)高(gao)度應(ying)(ying)(ying)(ying)(ying)能滿(man)足對天(tian)(tian)(tian)線(xian)(xian)(xian)(xian)設(she)施的(de)(de)(de)(de)(de)(de)保(bao)(bao)護(hu)，安裝(zhuang)獨立的(de)(de)(de)(de)(de)(de)避(bi)(bi)雷(lei)(lei)鐘時，由于單(dan)根避(bi)(bi)雷(lei)(lei)針(zhen)(zhen)(zhen)的(de)(de)(de)(de)(de)(de)保(bao)(bao)護(hu)范圍呈帳篷(peng)狀，邊(bian)界線(xian)(xian)(xian)(xian)呈雙(shuang)曲線(xian)(xian)(xian)(xian)，所以避(bi)(bi)雷(lei)(lei)外(wai)高(gao)于天(tian)(tian)(tian)線(xian)(xian)(xian)(xian)頂端(duan)的(de)(de)(de)(de)(de)(de)長度應(ying)(ying)(ying)(ying)(ying)大于天(tian)(tian)(tian)線(xian)(xian)(xian)(xian)的(de)(de)(de)(de)(de)(de)最大尺寸(cun)，避(bi)(bi)雷(lei)(lei)針(zhen)(zhen)(zhen)與(yu)天(tian)(tian)(tian)線(xian)(xian)(xian)(xian)之間(jian)的(de)(de)(de)(de)(de)(de)最小(xiao)(xiao)水平間(jian)距(ju)應(ying)(ying)(ying)(ying)(ying)大于3M，建(jian)筑物(wu)(wu)(wu)已有(you)(you)防(fang)(fang)雷(lei)(lei)接(jie)(jie)地(di)(di)系統(tong)時避(bi)(bi)雷(lei)(lei)針(zhen)(zhen)(zhen)和(he)天(tian)(tian)(tian)線(xian)(xian)(xian)(xian)豎桿的(de)(de)(de)(de)(de)(de)接(jie)(jie)地(di)(di)應(ying)(ying)(ying)(ying)(ying)與(yu)建(jian)筑物(wu)(wu)(wu)的(de)(de)(de)(de)(de)(de)防(fang)(fang)雷(lei)(lei)接(jie)(jie)地(di)(di)系統(tong)共地(di)(di)連接(jie)(jie)；建(jian)筑物(wu)(wu)(wu)無(wu)專(zhuan)門的(de)(de)(de)(de)(de)(de)防(fang)(fang)雷(lei)(lei)接(jie)(jie)地(di)(di)可利用(yong)(yong)時，應(ying)(ying)(ying)(ying)(ying)設(she)置專(zhuan)門的(de)(de)(de)(de)(de)(de)接(jie)(jie)地(di)(di)裝(zhuang)置，從(cong)(cong)接(jie)(jie)閃器至接(jie)(jie)地(di)(di)裝(zhuang)置采用(yong)(yong)兩(liang)根引(yin)下(xia)線(xian)(xian)(xian)(xian)，從(cong)(cong)不(bu)同的(de)(de)(de)(de)(de)(de)方位以最短的(de)(de)(de)(de)(de)(de)距(ju)離沿建(jian)筑物(wu)(wu)(wu)引(yin)下(xia)，其(qi)接(jie)(jie)地(di)(di)電(dian)阻(zu)應(ying)(ying)(ying)(ying)(ying)小(xiao)(xiao)于4歐(ou)姆，無(wu)論是新(xin)制作的(de)(de)(de)(de)(de)(de)接(jie)(jie)地(di)(di)統(tong)還是原建(jian)筑的(de)(de)(de)(de)(de)(de)接(jie)(jie)地(di)(di)線(xian)(xian)(xian)(xian)，接(jie)(jie)地(di)(di)電(dian)阻(zu)都(dou)應(ying)(ying)(ying)(ying)(ying)小(xiao)(xiao)于4歐(ou)姆，除天(tian)(tian)(tian)線(xian)(xian)(xian)(xian)應(ying)(ying)(ying)(ying)(ying)有(you)(you)良好的(de)(de)(de)(de)(de)(de)避(bi)(bi)雷(lei)(lei)的(de)(de)(de)(de)(de)(de)接(jie)(jie)地(di)(di)外(wai)，還應(ying)(ying)(ying)(ying)(ying)采取如下(xia)措施：①無(wu)線(xian)(xian)(xian)(xian)輸出端(duan)應(ying)(ying)(ying)(ying)(ying)安裝(zhuang)專(zhuan)用(yong)(yong)CATV保(bao)(bao)安器；②天(tian)(tian)(tian)線(xian)(xian)(xian)(xian)輸出電(dian)纜按接(jie)(jie)地(di)(di)要求接(jie)(jie)地(di)(di)；③使用(yong)(yong)裝(zhuang)有(you)(you)氣(qi)體放(fang)電(dian)管及快速反應(ying)(ying)(ying)(ying)(ying)保(bao)(bao)護(hu)二級(ji)管的(de)(de)(de)(de)(de)(de)天(tian)(tian)(tian)線(xian)(xian)(xian)(xian)放(fang)大器或頻道放(fang)大器。

