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兩個或多個過電流保護裝置的工作特性
這樣，當過電流發(fā)生在規(guī)定的限制范圍內時，打算在這些限制范圍內運行的設備會這樣做，而其他設備不會運行。”
（IEC 60947-1，定義2.5.23）；
可以區(qū)分：
•完全歧視，這意味著“過電流歧視
在兩個過流保護裝置串聯(lián)的情況下，保護裝置
在負載側提供保護，而不會使另一個保護裝置跳閘
裝置”（IEC 60947-2，定義2.17.2）；
•部分歧視，即“過電流歧視，導致
在兩個過流保護裝置串聯(lián)的情況下，保護裝置
在負載側提供高達給定過電流限制的保護，而無需
另一個跳閘”（IEC 60947-2，定義2.17.3）；該過電流閾值為
稱為“鑒別極限電流為
“（IEC 60947-2，定義2.17.4）。
當前歧視
這種類型的判別是基于觀察到斷層越近
到達網(wǎng)絡饋線時，短路電流將越大。我們
因此，只需通過校準即可定位故障發(fā)生的區(qū)域
裝置上游的瞬時保護達到極限值高于
導致下游裝置跳閘的故障電流。
我們通常只能在特定情況下實現(xiàn)完全歧視
故障電流不是很高（與設備的額定電流相當）或
如果高阻抗部件位于兩個保護裝置之間
（例如變壓器、很長或很小的電纜……）產生巨大差異
短路電流值之間。
因此，這種協(xié)調主要在終分配中是可行的
網(wǎng)絡（具有低額定電流和短路電流值以及高
連接電纜的阻抗）。
研究中通常使用裝置的時間-電流跳閘曲線。
該解決方案是：
•快速；
•易于實施；
•價格低廉。
另一方面：
•歧視限制通常較低；
•提高識別級別導致設備尺寸快速增長。
以下示例顯示了基于電流判別的典型應用
關于斷路器的不同瞬時跳閘閾值
考慮過的。
of the operating characteristics of two or more over-current protective devices such that, on the incidence of over-currents within stated limits, the device intended to operate within these limits does so, while the others do not operate” (IEC 60947-1, def. 2.5.23); It is possible to distinguish between: • total discrimination, which means “over-current discrimination such that, in the case of two over-current protective devices in series, the protective device on the load side provides protection without tripping the other protective device” (IEC 60947-2, def. 2.17.2); • partial discrimination, which means “over-current discrimination such that, in the case of two over-current protective devices in series, the protective device on the load side provides protection up to a given over-current limit without tripping the other” (IEC 60947-2, def. 2.17.3); this over-current threshold is called “discrimination limit current Is ” (IEC 60947-2, def. 2.17.4). Current discrimination This type of discrimination is based on the observation that the closer the fault comes to the network’s feeder, the greater the short-circuit current will be. We can therefore pinpoint the zone where the fault has occurred simply by calibrating the instantaneous protection of the device upstream to a limit value higher than the fault current which causes the tripping of the device downstream. We can normally achieve total discrimination only in specific cases where the fault current is not very high (and comparable with the device’s rated current) or where a component with high impedance is between the two protective devices (e.g. a transformer, a very long or small cable...) giving rise to a large difference between the short-circuit current values. This type of coordination is consequently feasible mainly in final distribution networks (with low rated current and short-circuit current values and a high impedance of the connection cables). The devices’ time-current tripping curves are generally used for the study. This solution is: • rapid; • easy to implement; • and inexpensive. On the other hand: • the discrimination limits are normally low; • increasing the discrimination levels causes a rapid growing of the device sizes. The following example shows a typical application of current discrimination based on the different instantaneous tripping threshold values of the circuit-breakers considered.
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