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触电安全防护

2018-01-17  

1、安全电(dian)压(ya)

安(an)全(quan)(quan)(quan)(quan)(quan)电(dian)(dian)(dian)压(ya)是(shi)制订电(dian)(dian)(dian)气安(an)全(quan)(quan)(quan)(quan)(quan)规(gui)(gui)程和(he)(he)(he)一系(xi)列(lie)电(dian)(dian)(dian)气安(an)全(quan)(quan)(quan)(quan)(quan)技(ji)术措施(shi)的(de)基础数据(ju),它(ta)取决于人(ren)体(ti)电(dian)(dian)(dian)阻和(he)(he)(he)人(ren)体(ti)允许通(tong)过的(de)电(dian)(dian)(dian)流。世界各国对(dui)安(an)全(quan)(quan)(quan)(quan)(quan)电(dian)(dian)(dian)压(ya)值(zhi)的(de)规(gui)(gui)定也(ye)(ye)各异,采用(yong)(yong)50 V和(he)(he)(he)25 V的(de)居多,也(ye)(ye)有规(gui)(gui)定40 V、36 V或24 V的(de)。国际电(dian)(dian)(dian)工委(wei)员会(hui)(IEC)规(gui)(gui)定的(de)接(jie)触(chu)电(dian)(dian)(dian)压(ya)限值(zhi)(相当于安(an)全(quan)(quan)(quan)(quan)(quan)电(dian)(dian)(dian)压(ya))为(wei)(wei)50 V、并规(gui)(gui)定25 V以(yi)(yi)下(xia)不需考虑防止电(dian)(dian)(dian)击的(de)安(an)全(quan)(quan)(quan)(quan)(quan)措施(shi)。国外还有在特殊情(qing)况下(xia)采用(yong)(yong)25 V安(an)全(quan)(quan)(quan)(quan)(quan)电(dian)(dian)(dian)压(ya)值(zhi)的(de)。我国的(de)安(an)全(quan)(quan)(quan)(quan)(quan)电(dian)(dian)(dian)压(ya)为(wei)(wei)36 V和(he)(he)(he)12 V。如无特殊安(an)全(quan)(quan)(quan)(quan)(quan)结构和(he)(he)(he)安(an)全(quan)(quan)(quan)(quan)(quan)措施(shi),危险(xian)环境和(he)(he)(he)特别危险(xian)环境的(de)局部照明、手提照明灯等(deng),其安(an)全(quan)(quan)(quan)(quan)(quan)电(dian)(dian)(dian)压(ya)应为(wei)(wei)36 V;工作地点狭窄,周(zhou)围(wei)有大面(mian)积接(jie)地导体(ti)环境(如金(jin)属容(rong)器内(nei)) 的(de)手提照明灯,其安(an)全(quan)(quan)(quan)(quan)(quan)电(dian)(dian)(dian)压(ya)应采用(yong)(yong)12 V。触(chu)电(dian)(dian)(dian)事故中(zhong),绝(jue)大部分是(shi)受电(dian)(dian)(dian)流遭到电(dian)(dian)(dian)击导致(zhi)人(ren)身(shen)伤亡的(de)。人(ren)的(de)平(ping)均电(dian)(dian)(dian)阻为(wei)(wei)1000一1500欧姆,电(dian)(dian)(dian)流为(wei)(wei)50毫安(an)时,称(cheng)为(wei)(wei)致(zhi)命电(dian)(dian)(dian)流.安(an)全(quan)(quan)(quan)(quan)(quan)电(dian)(dian)(dian)压(ya)是(shi)指保证不会(hui)对(dui)人(ren)体(ti)产生致(zhi)命危险(xian)的(de)电(dian)(dian)(dian)压(ya)值(zhi),工业(ye)中(zhong)使用(yong)(yong)的(de)安(an)全(quan)(quan)(quan)(quan)(quan)电(dian)(dian)(dian)压(ya)是(shi)36V以(yi)(yi)下(xia)。

