电磁兼容小小家EMCHOME雷击浪涌资料-下载防雷设计与电源技术低压电网防雷电过电压保护（文摘）黄健华　(广东工业大学建筑设计研究院,广东　广州市　510090)摘　要:介绍了低压避雷器在低压电网防雷电过电压中的实际应用。关键词:低压电网;雷电过电压;低压避雷器1 　 ...

pwm 发表于 2006-12-31 11:07:45

低压电网防雷电过电压保护（文摘）

黄健华　(广东工业大学建筑设计研究院,广东　广州市　510090) 摘　要:介绍了低压避雷器在低压电网防雷电过电压中的实际应用。 关键词:低压电网;雷电过电压;低压避雷器 1 　雷电过电压的特性与避雷器 雷电是一种自然现象,具有很大的破坏性。所谓雷电是指一部分带电的云层对另一部分带异种电荷的云层或者是带电的云层对大地之间迅猛的放电。其中,云层对大地的放电对人、动物、建筑物、电气设备、通讯网络等造成的破坏很大,甚至造成巨大的经济损失。为了确保人身设备的安全和连续供电,正确有效地抑制低压电网上出现的过电压,主要采用低压避雷器保护设备。这就需要根据雷电的特点来考虑保护设备承受雷电过电压的特性。 雷电主要分为直击雷和非直击雷(包括感应雷和传导雷) 。据资料显示,对直接雷击架空线和电站进行统计,约有50 %雷电电流峰值超过25kA ,只有不到1 %雷电电流峰值超过180kA(见表1) 。雷电冲击脉冲的上升沿可达100kAPμs ,持续时间可达数十毫秒,根据统计数据可描绘出雷电电流波形(如图1所示) 。而架空线上的传导雷过电压可达几十万伏,据统计,高压侧4 %的过电压可耦合到低压侧,其中过电压值为4kV 以下的占91 % ,98 %的过电压值不超过6kV ,这类间接雷电还可产生高速变化的电磁场,在雷电区闪电辐射的电场可达50kVPm ,产生很高的开路电压作用在大气中。这类电压具有很陡的上升沿并且衰减很快,对其雷电过电压和过电流统计后得到标准波形(如图2 所示) 。根据这两个波形考虑避雷器承受雷电过电压的特性。 表1 　雷电主要特性 出现几率电流峰值负荷上升率∫I2 dt 持续时间放电次数<table style="WIDTH: 378pt; BORDER-COLLAPSE: collapse" cellspacing="0" cellpadding="0" width="504" border="0"><colgroup><col style="WIDTH: 54pt" span="7" width="72" /></colgroup><tbody><tr style="HEIGHT: 15pt" height="20"><td class="xl24" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt solid; BORDER-LEFT: windowtext 0.5pt solid; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; HEIGHT: 15pt; BACKGROUND-COLOR: transparent" width="72" height="20">出现几率</td><td class="xl25" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt solid; BORDER-LEFT: windowtext 0.5pt dotted; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width="72">电流峰值</td><td class="xl25" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt solid; BORDER-LEFT: windowtext 0.5pt dotted; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width="72">负荷</td><td class="xl25" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt solid; BORDER-LEFT: windowtext 0.5pt dotted; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width="72">上升率</td><td class="xl25" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt solid; BORDER-LEFT: windowtext 0.5pt dotted; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width="72">∫I6 dt </td><td class="xl25" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt solid; BORDER-LEFT: windowtext 0.5pt dotted; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width="72">持续时间</td><td class="xl25" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt solid; BORDER-LEFT: windowtext 0.5pt dotted; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width="72">放电次数</td></tr><tr style="HEIGHT: 30pt" height="40"><td class="xl26" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt dotted; BORDER-LEFT: windowtext 0.5pt solid; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; HEIGHT: 30pt; BACKGROUND-COLOR: transparent" width="72" height="40">P( %)</td><td class="xl27" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt dotted; BORDER-LEFT: windowtext 0.5pt dotted; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width="72">I(kA)</td><td class="xl27" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt dotted; BORDER-LEFT: windowtext 0.5pt dotted; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width="72">Q©</td><td class="xl27" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt dotted; BORDER-LEFT: windowtext 0.5pt dotted; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width="72">S(kAPμs)</td><td class="xl27" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt dotted; BORDER-LEFT: windowtext 0.5pt dotted; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width="72">(kA6 . s)</td><td class="xl27" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt dotted; BORDER-LEFT: windowtext 0.5pt dotted; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width="72">T(s)</td><td class="xl27" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt dotted; BORDER-LEFT: windowtext 0.5pt dotted; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width="72">N</td></tr><tr style="HEIGHT: 15pt" height="20"><td class="xl26" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt dotted; BORDER-LEFT: windowtext 0.5pt solid; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; HEIGHT: 15pt; BACKGROUND-COLOR: transparent" width="72" height="20">50</td><td class="xl27" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt dotted; BORDER-LEFT: