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在沒有接地故障的情況下，電流的矢量和I? 等于零；
如果發(fā)生接地故障? 值超過額定剩余工作電流
我
?N
，位于圓環(huán)體二次側(cè)的電路向
導(dǎo)致斷路器跳閘的專用分閘線圈。
可根據(jù)故障類型對(duì)RCD進(jìn)行一次分類
它們可以檢測到的電流：
-交流型：確保剩余正弦交流電跳閘，
是否突然施加或緩慢上升；
-A型：確保剩余正弦交流電跳閘，以及
剩余脈動(dòng)直流電，無論是突然施加還是緩慢上升；
-B型：確保剩余直流電流跳閘，剩余正弦電流跳閘
交流電和剩余脈動(dòng)直流電，無論是否突然
應(yīng)用或緩慢上升。
操作延時(shí)的另一種分類是：
-未播放類型；
-延時(shí)S型。
圖1：剩余電流裝置的工作原理
4.7剩余電流裝置（RCD）
ABB |電氣設(shè)備457
4保護(hù)人類
我? 我?
我? 0.3安
t 0.5秒
我? 0.3安
t 0.5秒
RCD可以與其他設(shè)備耦合，也可以不耦合；可以區(qū)分
其中：
-純剩余電流斷路器（RCCB）：它們只有
電流釋放，只能防止接地故障。它們必須耦合
帶熱磁斷路器或保險(xiǎn)絲，用于防止
熱應(yīng)力和動(dòng)應(yīng)力；
-帶過流保護(hù)的剩余電流斷路器（RCBO）：它們
是熱磁斷路器和RCD的組合；為了這個(gè)
原因是，它們提供過電流和接地保護(hù)
故障電流；
-外環(huán)形剩余電流斷路器：用于工業(yè)
具有高電流的植物。它們由連接到
帶繞組的外圓環(huán)，用于檢測剩余電流；萬一
接地故障時(shí)，信號(hào)指令斷路器的斷開機(jī)構(gòu)
或線路接觸器。
給定I?N
運(yùn)行剩余電流是剩余電流的一個(gè)重要參數(shù)
電流器件是剩余的非工作電流，代表
不引起斷路器的剩余電流的大值
旅行等于0.5 I?N
因此，可以得出以下結(jié)論：
-對(duì)于I? < 0.5⋅我
?N
RCD不得運(yùn)行；
-對(duì)于0.5⋅我
?N
<我? < 我?N
RCD可以運(yùn)行；
-對(duì)于I? > 我?N
RCD應(yīng)運(yùn)行。
對(duì)于額定工作剩余電流的選擇，有必要考慮：，
除了與接地系統(tǒng)協(xié)調(diào)外，還包括
電廠泄漏電流；每個(gè)相位上的矢量和不得為
大于0.5⋅我
?N
以避免意外跳閘。

In absence of an earth fault, the vectorial sum of the currents I? is equal to zero; in case of an earth fault if the I? value exceeds the rated residual operating current I ?n , the circuit at the secondary side of the toroid sends a command signal to a dedicated opening coil causing the tripping of the circuit-breaker. A first classification of RCDs can be made according to the type of the fault current they can detect: - AC type: the tripping is ensured for residual sinusoidal alternating currents, whether suddenly applied or slowly rising; - A type: tripping is ensured for residual sinusoidal alternating currents and residual pulsating direct currents, whether suddenly applied or slowly rising; - B type: tripping is ensured for residual direct currents, for residual sinusoidal alternating currents and residual pulsating direct currents, whether suddenly applied or slowly rising. Another classification referred to the operating time delay is: - undelayed type; - time delayed S-type. Figure 1: Operating principle of the residual current device 4.7 Residual current devices (RCDs) ABB | Electrical devices 457 4 Protection of human beings I? I? I? 0.3 A t 0.5 s I? 0.3 A t 0.5 s RCDs can be coupled, or not, with other devices; it is possible to distinguish among: - pure residual current circuit-breakers (RCCBs): they have only the residual current release and can protect only against earth fault. They must be coupled with thermomagnetic circuit-breakers or fuses, for the protection against thermal and dynamical stresses; - residual current circuit-breakers with overcurrent protection (RCBOs): they are the combination of a thermomagnetic circuit-breaker and a RCD; for this reason, they provide the protection against both overcurrents as well as earth fault current; - residual current circuit-breakers with external toroid: they are used in industrial plants with high currents. They are composed by a release connected to an external toroid with a winding for the detection of the residual current; in case of earth fault, a signal commands the opening mechanism of a circuit-breaker or a line contactor. Given I?n the operating residual current, a very important parameter for residual current devices is the residual non-operating current, which represents the maximum value of the residual current which does not cause the circuit-breaker trip; it is equal to 0.5 I?n . Therefore, it is possible to conclude that: - for I? < 0.5⋅I ?n the RCD shall not operate; - for 0.5⋅I ?n < I? < I?n the RCD could operate; - for I? > I?n the RCD shall operate. For the choice of the rated operating residual current, it is necessary to consider, in addition to the coordination with the earthing system, also the whole of the leakage currents in the plant; their vectorial sums on each phase shall not be greater than 0.5⋅I ?n in order to avoid unwanted tripping.