在有(you)电(dian)(dian)(dian)阻、电(dian)(dian)(dian)容、电(dian)(dian)(dian)感的电(dian)(dian)(dian)路(lu)中,电(dian)(dian)(dian)源电(dian)(dian)(dian)压(ya)(ya)是(shi)几十(shi)伏(fu),电(dian)(dian)(dian)容或电(dian)(dian)(dian)感的电(dian)(dian)(dian)压(ya)(ya)可以超过百伏(fu)特。电(dian)(dian)(dian)源电(dian)(dian)(dian)压(ya)(ya)高于电(dian)(dian)(dian)容耐(nai)压(ya)(ya)时(shi),会引起(qi)电(dian)(dian)(dian)容爆裂(lie)而伤害到人(ren)。在强电(dian)(dian)(dian)实(shi)(shi)验(yan)时(shi),实(shi)(shi)验(yan)人(ren)员必须(xu)2人(ren)以上(shang)。万用(yong)表使用(yong)完后,应将切换旋钮放在交流电(dian)(dian)(dian)压(ya)(ya)最高档。对于高压(ya)(ya)电(dian)(dian)(dian)容器,实(shi)(shi)验(yan)结束后或闲置时(shi)应该双电(dian)(dian)(dian)极(ji)短(duan)接串接合适电(dian)(dian)(dian)阻进行放电(dian)(dian)(dian)。

2、绝缘(yuan)

通常(chang)采用的(de)绝(jue)缘(yuan)材(cai)料(liao)有陶(tao)瓷、橡胶、塑料(liao)、云(yun)母、玻璃、木材(cai)、布、纸、矿物(wu)油,以(yi)及(ji)某些高分子合成材(cai)料(liao)等(deng)。绝(jue)缘(yuan)材(cai)料(liao)的(de)性能受环境条件(jian)影响较大,温度、湿度都会(hui)改变(bian)其(qi)电阻车,机(ji)械损(sun)伤和化学(xue)腐(fu)蚀等(deng)也会(hui)降低绝(jue)缘(yuan)材(cai)料(liao)的(de)绝(jue)缘(yuan)电阻值,对于(yu)一些高分子材(cai)料(liao),还存在由于(yu)“老化”导致的(de)绝(jue)缘(yuan)性能逐步(bu)下降的(de)问题。

长期搁置不用(yong)(yong)的(de)手持电(dian)(dian)动工具,在使用(yong)(yong)前(qian)必(bi)须(xu)测(ce)量(liang)绝(jue)缘(yuan)电(dian)(dian)阻,要求手持电(dian)(dian)动工具带电(dian)(dian)部分(fen)与(yu)外(wai)壳之间绝(jue)缘(yuan)电(dian)(dian)阻不低于0.5MΩ。移(yi)动式(shi)电(dian)(dian)动工具及其开关板(箱)的(de)电(dian)(dian)源线必(bi)须(xu)采(cai)用(yong)(yong)铜芯(xin)(xin)橡(xiang)皮绝(jue)缘(yuan)护套(tao)或铜芯(xin)(xin)聚氯乙烯绝(jue)缘(yuan)护套(tao)软线。

3、屏护

某些开(kai)启式开(kai)关电(dian)(dian)器的(de)(de)活动(dong)部分(fen)不便绝(jue)(jue)缘(yuan),或(huo)高压设备的(de)(de)绝(jue)(jue)缘(yuan)不能保证(zheng)人在(zai)接近时的(de)(de)安(an)全,应采(cai)取屏(ping)护措施(shi),以(yi)(yi)免触(chu)电(dian)(dian)或(huo)电(dian)(dian)弧伤(shang)人等事故。屏(ping)护装(zhuang)置(zhi)的(de)(de)形式有(you)(you)(you)围墙、栅栏、护网、护罩等。所用(yong)材料应有(you)(you)(you)足够(gou)的(de)(de)机械强(qiang)度和耐火性能,若(ruo)采(cai)用(yong)金(jin)属材料,则必须接地或(huo)接零。屏(ping)护装(zhuang)置(zhi)应有(you)(you)(you)足够(gou)的(de)(de)尺(chi)寸,并与(yu)带电(dian)(dian)体保持足够(gou)的(de)(de)距离,在(zai)带电(dian)(dian)体及屏(ping)护装(zhuang)置(zhi)上应有(you)(you)(you)明显的(de)(de)警告标志,必要(yao)时还可附加声(sheng)光(guang)报警和联锁装(zhuang)置(zhi)等,以(yi)(yi)最大限度保证(zheng)屏(ping)护的(de)(de)有(you)(you)(you)效(xiao)性。

