低压配电线路中最严重的故障当属短路故障，它会对整个系统带来极其严重的破坏。各级断路器即用来保证短路故障发生时快速切断故障电流，以保护故障点和前端电源设备的一种重要装置。当线路内发生短路故障时断路器也是首当其冲容易受伤，所以在设计整套低压配电系统时，会将低压断路器短路分断能力作为一项重要指标来对待。
短路发生瞬间电流波形图
断路器短路分断能力包含两个概念：
一、运行短路分断能力Ics(线路中短路电流低于此值，断路器可有效断开，且断路器不会失效可重复合闸使用)
二、极限短路分断能力Icu(线路中短路电流低于此值高于Ics，断路器可有效断开，但断路器内部机构很可能会变形失效。高于此值时断路器极有可能触点熔焊不能断开)
综上两条，断路器短路分断能力越高越好，但是价格也是水涨船高。考虑到材料成本，设计低压配电系统时，往往会根据各级电路的预计最大短路电流来配合选用相应满足条件的断路器。
理论上来讲变压器出线端可能出现的短路电流最大，因为出线端没有输电线路的电阻，只有变压器内阻。所以在选择变压器出口位置的总断路器时，需根据变压器铭牌上的额定电流值和阻抗值来计算预期短路电流，计算方法是(变压器阻抗的倒数乘以变压器额定电流)如一个630kVA变压器，阻抗率4%，额定电流903A。那么其低压侧短路电流=(1/0.04)*903=22.5kA，我们选断路器的时候就要选Ics大于22.5kA。
干式树脂绝缘电力变压器
油浸电力变压器
随着变压器容量不断增大，新技术新材料运用到变压器上使其阻抗率减小，线路中预期短路电流越来越大，现在框架断路器极限短路分断能力已经达到了150kA级别，常用50kA、65kA。
塑壳断路器
由于用电线路的延长，线路内阻逐渐加大，越是远离变压器出口位置最大短路电流就是逐渐减小，所以到了第二级断路器(多数为塑壳断路器)分断能力需求逐渐减小，一般最高为70kA,到了终端用电器的塑壳断路器最小可以使用到25kA级别。
微型断路器
住户内的微型断路器多选用4.5kA或6kA即可满足使用需求。工业用途位置使用的微型断路器多数选用高分断能力的10kA级别。
总结：断路器短路分断能力规格选择也要遵循由进线到负载逐级递减的原则，以防出现故障时越级烧坏断路器的情况，扩大故障影响面。
河南博泰电力工程有限公司作为河南地区规模较大的电力安装公司，以“诚信高效、团结进取、品质优良、售后完善”的经营理念，为顾客打造优质的工程，最大限度满足客户需求。
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