windowtext 0.5pt dotted; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width="72">26</td><td class="xl27" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt dotted; BORDER-LEFT: windowtext 0.5pt dotted; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width="72">14</td><td class="xl27" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt dotted; BORDER-LEFT: windowtext 0.5pt dotted; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width="72">18</td><td class="xl27" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt dotted; BORDER-LEFT: windowtext 0.5pt dotted; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width="72">0.54</td><td class="xl27" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt dotted; BORDER-LEFT: windowtext 0.5pt dotted; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width="72">0.09</td><td class="xl27" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt dotted; BORDER-LEFT: windowtext 0.5pt dotted; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width="72">1.8</td></tr><tr style="HEIGHT: 15pt" height="20"><td class="xl26" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt dotted; BORDER-LEFT: windowtext 0.5pt solid; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; HEIGHT: 15pt; BACKGROUND-COLOR: transparent" width="72" height="20">10</td><td class="xl27" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt dotted; BORDER-LEFT: windowtext 0.5pt dotted; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width="72">73</td><td class="xl27" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt dotted; BORDER-LEFT: windowtext 0.5pt dotted; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width="72">70</td><td class="xl27" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt dotted; BORDER-LEFT: windowtext 0.5pt dotted; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width="72">7</td><td class="xl27" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt dotted; BORDER-LEFT: windowtext 0.5pt dotted; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width="72">1.9</td><td class="xl27" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt dotted; BORDER-LEFT: windowtext 0.5pt dotted; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width="72">0.56</td><td class="xl27" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt dotted; BORDER-LEFT: windowtext 0.5pt dotted; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width="72">5</td></tr><tr style="HEIGHT: 15pt" height="20"><td class="xl26" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt dotted; BORDER-LEFT: windowtext 0.5pt solid; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; HEIGHT: 15pt; BACKGROUND-COLOR: transparent" width="72" height="20">1</td><td class="xl27" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt dotted; BORDER-LEFT: windowtext 0.5pt dotted; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width="72">180</td><td class="xl27" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt dotted; BORDER-LEFT: windowtext 0.5pt dotted; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width="72">330</td><td class="xl27" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt dotted; BORDER-LEFT: windowtext 0.5pt dotted; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width="72">97</td><td class="xl27" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt dotted; BORDER-LEFT: windowtext 0.5pt dotted; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width="72">35</td><td class="xl27" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt dotted; BORDER-LEFT: windowtext 0.5pt dotted; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width="72">2.7</td><td class="xl27" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt dotted; BORDER-LEFT: windowtext 0.5pt dotted; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width="72">12</td></tr></tbody></table> 低压避雷器必须承受预期通过它们的雷电流,对过电压峰值进行限幅,熄灭在雷电流通过后产生的工频续流。低压避雷器的耐受冲击过电压等级取决于它本身的两个主要电气性能参数,即空气间隙和爬电距离。空气间隙指的是两导体之间的最短距离。爬电距离指的是两个导电部分之间的绝缘材料沿表面的最短距离。避雷器在施工布置时应有足够的空气间隙和爬电距离。安装在低压配电系统不同界面上的低压避雷器应与保护系统的基本绝缘水平、冲击耐受电压一致。一般8/20us电流波形、1.2/50us电压波形/选择。 <img src="http://www.binghong3d.com/./upload_news_img/11674461063000.jpg" align="baseline" border="0" />图1 　雷电电流波形表2 　220P380V 三相系统各种设备<table style="WIDTH: 378pt; BORDER-COLLAPSE: collapse" cellspacing="0" cellpadding="0" width="504" border="0"><colgroup><col style="WIDTH: 54pt" span="7" width="72" /></colgroup><tbody><tr style="HEIGHT: 15pt" height="20"><td class="xl24" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt solid; BORDER-LEFT: windowtext 0.5pt solid; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; HEIGHT: 15pt; BACKGROUND-COLOR: transparent" width="72" height="20">出现几率</td><td class="xl25" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt solid; BORDER-LEFT: windowtext 0.5pt dotted; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width="72">电流峰值</td><td class="xl25" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt solid; BORDER-LEFT: windowtext 0.5pt dotted; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width="72">负荷</td><td class="xl25" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt solid; BORDER-LEFT: windowtext 0.5pt dotted; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width="72">上升率</td><td class="xl25" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt solid; BORDER-LEFT: windowtext 0.5pt dotted; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width="72">∫I6 dt </td><td class="xl25" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt solid; BORDER-LEFT: windowtext 0.5pt dotted; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width="72">持续时间</td><td class="xl25" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt solid; BORDER-LEFT: windowtext 0.5pt dotted; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width="72">放电次数</td></tr><tr style="HEIGHT: 30pt" height="40"><td class="xl26" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt dotted; BORDER-LEFT: windowtext 0.5pt solid; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; HEIGHT: 30pt; BACKGROUND-COLOR: transparent" width="72" height="40">P( %)</td><td class="xl27" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt dotted; BORDER-LEFT: windowtext 0.5pt dotted; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width="72">I(kA)</td><td class="xl27" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt dotted; BORDER-LEFT: windowtext 0.5pt dotted; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width="72">Q©</td><td class="xl27" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt dotted; BORDER-LEFT: windowtext 0.5pt dotted; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width="72">S(kAPμs)</td><td class="xl27" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt dotted; BORDER-LEFT: windowtext 0.5pt dotted; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width="72">(kA6 . s)</td><td class="xl27" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt dotted; BORDER-LEFT: windowtext 0.5pt dotted; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width="72">T(s)</td><td class="xl27" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt dotted; BORDER-LEFT: windowtext 0.5pt dotted; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width="72">N</td></tr><tr style="HEIGHT: 15pt" height="20"><td class="xl26" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt dotted; BORDER-LEFT: windowtext 0.5pt solid; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; HEIGHT: 15pt; BACKGROUND-COLOR: transparent" width="72" height="20">50</td><td class="xl27" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt dotted; BORDER-LEFT: windowtext 0.5pt dotted; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width="72">26</td><td class="xl27" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt dotted; BORDER-LEFT: windowtext 0.5pt dotted; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width="72">14</td><td class="xl27" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt dotted; BORDER-LEFT: windowtext 0.5pt dotted; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width="72">18</td><td class="xl27" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt dotted; BORDER-LEFT: windowtext 0.5pt dotted; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width="72">0.54</td><td class="xl27" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt dotted; BORDER-LEFT: windowtext 0.5pt dotted; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width="72">0.09</td><td class="xl27" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt dotted; BORDER-LEFT: windowtext 0.5pt dotted; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width="72">1.8</td></tr><tr style="HEIGHT: 15pt" height="20"><td class="xl26" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt dotted; BORDER-LEFT: windowtext 0.5pt solid; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; HEIGHT: 15pt; BACKGROUND-COLOR: transparent" width="72" height="20">10</td><td class="xl27" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt dotted; BORDER-LEFT: windowtext 0.5pt dotted; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width="72">73</td><td class="xl27" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt dotted; BORDER-LEFT: windowtext 0.5pt dotted; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width="72">70</td><td class="xl27" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt dotted; BORDER-LEFT: windowtext 0.5pt dotted; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width="72">7</td><td class="xl27" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt dotted; BORDER-LEFT: windowtext 0.5pt dotted; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width="72">1.9</td><td class="xl27" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt dotted; BORDER-LEFT: windowtext 0.5pt dotted; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width="72">0.56</td><td class="xl27" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt dotted; BORDER-LEFT: windowtext 0.5pt dotted; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width="72">5</td></tr><tr style="HEIGHT: 15pt" height="20"><td class="xl26" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt dotted; BORDER-LEFT: windowtext 0.5pt solid; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; HEIGHT: 15pt; BACKGROUND-COLOR: transparent" width="72" height="20">1</td><td class="xl27" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt dotted; BORDER-LEFT: windowtext 0.5pt dotted; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width="72">180</td><td class="xl27" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt dotted; BORDER-LEFT: windowtext 0.5pt dotted; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width="72">330</td><td class="xl27" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt dotted; BORDER-LEFT: windowtext 0.5pt dotted; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width="72">97</td><td class="xl27" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt dotted; BORDER-LEFT: windowtext 0.5pt dotted; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width="72">35</td><td class="xl27" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt dotted; BORDER-LEFT: windowtext 0.5pt dotted; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width="72">2.7</td><td class="xl27" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt dotted; BORDER-LEFT: windowtext 0.5pt dotted; WIDTH: 54pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width="72">12</td></tr></tbody></table>注: I 类———需要将瞬态过电压限制到特定水平的设备;       II 类———如家用电器、手提工具和类似负荷;       III 类———如配电盘、断路器,包括电缆、母线、分线盒、开关、插座等的布线系统,以及应用于工业的设备和永久接至固定装置固定安装的电动机等的一些其它设备;      IV 类———如电气计量表、波纹控制设备。2 　低压避雷器的选择 应用在低压供电系统中的低压避雷器,应从以下四个方面进行选择。 (1) 按被保护负载的特性选择低压避雷器保护电压主要考虑2 个参数:1) 冲击电压额定值Uchoe (见表2) ;2) 最大稳定的安全电压Uc 值(根据接地系统类型而定) : ·Uc > 1. 5Un(TT 和TN 系统) ·Uc > 3Un ( IT 系统) ·Uc > 1. 1Un 则保护电压应为:Uc < Up < Uchoe (Un 为额定线电压值,Up 为保护电压值)考虑低压电网接地系统的类型,通常有5 种方式:TT 系统,TN —S 系统,TN —C 系统,IT 中性线配出系统, IT 中性线不配出系统。按共模/ 差模保护方式选择低压避雷器的类型及安装接线方式,共模保护(MC) 是指相对地或中性线对地的负荷,差模保护(MD) 主要针对TT 系统和TN —S 系统,亦保护相对地负荷。如图3 所示。注:接地系统类型中第一个字母说明电源对地的关系,T 表示中性点直接接地, I 表示所有带电部分对地绝缘;第二个字母说明外露导电部分对地的关系,T 表示外露导电部分直接接地,N 表示负载采用接零保护;第三个字母表示工作零线与保护线的关系,C表示工作零线与保护零线合一,S 表示工作零线与保护线严格分开。 (2) 根据雷电密度和安装现场环境特征决定通流电流1) 雷击大地的年平均密度按下式确定:Ng = 0. 024Td1. 3式中Td ———年平均雷暴日,概括当地气象台、站资料确定(dPa) ,广州地区为87. 6dPa 。国外通常按雷电密度图选择避雷器的通流电流。我国可参考法国经验将Ng 分为三类:A 类Ng ≤0. 5 ,B 类0. 5 < Ng < 0. 6 ,C 类Ng > 1. 6。<img src="http://www.binghong3d.com/./upload_news_img/11674483019750.jpg" align="baseline" border="0" />图3 　根据接地系统选择过电压保护方式(共模或差模)2) 建筑物或半径50m 范围内安装避雷针时,低压系统需安装进线保护避雷器,最大通流电流Imax = 65kA (8P20μs) ,二次保护避雷器的最大通流电流Imax = 8～10kA。而现场无避雷针保护时,则应按地理位置及保护对象加以考虑,如表3 所示。(3) 按避雷器的最大通流电流选主分断开关,其分断容量应与系统的短路电流相匹配,采用C 型过流保护曲线,即电磁脱扣值为(5～10) In。In 为额定电流值。(4) 考虑与漏电保护设备配合:出现雷电干扰时,应首先保证重要负荷不间断供电。