2.前端設(she)備的(de)防(fang)雷接(jie)地(di)(di)(di)(di)。如(ru)果(guo)在前端附近發(fa)生雷擊，則會在機(ji)房內(nei)的(de)金(jin)屬機(ji)箱和(he)外殼上感(gan)應出(chu)高電(dian)(dian)(dian)壓，危及(ji)設(she)備及(ji)人身安(an)全(quan)。前端設(she)備的(de)電(dian)(dian)(dian)源漏電(dian)(dian)(dian)也(ye)會危及(ji)人員(yuan)的(de)安(an)全(quan)，因此，對機(ji)房內(nei)的(de)所有(you)設(she)備，輸入、輸出(chu)電(dian)(dian)(dian)纜的(de)屏(ping)蔽(bi)層(ceng)，金(jin)屬管道等都需(xu)要接(jie)地(di)(di)(di)(di)，不(bu)能與層(ceng)頂天線(xian)(xian)的(de)接(jie)地(di)(di)(di)(di)接(jie)在一起(qi)，設(she)備接(jie)地(di)(di)(di)(di)與房屋避雷針(zhen)(zhen)接(jie)地(di)(di)(di)(di)及(ji)工(gong)頻交流供電(dian)(dian)(dian)系(xi)(xi)統的(de)接(jie)地(di)(di)(di)(di)應在總接(jie)地(di)(di)(di)(di)處連(lian)接(jie)在一起(qi)。系(xi)(xi)統內(nei)的(de)電(dian)(dian)(dian)氣設(she)備接(jie)地(di)(di)(di)(di)裝(zhuang)置和(he)埋地(di)(di)(di)(di)金(jin)屬管道應與防(fang)雷接(jie)地(di)(di)(di)(di)裝(zhuang)置相連(lian)，不(bu)相連(lian)時兩者的(de)距離應大于3米，機(ji)房內(nei)接(jie)地(di)(di)(di)(di)母線(xian)(xian)表面應完整，并無(wu)明顯(xian)錘痕(hen)以(yi)及(ji)殘余焊劑(ji)渣(zha)；銅(tong)帶母線(xian)(xian)應光滑無(wu)毛刺。絕緣線(xian)(xian)的(de)老化層(ceng)不(bu)應有(you)老化龜裂現(xian)象。一些前端設(she)備如(ru)調制器，接(jie)收機(ji)等沒有(you)過壓保(bao)護(hu)，而(er)只有(you)過流保(bao)護(hu)，一旦有(you)雷擊物往會出(chu)現(xian)電(dian)(dian)(dian)源燒(shao)壞而(er)保(bao)險(xian)不(bu)斷的(de)情(qing)況，針(zhen)(zhen)對此種(zhong)情(qing)況應在總電(dian)(dian)(dian)源處加裝(zhuang)避雷器，以(yi)更(geng)好的(de)保(bao)護(hu)前端設(she)備。

3.干(gan)線和分配系統的防(fang)雷接地。

①敷設于空(kong)曠地(di)(di)區的地(di)(di)下電纜(lan)，當所在地(di)(di)區年雷暴天數大于20天及(ji)土(tu)壤電阻(zu)率大于100歐姆時(shi)，電纜(lan)的屏蔽層或金(jin)屬護套(tao)應每隔2KM左(zuo)右接地(di)(di)一次(ci)。

 ②架(jia)空(kong)電(dian)纜(lan)的(de)屏蔽層及金屬護套(tao)(tao)、鋼紋吊線每隔250M左(zuo)右接(jie)地(di)(di)一次，在電(dian)纜(lan)分(fen)線箱(xiang)處(chu)的(de)架(jia)空(kong)電(dian)纜(lan)金屬護套(tao)(tao)，屏蔽層及鋼絞線應與電(dian)纜(lan)分(fen)線精會(hui)用接(jie)地(di)(di)裝置。埋(mai)設于空(kong)曠地(di)(di)區地(di)(di)下電(dian)纜(lan)，其屏蔽層和護套(tao)(tao)，應每隔2KM左(zuo)右接(jie)地(di)(di)一次，以(yi)防(fang)止感應電(dian)的(de)影響。

 ③電纜進入建筑物時，在靠(kao)近建筑物的地方(fang)，應(ying)將電纜的外導電屏蔽層接(jie)地，架(jia)空電纜直接(jie)引(yin)入時，在入戶處應(ying)增設避雷器(qi)，并(bing)將電纜外導體(ti)接(jie)到電氣設備(bei)的接(jie)地裝置上，電纜直接(jie)埋地引(yin)入時，應(ying)在入戶端將電纜金屬(shu)外皮與接(jie)地裝置相連。

