. Opening solenoid Load Circuit-breaker Protective conductor L1 L2 L3 N PE Generic distribution system (IT, TT, TN) ASDC008002F0201 1.3.3 RESIDUAL CURRENT DEVICES The residual current releases are associated with the circuit-breaker in order to obtain two main functions in a single device: - protection against overloads and short-circuits; - protection against indirect contacts (presence of voltage on exposed conductive parts due to loss of insulation). Besides, they can guarantee an additional protection against the risk of fire deriving from the evolution of small fault or leakage currents which are not detected by the standard protections against overload. Residual current devices having a rated residual current not exceeding 30 mA are also used as a means for additional protection against direct contact in case of failure of the relevant protective means. Their logic is based on the detection of the vectorial sum of the line currents through an internal or external toroid. This sum is zero under service conditions or equal to the earth fault current (I∆) in case of earth fault.When the release detects a residual current different from zero, it opens the circuit-breaker through an opening solenoid. As we can see in the picture the protection conductor or the equipotential conductor have to be installed outside the eventual external toroid.Generic distribution system (IT, TT, TN) ASDC008002F0201 1.3.3 RESIDUAL CURRENT DEVICES The residual current releases are associated with the circuit-breaker in order to obtain two main functions in a single device: - protection against overloads and short-circuits; - protection against indirect contacts (presence of voltage on exposed conductive parts due to loss of insulation). Besides, they can guarantee an additional protection against the risk of fire deriving from the evolution of small fault or leakage currents which are not detected by the standard protections against overload. Residual current devices having a rated residual current not exceeding 30 mA are also used as a means for additional protection against direct contact in case of failure of the relevant protective means. Their logic is based on the detection of the vectorial sum of the line currents through an internal or external toroid. This sum is zero under service conditions or equal to the earth fault current (I∆) in case of earth fault. The operating principle of the residual current release makes it suitable for the distribution systems TT, IT (even if paying particular attention to the latter) and TN-S, but not in the systems TN-C. In fact, in these systems, the neutral is used also as protective conductor and therefore the detection of the residual current would not be possible if the neutral passes through the toroid, since the vectorial sum of the currents would always be equal to zero.

断开电磁阀负载断路器保护导体L1 L2 L3 N PE通用配电系统（IT、TT、TN）ASDC008002F0201 1.3.3剩余电流装置剩余电流释放装置与断路器相关，以便在单个装置中实现两个主要功能：-过载和短路保护；-防止间接接触（由于绝缘损失，外露导电部件上存在电压）。此外，它们还可以保证额外的保护，防止因小型故障或泄漏电流的演变而引发火灾的风险，而这些故障或泄漏电流是标准过载保护无法检测到的。额定剩余电流不超过30 mA的剩余电流装置也可用作在相关保护装置失效时防止直接接触的额外保护装置。它们的逻辑是基于通过内部或外部圆环检测线电流的矢量和。在工作条件下，该总和为零或等于接地故障电流（I∆) 如果发生接地故障。当释放装置检测到与零不同的剩余电流时，它通过一个断开电磁阀断开断路器。正如我们在图中所看到的，保护导体或等电位导体必须安装在终的外部圆环的外部。通用配电系统（IT、TT、TN）ASDC008002F0201 1.3.3剩余电流装置剩余电流脱扣器与断路器相关，以便在单个装置中实现两个主要功能：-过载和短路保护；-防止间接接触（由于绝缘损失，外露导电部件上存在电压）。此外，它们还可以保证额外的保护，防止因小型故障或泄漏电流的演变而引发火灾的风险，而这些故障或泄漏电流是标准过载保护无法检测到的。额定剩余电流不超过30 mA的剩余电流装置也可用作在相关保护装置失效时防止直接接触的额外保护装置。它们的逻辑是基于通过内部或外部圆环检测线电流的矢量和。在工作条件下，该总和为零或等于接地故障电流（I∆) 如果发生接地故障。剩余电流释放的工作原理使其适用于配电系统TT、it（即使特别注意后者）和TN-S，但不适用于系统TN-C。事实上，在这些系统中，中性点也用作保护导体，因此，如果中性点通过圆环，则无法检测剩余电流，因为电流的矢量和总是等于零。