上级漏电保护动作值应选为300P500mA 或采用延时跳闸,下级漏电保护设备应选择高抗干扰30mA 的保护设备,以保证漏电保护的选择性跳闸。 3 　避雷器在实际应用中,应注意以下几点: (1) 根据EMC 电磁兼容性原理,低压供电系统及其负载只能一点接地,接地点应在系统的源头,并必须安装主避雷器,如图4 所示。      <div align="center"><div align="left"><table style="WIDTH: 411pt; BORDER-COLLAPSE: collapse" cellspacing="0" cellpadding="0" width="543" border="0"><colgroup><col style="WIDTH: 65pt; mso-width-source: userset; mso-width-alt: 2784" width="87" /><col style="WIDTH: 45pt; mso-width-source: userset; mso-width-alt: 1920" width="60" /><col style="WIDTH: 13pt; mso-width-source: userset; mso-width-alt: 544" width="17" /><col style="WIDTH: 32pt; mso-width-source: userset; mso-width-alt: 1376" width="43" /><col style="WIDTH: 35pt; mso-width-source: userset; mso-width-alt: 1472" span="6" width="46" /><col style="WIDTH: 11pt; mso-width-source: userset; mso-width-alt: 448" width="14" /><col style="WIDTH: 35pt; mso-width-source: userset; mso-width-alt: 1472" width="46" /></colgroup><tbody><tr style="HEIGHT: 15.75pt" height="21"><td class="xl32" style="BORDER-RIGHT: black 1pt solid; BORDER-TOP: black 1pt solid; BORDER-LEFT: black 1pt solid; WIDTH: 411pt; BORDER-BOTTOM: black 1pt solid; HEIGHT: 15.75pt; BACKGROUND-COLOR: transparent" width="543" colspan="12" height="21">居民区的</td></tr><tr style="HEIGHT: 15.75pt" height="21"><td class="xl24" style="BORDER-RIGHT: black 1pt solid; BORDER-TOP: #ffffcc 0.5pt dotted; BORDER-LEFT: black 1pt solid; WIDTH: 65pt; BORDER-BOTTOM: black 1pt solid; HEIGHT: 15.75pt; BACKGROUND-COLOR: transparent" width="87" height="21">地理位置</td><td class="xl32" style="BORDER-RIGHT: black 1pt solid; BORDER-TOP: black 1pt solid; BORDER-LEFT: black; WIDTH: 195pt; BORDER-BOTTOM: black 1pt solid; BACKGROUND-COLOR: transparent" width="258" colspan="6">城　市</td><td class="xl32" style="BORDER-RIGHT: black 1pt solid; BORDER-TOP: black 1pt solid; BORDER-LEFT: black; WIDTH: 151pt; BORDER-BOTTOM: black 1pt solid; BACKGROUND-COLOR: transparent" width="198" colspan="5">乡　村</td></tr><tr style="HEIGHT: 28.5pt" height="38"><td class="xl24" style="BORDER-RIGHT: black 1pt solid; BORDER-TOP: #ffffcc 0.5pt dotted; BORDER-LEFT: black 1pt solid; WIDTH: 65pt; BORDER-BOTTOM: black 1pt solid; HEIGHT: 28.5pt; BACKGROUND-COLOR: transparent" width="87" height="38">雷击密度(Ng)</td><td class="xl25" style="BORDER-RIGHT: black 1pt solid; BORDER-TOP: #ffffcc 0.5pt dotted; BORDER-LEFT: #ffffcc 0.5pt dotted; WIDTH: 45pt; BORDER-BOTTOM: black 1pt solid; BACKGROUND-COLOR: transparent" width="60">A</td><td class="xl35" style="BORDER-RIGHT: black 1pt solid; BORDER-TOP: black 1pt solid; BORDER-LEFT: black; WIDTH: 80pt; BORDER-BOTTOM: black 1pt solid; BACKGROUND-COLOR: transparent" width="106" colspan="3">B</td><td class="xl35" style="BORDER-RIGHT: black 1pt solid; BORDER-TOP: black 1pt solid; BORDER-LEFT: black; WIDTH: 70pt; BORDER-BOTTOM: black 1pt solid; BACKGROUND-COLOR: transparent" width="92" colspan="2">C</td><td class="xl26" style="BORDER-RIGHT: #ffffcc 0.5pt dotted; BORDER-TOP: #ffffcc 0.5pt dotted; BORDER-LEFT: #ffffcc 0.5pt dotted; WIDTH: 35pt; BORDER-BOTTOM: black 1pt solid; BACKGROUND-COLOR: transparent" width="46">A</td><td class="xl27" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt solid; BORDER-LEFT: windowtext 0.5pt solid; WIDTH: 35pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width="46">B</td><td class="xl38" style="BORDER-RIGHT: black 0.5pt solid; BORDER-TOP: black 1pt solid; BORDER-LEFT: windowtext; WIDTH: 81pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width="106" colspan="3">C</td></tr><tr style="HEIGHT: 43.5pt" height="58"><td class="xl28" style="BORDER-RIGHT: black 1pt solid; BORDER-TOP: #ffffcc 0.5pt dotted; BORDER-LEFT: black 1pt solid; WIDTH: 65pt; BORDER-BOTTOM: black 1pt solid; HEIGHT: 43.5pt; BACKGROUND-COLOR: transparent" width="87" height="58">Imax(kA) 一次进线保护</td><td class="xl25" style="BORDER-RIGHT: black 1pt solid; BORDER-TOP: #ffffcc 0.5pt dotted; BORDER-LEFT: #ffffcc 0.5pt dotted; WIDTH: 45pt; BORDER-BOTTOM: black 1pt solid; BACKGROUND-COLOR: transparent" width="60">10～15 3</td><td class="xl35" style="BORDER-RIGHT: black 1pt solid; BORDER-TOP: black 1pt solid; BORDER-LEFT: black; WIDTH: 80pt; BORDER-BOTTOM: black 1pt solid; BACKGROUND-COLOR: transparent" width="106" colspan="3">10～15</td><td class="xl35" style="BORDER-RIGHT: black 1pt