 ④不要(yao)直接在(zai)兩建(jian)筑(zhu)物屋頂之間敷設(she)(she)電(dian)(dian)(dian)纜(lan)，可將電(dian)(dian)(dian)纜(lan)沿(yan)墻(qiang)降至防雷(lei)保(bao)護區(qu)以(yi)內，并(bing)不得防礙車輛的運行，吊線(xian)應作(zuo)接地處理(li)。⑤系統中設(she)(she)備(bei)的輸(shu)入輸(shu)出(chu)端應有氣(qi)體放(fang)(fang)電(dian)(dian)(dian)保(bao)護管，220V供電(dian)(dian)(dian)的放(fang)(fang)大(da)器(qi)的電(dian)(dian)(dian)源(yuan)端應有過(guo)(guo)(guo)壓(ya)保(bao)護裝置，目前市面(mian)上的放(fang)(fang)大(da)器(qi)魚(yu)龍混雜，為了降低成本，甚至省去了防過(guo)(guo)(guo)壓(ya)措施，如(ru)輸(shu)入輸(shu)出(chu)瑞元氣(qi)體過(guo)(guo)(guo)壓(ya)放(fang)(fang)電(dian)(dian)(dian)管，220V供電(dian)(dian)(dian)的放(fang)(fang)大(da)器(qi)電(dian)(dian)(dian)源(yuan)端只有過(guo)(guo)(guo)流保(bao)護，而無(wu)過(guo)(guo)(guo)壓(ya)保(bao)護，在(zai)選用干線(xian)器(qi)材時，應把防過(guo)(guo)(guo)壓(ya)保(bao)護作(zuo)為一(yi)個重(zhong)要(yao)的前提條(tiao)件(jian)來考慮。

 ⑤CATV系統(tong)中的(de)同軸(zhou)電纜屏蔽網和架(jia)空支撐電纜用的(de)鍍鋅鐵線(xian)都有良好(hao)的(de)接(jie)地。

 4.CATV系統中的同軸電(dian)(dian)纜(lan)屏(ping)蔽網和架空支承(cheng)電(dian)(dian)纜(lan)用的鍍鋅鐵線(xian)都有(you)良好(hao)的接(jie)地(di)(di)，受感應雷(lei)的機會較小，雷(lei)電(dian)(dian)最(zui)容易從電(dian)(dian)源線(xian)進入(ru)(ru)電(dian)(dian)子(zi)設(she)備(bei)，把(ba)供(gong)電(dian)(dian)線(xian)進戶(hu)瓷瓶鐵腳接(jie)地(di)(di)，對(dui)保護電(dian)(dian)力(li)設(she)備(bei)和人身安(an)全可(ke)以(yi)起到一定的作(zuo)用，由于CATV等(deng)電(dian)(dian)子(zi)設(she)備(bei)的耐(nai)受過電(dian)(dian)壓(ya)的能力(li)比電(dian)(dian)力(li)設(she)備(bei)差(cha)得多，因此除必(bi)須在(zai)進戶(hu)線(xian)上安(an)裝(zhuang)低(di)壓(ya)避雷(lei)器外，可(ke)把(ba)光屏(ping)蔽的電(dian)(dian)線(xian)、電(dian)(dian)纜(lan)等(deng)在(zai)埋地(di)(di)金(jin)屬管中，使(shi)雷(lei)電(dian)(dian)波通入(ru)(ru)地(di)(di)中。電(dian)(dian)源線(xian)在(zai)進入(ru)(ru)電(dian)(dian)子(zi)設(she)備(bei)前(qian)可(ke)繞幾個圈以(yi)形成小電(dian)(dian)感，對(dui)50HZ電(dian)(dian)流沒(mei)有(you)什么影響，對(dui)阻擋雷(lei)電(dian)(dian)波侵入(ru)(ru)設(she)備(bei)卻(que)有(you)一定作(zuo)用。

在系(xi)統(tong)(tong)(tong)接(jie)地時(shi)，一(yi)定注意接(jie)地電阻的(de)最小(xiao)化，接(jie)地電阻大防(fang)雷(lei)(lei)效果就差，盡量(liang)的(de)減(jian)小(xiao)接(jie)地電阻、控制(zhi)在8歐(ou)姆以下為(wei)最好。有線電視系(xi)統(tong)(tong)(tong)的(de)防(fang)雷(lei)(lei)是一(yi)項綜合的(de)技(ji)術工程，任(ren)何一(yi)個(ge)環節出了漏洞(dong)，都會(hui)影響整個(ge)系(xi)統(tong)(tong)(tong)的(de)防(fang)雷(lei)(lei)效果。在做(zuo)系(xi)統(tong)(tong)(tong)的(de)防(fang)雷(lei)(lei)設(she)計時(shi)一(yi)定要本著科(ke)學嚴謹(jin)的(de)態度，切實(shi)做(zuo)好系(xi)統(tong)(tong)(tong)的(de)防(fang)護(hu)設(she)計。

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