4、间(jian)距(ju)

在带(dai)电(dian)(dian)体与地面之间(jian)、带(dai)电(dian)(dian)体与其他设备之间(jian)、带(dai)电(dian)(dian)体之间(jian),均需(xu)保(bao)持(chi)一定的(de)安(an)全距(ju)离(li),以(yi)防(fang)止过电(dian)(dian)压放电(dian)(dian)和各(ge)种(zhong)短路事(shi)故,以(yi)及由这些事(shi)故导致(zhi)的(de)火灾。

动力或照(zhao)明配电箱(柜、板)周围(wei)不得堆放杂物;其前方(fang)1.2米范围(wei)内应无障碍物保持畅通

电线接地时,人体(ti)距离(li)接地点越近,跨步电压越高(gao);距离(li)越远,跨步电压越低。一般情况下距离(li)接地体(ti)20m以外跨步电压可看成是(shi)零。高(gao)压实验中的(de)安全(quan)距离(li): 10kV是(shi)0.7m;66kV是(shi)1.5m;220kV是(shi)3m。

5、接(jie)(jie)地与接(jie)(jie)零

接(jie)地(di)是指把电(dian)(dian)气设(she)备的(de)某一部分通过接(jie)地(di)装置(zhi)同大(da)地(di)连接(jie)起来(lai);接(jie)零是指把电(dian)(dian)气设(she)备正常时不带电(dian)(dian)的(de)导(dao)电(dian)(dian)部分(如(ru)金属机壳) 同电(dian)(dian)网的(de)零线连接(jie)起来(lai)。接(jie)地(di)与接(jie)零是防止电(dian)(dian)气设(she)备一旦漏电(dian)(dian)而可(ke)能发生触(chu)电(dian)(dian)事故(gu)的(de)重(zhong)要安(an)全措施。

   (1) 保护接地

   保护接地(di)是广泛应用的(de)(de)(de)安全技术措(cuo)施,主要适用于三(san)相三(san)线制中性点不(bu)直接接地(di)的(de)(de)(de)电(dian)力系统中。在对地(di)绝缘(yuan)的(de)(de)(de)电(dian)网中,除非另有规定,否则(ze)凡由于绝缘(yuan)破坏或其他原因而(er)可能(neng)呈现危险电(dian)压的(de)(de)(de)金属(shu)部分,均(jun)应接地(di)。

   (2) 保护接零(ling)

   保护(hu)接(jie)零(ling)(ling)是将电气设备正常(chang)运行时不带电的(de)导电部分(fen)与(yu)(yu)电网地零(ling)(ling)线(xian)(xian)(即中性线(xian)(xian)) 连(lian)接(jie)起来,用(yong)(yong)以防止触(chu)电事故的(de)发生。保护(hu)接(jie)零(ling)(ling)通常(chang)用(yong)(yong)于(yu)中性点(dian)直接(jie)接(jie)地、380/220 V的(de)三(san)相四(si)线(xian)(xian)制电网中,还要与(yu)(yu)其他安全措施(如熔断(duan)(duan)器、断(duan)(duan)路器等) 配合使用(yong)(yong),才能达到目的(de)。

 (3) 高压窜入(ru)低压时的保(bao)护

   当变压(ya)器高(gao)(gao)压(ya)侧与(yu)低(di)压(ya)侧之(zhi)间的(de)绝缘损坏(huai)、或高(gao)(gao)压(ya)线路断线搭落在低(di)压(ya)配电线路上(shang)时,都可能发生高(gao)(gao)压(ya)窜(cuan)入低(di)压(ya)。为防止和减少这种危险(xian),在中(zhong)(zhong)(zhong)(zhong)性点(dian)不接地的(de)低(di)压(ya)配电系统中(zhong)(zhong)(zhong)(zhong),除了(le)采取可靠的(de)保护接地之(zhi)外,还(hai)应有(you)防止高(gao)(gao)压(ya)窜(cuan)入低(di)压(ya)的(de)保护措施。为此,在中(zhong)(zhong)(zhong)(zhong)性点(dian)不接地的(de)低(di)压(ya)电网中(zhong)(zhong)(zhong)(zhong),应使(shi)其(qi)中(zhong)(zhong)(zhong)(zhong)性点(dian)或某(mou)一相经过击穿(chuan)保险(xian)器与(yu)大地连接。