solid; BORDER-TOP: black 1pt solid; BORDER-LEFT: black; WIDTH: 70pt; BORDER-BOTTOM: black 1pt solid; BACKGROUND-COLOR: transparent" width="92" colspan="2">10～15</td><td class="xl26" style="BORDER-RIGHT: #ffffcc 0.5pt dotted; BORDER-TOP: #ffffcc 0.5pt dotted; BORDER-LEFT: #ffffcc 0.5pt dotted; WIDTH: 35pt; BORDER-BOTTOM: black 1pt solid; BACKGROUND-COLOR: transparent" width="46">10～15</td><td class="xl29" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt dotted; BORDER-LEFT: windowtext 0.5pt solid; WIDTH: 35pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width="46">40</td><td class="xl41" style="BORDER-RIGHT: black 0.5pt solid; BORDER-TOP: windowtext 0.5pt solid; BORDER-LEFT: windowtext; WIDTH: 81pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width="106" colspan="3">65</td></tr><tr style="HEIGHT: 43.5pt" height="58"><td class="xl28" style="BORDER-RIGHT: black 1pt solid; BORDER-TOP: #ffffcc 0.5pt dotted; BORDER-LEFT: black 1pt solid; WIDTH: 65pt; BORDER-BOTTOM: black 1pt solid; HEIGHT: 43.5pt; BACKGROUND-COLOR: transparent" width="87" height="58">Imax (kA) 二次保护d ≥30m</td><td class="xl30" style="BORDER-RIGHT: black 1pt solid; BORDER-TOP: #ffffcc 0.5pt dotted; BORDER-LEFT: #ffffcc 0.5pt dotted; WIDTH: 45pt; BORDER-BOTTOM: black 1pt solid; BACKGROUND-COLOR: transparent" width="60">　</td><td class="xl32" style="BORDER-RIGHT: black 1pt solid; BORDER-TOP: black 1pt solid; BORDER-LEFT: black; WIDTH: 80pt; BORDER-BOTTOM: black 1pt solid; BACKGROUND-COLOR: transparent" width="106" colspan="3">　</td><td class="xl32" style="BORDER-RIGHT: black 1pt solid; BORDER-TOP: black 1pt solid; BORDER-LEFT: black; WIDTH: 70pt; BORDER-BOTTOM: black 1pt solid; BACKGROUND-COLOR: transparent" width="92" colspan="2">　</td><td class="xl31" style="BORDER-RIGHT: #ffffcc 0.5pt dotted; BORDER-TOP: #ffffcc 0.5pt dotted; BORDER-LEFT: #ffffcc 0.5pt dotted; WIDTH: 35pt; BORDER-BOTTOM: black 1pt solid; BACKGROUND-COLOR: transparent" width="46">　</td><td class="xl29" style="BORDER-RIGHT: windowtext 0.5pt solid; BORDER-TOP: windowtext 0.5pt dotted; BORDER-LEFT: windowtext 0.5pt solid; WIDTH: 35pt; BORDER-BOTTOM: windowtext 0.5pt solid; BACKGROUND-COLOR: transparent" width="46">8～10</td><td class="xl44" style="BORDER-RIGHT: black 0.5pt solid; BORDER-TOP: windowtext 0.5pt solid; BORDER-LEFT: windowtext; WIDTH: 81pt; BORDER-BOTTOM: black 1pt solid; BACKGROUND-COLOR: transparent" width="106" colspan="3">8～10</td></tr><tr style="HEIGHT: 15.75pt" height="21"><td class="xl32" style="BORDER-RIGHT: black 1pt solid; BORDER-TOP: black 1pt solid; BORDER-LEFT: black 1pt solid; WIDTH: 411pt; BORDER-BOTTOM: black 1pt solid; HEIGHT: 15.75pt; BACKGROUND-COLOR: transparent" width="543" colspan="12" height="21">3 为推荐值d = 进线保护与被保护负荷之间的距离(几个避雷器级联布置时)</td></tr><tr style="HEIGHT: 15.75pt" height="21"><td class="xl32" style="BORDER-RIGHT: black 1pt solid; BORDER-TOP: black 1pt solid; BORDER-LEFT: black 1pt solid; WIDTH: 411pt; BORDER-BOTTOM: black 1pt solid; HEIGHT: 15.75pt; BACKGROUND-COLOR: transparent" width="543" colspan="12" height="21">三产P工业系统</td></tr><tr style="HEIGHT: 30.75pt" height="41"><td class="xl24" style="BORDER-RIGHT: black 1pt solid; BORDER-TOP: #ffffcc 0.5pt dotted; BORDER-LEFT: black 1pt solid; WIDTH: 65pt; BORDER-BOTTOM: black 1pt solid; HEIGHT: 30.75pt; BACKGROUND-COLOR: transparent" width="87" height="41">连续供电的要求</td><td class="xl32" style="BORDER-RIGHT: black 1pt solid; BORDER-TOP: black 1pt solid; BORDER-LEFT: black; WIDTH: 125pt; BORDER-BOTTOM: black 1pt solid; BACKGROUND-COLOR: transparent" width="166" colspan="4">不需要</td><td class="xl32" style="BORDER-RIGHT: black 1pt solid; BORDER-TOP: black 1pt solid; BORDER-LEFT: black; WIDTH: 105pt; BORDER-BOTTOM: black 1pt solid; BACKGROUND-COLOR: transparent" width="138" colspan="3">局部</td><td class="xl32" style="BORDER-RIGHT: black 1pt solid; BORDER-TOP: black 1pt solid; BORDER-LEFT: black; WIDTH: 116pt; BORDER-BOTTOM: black 1pt solid; BACKGROUND-COLOR: transparent" width="152" colspan="4">边界</td></tr><tr style="HEIGHT: 45.75pt" height="61"><td class="xl24" style="BORDER-RIGHT: black 1pt solid; BORDER-TOP: #ffffcc 0.5pt dotted; BORDER-LEFT: black 1pt solid; WIDTH: 65pt; BORDER-BOTTOM: black 1pt solid; HEIGHT: 45.75pt; BACKGROUND-COLOR: transparent" width="87" height="61">被保护设备遭受雷击的概率</td><td