触点在通道后打开
短路电流峰值的大值，或当自然通道为零时跳闸，允许系统部件承受高电压
热应力和动态应力。为了降低这些应力，设计了限流断路器（见1.2章“主要定义”），
能够在短路电流出现之前启动分闸操作
达到其一个峰值，并迅速熄灭触点之间的电弧；
下图显示了两个预期的波浪的形状
短路电流以及有限的短路电流。
下图显示了160断路器中Tmax XT2L160的极限曲线。x轴显示了对称前景的有效值
短路电流，而y轴显示相对峰值。极限
可以通过比较对称故障的相同值来评估影响
电流，与预期短路电流对应的峰值
（曲线A）具有有限峰值（曲线B）。
预期的
短路电流
有限的
短路电流
ABB |保护和控制装置91
2一般特征
1SDC00012F0001
考虑到电动应力和由此产生的机械应力
应力与电流峰值密切相关，使用电流限制
断路器允许电气系统中部件的佳尺寸
植物此外，还可以使用电流限制来获得后备保护
在两个串联断路器之间。
2.3极限曲线
Ip[kA]
1000
198千安
100
14.6千安
10
1.
1.00 10.00 100.00
x均方根[kA]
1000
曲线A
曲线B
In=20
断路器XT2L160，在400 V时具有20个热磁脱扣器，用于
故障电流为90 kA，将短路峰值仅限制在14.6 kA，与没有限制的峰值相比显著降低
（198 kA）。

the opening of the contacts occurs after the passage of the peak of the short-circuit current, or in which the trip occurs with the natural passage to zero, allows the system components to be subjected to high stresses, of both thermal and dynamic type. To reduce these stresses, currentlimiting circuit-breakers have been designed (see Chapter 1.2 “Main definitions”), which are able to start the opening operation before the short-circuit current has reached its first peak, and to quickly extinguish the arc between the contacts; the following diagram shows the shape of the waves of both the prospective short-circuit current as well as of the limited short-circuit current. The following diagram shows the limit curve for Tmax XT2L160, In160 circuitbreaker. The x-axis shows the effective values of the symmetrical prospective short-circuit current, while the y-axis shows the relative peak value. The limiting effect can be evaluated by comparing, at equal values of symmetrical fault current, the peak value corresponding to the prospective short-circuit current (curve A) with the limited peak value (curve B). Prospective short-circuit current Limited short-circuit current ABB | Protection and control devices 91 2 General characteristics 1SDC008012F0001 Considering that the electro-dynamic stresses and the consequent mechanical stresses are closely connected to the current peak, the use of current limiting circuit-breakers allows optimum dimensioning of the components in an electrical plant. Besides, current limitation may also be used to obtain back-up protection between two circuit-breakers in series. 2.3 Limitation curves Ip [kA] 1000 198 kA 100 14.6 kA 10 1 1.00 10.00 100.00 x rms [kA] 1000.00 Curve A Curve B In=20 Circuit-breaker XT2L160 with thermomagnetic release In 20 at 400 V, for a fault current of 90 kA, limits the short-circuit peak to 14.6 kA only, with a remarkable reduction compared with the peak value in the absence of limitation (198 kA).