在正常情况下(xia),低压系统保(bao)持不接地。当(dang)高压窜入低压时,去穿(chuan)保(bao)险器被击(ji)穿(chuan),故(gu)障(zhang)电(dian)(dian)流经接地装置流入大(da)地,同时使高压系统相应(ying)的保(bao)护装置动作,切断电(dian)(dian)源,起到(dao)保(bao)护作用。   在雷击(ji)时,如果作业人员孤立处(chu)于暴露区(qu)并感到(dao)头(tou)发竖起时,应(ying)该立即双(shuang)膝下(xia)蹲,向前(qian)弯(wan)曲(qu),双(shuang)手抱膝。

   (4) 重(zhong)复接地(di)

   为保(bao)(bao)证保(bao)(bao)护接零(ling)(ling)系统(tong)的安(an)全,将零(ling)(ling)线上的一处或多(duo)处通过接地(di)装置与大地(di)重复连接,称为重复接地(di),其作用是:

   1) 降低漏电(dian)(dian)(dian)(dian)设(she)备(bei)的对地电(dian)(dian)(dian)(dian)压,漏电(dian)(dian)(dian)(dian)保护(hu)(hu)器(qi)(qi)(qi)既可(ke)用来(lai)保护(hu)(hu)人身安全,还(hai)可(ke)用来(lai)对低压系统或设(she)备(bei)的绝(jue)缘状况起到(dao)监督作(zuo)用;漏电(dian)(dian)(dian)(dian)保护(hu)(hu)器(qi)(qi)(qi)安装点(dian)以后的线(xian)路应是对地绝(jue)缘良好 ;漏电(dian)(dian)(dian)(dian)保护(hu)(hu)器(qi)(qi)(qi)对两相触(chu)电(dian)(dian)(dian)(dian)(人体双手触(chu)及(ji)两相电(dian)(dian)(dian)(dian)源),不起保护(hu)(hu)作(zuo)用。

   2) 减(jian)少(shao)零线(xian)断线(xian)时的危(wei)险。另(ling)外,也使三相负荷不平衡导致零线(xian)对地电压(ya)有所下降,从而减(jian)少(shao)了危(wei)险。

   3) 缩短(duan)(duan)了短(duan)(duan)路(lu)故(gu)障的持续时间(jian)。由于重复(fu)援地与工作接地形成并联,使短(duan)(duan)路(lu)电流(liu)加大,从而加快了断路(lu)器的动作时间(jian)。

   4) 改善了(le)架空线路的(de)防(fang)雷性能。可(ke)以对雷电(dian)流进行(xing)分流,从而限制(zhi)了(le)雷电(dian)产生(sheng)的(de)过电(dian)压。

   5)重复(fu)接(jie)地(di)是指(zhi)零线(xian)上的一处或多(duo)处通(tong)过接(jie)地(di)装置(zhi)与大地(di)再连(lian)接(jie),可提高线(xian)路的安(an)全(quan)性

6、漏电保护装置

漏(lou)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)保护装置是在电(dian)(dian)(dian)(dian)(dian)(dian)(dian)气(qi)设(she)备成线(xian)路(lu)漏(lou)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)时用(yong)以保证人身(shen)及设(she)备安全(quan)的保护装置,又称触电(dian)(dian)(dian)(dian)(dian)(dian)(dian)保安器。设(she)备漏(lou)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)时会出(chu)(chu)现两(liang)种异(yi)常现象: 正常情况下不带(dai)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)的金属部分出(chu)(chu)现对地电(dian)(dian)(dian)(dian)(dian)(dian)(dian)压;三相(xiang)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)平(ping)衡被破坏,出(chu)(chu)现零序电(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(或(huo)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)压) 。漏(lou)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)保护装置,就是在故障时测得(de)零序电(dian)(dian)(dian)(dian)(dian)(dian)(dian)流(liu)(liu)(或(huo)电(dian)(dian)(dian)(dian)(dian)(dian)(dian)压) 或(huo)对地电(dian)(dian)(dian)(dian)(dian)(dian)(dian)压,经(jing)相(xiang)应转换,使接触器跳闸,切断电(dian)(dian)(dian)(dian)(dian)(dian)(dian)源,实施保护作用(yong)。



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