class="xl32" style="BORDER-RIGHT: black 1pt solid; BORDER-TOP: black 1pt solid; BORDER-LEFT: black; WIDTH: 125pt; BORDER-BOTTOM: black 1pt solid; BACKGROUND-COLOR: transparent" width="166" colspan="4">低</td><td class="xl32" style="BORDER-RIGHT: black 1pt solid; BORDER-TOP: black 1pt solid; BORDER-LEFT: black; WIDTH: 105pt; BORDER-BOTTOM: black 1pt solid; BACKGROUND-COLOR: transparent" width="138" colspan="3">高</td><td class="xl32" style="BORDER-RIGHT: black 1pt solid; BORDER-TOP: black 1pt solid; BORDER-LEFT: black; WIDTH: 116pt; BORDER-BOTTOM: black 1pt solid; BACKGROUND-COLOR: transparent" width="152" colspan="4">很高</td></tr><tr style="HEIGHT: 28.5pt" height="38"><td class="xl24" style="BORDER-RIGHT: black 1pt solid; BORDER-TOP: #ffffcc 0.5pt dotted; BORDER-LEFT: black 1pt solid; WIDTH: 65pt; BORDER-BOTTOM: black 1pt solid; HEIGHT: 28.5pt; BACKGROUND-COLOR: transparent" width="87" height="38">雷电密度(Ng)</td><td class="xl35" style="BORDER-RIGHT: black 1pt solid; BORDER-TOP: black 1pt solid; BORDER-LEFT: black; WIDTH: 58pt; BORDER-BOTTOM: black 1pt solid; BACKGROUND-COLOR: transparent" width="77" colspan="2">A</td><td class="xl25" style="BORDER-RIGHT: black 1pt solid; BORDER-TOP: #ffffcc 0.5pt dotted; BORDER-LEFT: #ffffcc 0.5pt dotted; WIDTH: 32pt; BORDER-BOTTOM: black 1pt solid; BACKGROUND-COLOR: transparent" width="43">B</td><td class="xl25" style="BORDER-RIGHT: black 1pt solid; BORDER-TOP: #ffffcc 0.5pt dotted; BORDER-LEFT: #ffffcc 0.5pt dotted; WIDTH: 35pt; BORDER-BOTTOM: black 1pt solid; BACKGROUND-COLOR: transparent" width="46">C</td><td class="xl25" style="BORDER-RIGHT: black 1pt solid; BORDER-TOP: #ffffcc 0.5pt dotted; BORDER-LEFT: #ffffcc 0.5pt dotted; WIDTH: 35pt; BORDER-BOTTOM: black 1pt solid; BACKGROUND-COLOR: transparent" width="46">A</td><td class="xl25" style="BORDER-RIGHT: black 1pt solid; BORDER-TOP: #ffffcc 0.5pt dotted; BORDER-LEFT: #ffffcc 0.5pt dotted; WIDTH: 35pt; BORDER-BOTTOM: black 1pt solid; BACKGROUND-COLOR: transparent" width="46">B</td><td class="xl25" style="BORDER-RIGHT: black 1pt solid; BORDER-TOP: #ffffcc 0.5pt dotted; BORDER-LEFT: #ffffcc 0.5pt dotted; WIDTH: 35pt; BORDER-BOTTOM: black 1pt solid; BACKGROUND-COLOR: transparent" width="46">C</td><td class="xl25" style="BORDER-RIGHT: black 1pt solid; BORDER-TOP: #ffffcc 0.5pt dotted; BORDER-LEFT: #ffffcc 0.5pt dotted; WIDTH: 35pt; BORDER-BOTTOM: black 1pt solid; BACKGROUND-COLOR: transparent" width="46">A</td><td class="xl35" style="BORDER-RIGHT: black 1pt solid; BORDER-TOP: black 1pt solid; BORDER-LEFT: black; WIDTH: 46pt; BORDER-BOTTOM: black 1pt solid; BACKGROUND-COLOR: transparent" width="60" colspan="2">B</td><td class="xl25" style="BORDER-RIGHT: black 1pt solid; BORDER-TOP: #ffffcc 0.5pt dotted; BORDER-LEFT: #ffffcc 0.5pt dotted; WIDTH: 35pt; BORDER-BOTTOM: black 1pt solid; BACKGROUND-COLOR: transparent" width="46">C</td></tr><tr style="HEIGHT: 43.5pt" height="58"><td class="xl28" style="BORDER-RIGHT: black 1pt solid; BORDER-TOP: #ffffcc 0.5pt dotted; BORDER-LEFT: black 1pt solid; WIDTH: 65pt; BORDER-BOTTOM: black 1pt solid; HEIGHT: 43.5pt; BACKGROUND-COLOR: transparent" width="87" height="58">Imax(kA) 一次进线保护</td><td class="xl35" style="BORDER-RIGHT: black 1pt solid; BORDER-TOP: black 1pt solid; BORDER-LEFT: black; WIDTH: 58pt; BORDER-BOTTOM: black 1pt solid; BACKGROUND-COLOR: transparent" width="77" colspan="2">10～15</td><td class="xl25" style="BORDER-RIGHT: black 1pt solid; BORDER-TOP: #ffffcc 0.5pt dotted; BORDER-LEFT: #ffffcc 0.5pt dotted; WIDTH: 32pt; BORDER-BOTTOM: black 1pt solid; BACKGROUND-COLOR: transparent" width="43">10～15</td><td class="xl25" style="BORDER-RIGHT: black 1pt solid; BORDER-TOP: #ffffcc 0.5pt dotted; BORDER-LEFT: #ffffcc 0.5pt dotted; WIDTH: 35pt; BORDER-BOTTOM: black 1pt solid; BACKGROUND-COLOR: transparent" width="46">40</td><td class="xl25" style="BORDER-RIGHT: black 1pt solid; BORDER-TOP: #ffffcc 0.5pt dotted; BORDER-LEFT: #ffffcc 0.5pt dotted; WIDTH: 35pt; BORDER-BOTTOM: black 1pt solid; BACKGROUND-COLOR: transparent" width="46">10～15</td><td class="xl25" style="BORDER-RIGHT: black 1pt solid; BORDER-TOP: #ffffcc 0.5pt dotted; BORDER-LEFT: #ffffcc 0.5pt dotted; WIDTH: 35pt; BORDER-BOTTOM: black 1pt solid; BACKGROUND-COLOR: transparent" width="46">40</td><td class="xl25" style="BORDER-RIGHT: