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觸點在通道后打開
短路電流峰值的大值，或當自然通道為零時跳閘，允許系統(tǒng)部件承受高電壓
熱應力和動態(tài)應力。為了降低這些應力，設計了限流斷路器（見1.2章“主要定義”），
能夠在短路電流出現(xiàn)之前啟動分閘操作
達到其一個峰值，并迅速熄滅觸點之間的電??；
下圖顯示了兩個預期的波浪的形狀
短路電流以及有限的短路電流。
下圖顯示了160斷路器中Tmax XT2L160的極限曲線。x軸顯示了對稱前景的有效值
短路電流，而y軸顯示相對峰值。極限
可以通過比較對稱故障的相同值來評估影響
電流，與預期短路電流對應的峰值
（曲線A）具有有限峰值（曲線B）。
預期的
短路電流
有限的
短路電流
ABB |保護和控制裝置91
2一般特征
1SDC00012F0001
考慮到電動應力和由此產(chǎn)生的機械應力
應力與電流峰值密切相關，使用電流限制
斷路器允許電氣系統(tǒng)中部件的佳尺寸
植物此外，還可以使用電流限制來獲得后備保護
在兩個串聯(lián)斷路器之間。
2.3極限曲線
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
曲線A
曲線B
In=20
斷路器XT2L160，在400 V時具有20個熱磁脫扣器，用于
故障電流為90 kA，將短路峰值僅限制在14.6 kA，與沒有限制的峰值相比顯著降低
（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).
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