black 1pt solid; BORDER-TOP: #ffffcc 0.5pt dotted; BORDER-LEFT: #ffffcc 0.5pt dotted; WIDTH: 35pt; BORDER-BOTTOM: black 1pt solid; BACKGROUND-COLOR: transparent" width="46">65</td><td class="xl25" style="BORDER-RIGHT: black 1pt solid; BORDER-TOP: #ffffcc 0.5pt dotted; BORDER-LEFT: #ffffcc 0.5pt dotted; WIDTH: 35pt; BORDER-BOTTOM: black 1pt solid; BACKGROUND-COLOR: transparent" width="46">40</td><td class="xl35" style="BORDER-RIGHT: black 1pt solid; BORDER-TOP: black 1pt solid; BORDER-LEFT: black; WIDTH: 46pt; BORDER-BOTTOM: black 1pt solid; BACKGROUND-COLOR: transparent" width="60" colspan="2">65</td><td class="xl25" style="BORDER-RIGHT: black 1pt solid; BORDER-TOP: #ffffcc 0.5pt dotted; BORDER-LEFT: #ffffcc 0.5pt dotted; WIDTH: 35pt; BORDER-BOTTOM: black 1pt solid; BACKGROUND-COLOR: transparent" width="46">65</td></tr><tr style="HEIGHT: 43.5pt" height="58"><td class="xl28" style="BORDER-RIGHT: black 1pt solid; BORDER-TOP: #ffffcc 0.5pt dotted; BORDER-LEFT: black 1pt solid; WIDTH: 65pt; BORDER-BOTTOM: black 1pt solid; HEIGHT: 43.5pt; BACKGROUND-COLOR: transparent" width="87" height="58">Imax (kA) 二次保护d ≥30m</td><td class="xl32" style="BORDER-RIGHT: black 1pt solid; BORDER-TOP: black 1pt solid; BORDER-LEFT: black; WIDTH: 58pt; BORDER-BOTTOM: black 1pt solid; BACKGROUND-COLOR: transparent" width="77" colspan="2">　</td><td class="xl30" style="BORDER-RIGHT: black 1pt solid; BORDER-TOP: #ffffcc 0.5pt dotted; BORDER-LEFT: #ffffcc 0.5pt dotted; WIDTH: 32pt; BORDER-BOTTOM: black 1pt solid; BACKGROUND-COLOR: transparent" width="43">　</td><td class="xl25" style="BORDER-RIGHT: black 1pt solid; BORDER-TOP: #ffffcc 0.5pt dotted; BORDER-LEFT: #ffffcc 0.5pt dotted; WIDTH: 35pt; BORDER-BOTTOM: black 1pt solid; BACKGROUND-COLOR: transparent" width="46">8～10</td><td class="xl25" style="BORDER-RIGHT: black 1pt solid; BORDER-TOP: #ffffcc 0.5pt dotted; BORDER-LEFT: #ffffcc 0.5pt dotted; WIDTH: 35pt; BORDER-BOTTOM: black 1pt solid; BACKGROUND-COLOR: transparent" width="46">8～10</td><td class="xl25" style="BORDER-RIGHT: black 1pt solid; BORDER-TOP: #ffffcc 0.5pt dotted; BORDER-LEFT: #ffffcc 0.5pt dotted; WIDTH: 35pt; BORDER-BOTTOM: black 1pt solid; BACKGROUND-COLOR: transparent" width="46">8～10</td><td class="xl25" style="BORDER-RIGHT: black 1pt solid; BORDER-TOP: #ffffcc 0.5pt dotted; BORDER-LEFT: #ffffcc 0.5pt dotted; WIDTH: 35pt; BORDER-BOTTOM: black 1pt solid; BACKGROUND-COLOR: transparent" width="46">8～10</td><td class="xl25" style="BORDER-RIGHT: black 1pt solid; BORDER-TOP: #ffffcc 0.5pt dotted; BORDER-LEFT: #ffffcc 0.5pt dotted; WIDTH: 35pt; BORDER-BOTTOM: black 1pt solid; BACKGROUND-COLOR: transparent" width="46">8～10</td><td class="xl35" style="BORDER-RIGHT: black 1pt solid; BORDER-TOP: black 1pt solid; BORDER-LEFT: black; WIDTH: 46pt; BORDER-BOTTOM: black 1pt solid; BACKGROUND-COLOR: transparent" width="60" colspan="2">8～10</td><td class="xl25" style="BORDER-RIGHT: black 1pt solid; BORDER-TOP: #ffffcc 0.5pt dotted; BORDER-LEFT: #ffffcc 0.5pt dotted; WIDTH: 35pt; BORDER-BOTTOM: black 1pt solid; BACKGROUND-COLOR: transparent" width="46">8～10</td></tr></tbody></table></div><div align="left">Up :主避雷器下级的保护电压 Ups :2 次避雷器后的保护电压,短路时断开避雷器 图4 　低压供电系统避雷器安装位置</div></div><img src="http://www.binghong3d.com/./upload_news_img/11674477884110.jpg" align="baseline" border="0" />(2) 避雷器导通时刻,负载的保护电压值等于避雷器的剩余电压、连接线和断开设备的电压降之和。例如,1m 电缆的感抗约为0. 1μH ,根据Δu = LdiPdt (用8P20μs 波形) ,当电流为10kA 时,每米的峰值电压为1000V。因此,避雷器至带电导体和等电位联接点的连线如L1 、L2 、L3 尽可能短,应不超过0. 5m。 (3) 当出现高幅值雷电时,电流通过避雷器后的保护电压值也可能超过敏感设备的耐受电压值,这些设备应由二次避雷器保护。二次避雷器离主避雷器至少大于10m。如图5 所示。<img src="http://www.binghong3d.com/./upload_news_img/11674479006550.jpg" align="baseline" border="0" />图5 　两级避雷器安装举例 (4) 不论安装在何处,各避雷器应设断开设备(短路时断开) ,可以是熔断器或断路器,该类电器应与避雷器及安装点匹配(指熔断或跳闸曲线) (5) 供电系统的源头通常装设剩余电流设备。带延时或选择性的剩余电流设备可避免避雷器电流中断而产生的误动作。若避雷器安装在高灵敏度或选择性的剩余电流设备附近时,则应安装在靠近它的下侧。综上所述,正确选择和应用低压避雷器对有效抑制低压电网上因雷电产生的过电压是非常重要的,对消除和最大限度地减少过电压可能引发的灾害、使电气系统可靠实用具有重要实际意义。

332783568 发表于 2009-5-18 10:25:53

照片怎么看不到啊?

tangbo514 发表于 2009-7-25 16:10:11

why haven't picture in the document.

zengqinjiu 发表于 2011-5-30 09:42:29

,图片补充齐就好了

sefry 发表于 2011-7-1 14:13:38

谢谢你啦，好资料

osier.zhao 发表于 2011-8-17 21:39:12

zhangfl 发表于 2013-12-3 20:40:08

不错，了解了！

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低压电网防雷电过电压保护（文摘）