One of the main characteristics of a residual current release is its minimum rated residual current I∆n . This represents the sensitivity of the release. According to their sensitivity to the fault current, the residual current circuitbreakers are classified as: - type AC: a residual current device for which tripping is ensured in case of residual sinusoidal alternating current, in the absence of a dc component whether suddenly applied or slowly rising; - type A: a residual current device for which tripping is ensured for residual sinusoidal alternating currents in the presence of specified residual pulsating direct currents, whether suddenly applied or slowly rising. - type B residual current device for which tripping is ensured for residual sinusoidal alternating currents in presence of specified residual pulsanting direct currents whether suddenly applied or slowy rising, for residual directs may result from rectifying circuits.In presence of electrical apparatuses with electronic components (computers, photocopiers, fax etc.) the earth fault current might assume a non sinusoidal shape but a type of a pulsating unidirectional dc shape. In these cases it is necessary to use a residual current release classified as type A. In presence of rectifying circuits (i.e. single phase connection with capacitive load causing smooth direct current, three pulse star connection or six pulse bridge connection, two pulse connection line-to-line) the earth fault current might assume a unidirectional dc shape. In this case it is necessary to use a residual current release classified as type B.

剩余电流脱扣器的主要特征之一是其小额定剩余电流I∆N这代表了释放的敏感性。根据其对故障电流的敏感性，剩余电流断路器被分类为：-AC型：在没有直流分量（无论是突然施加还是缓慢上升）的情况下，在剩余正弦交流电的情况下确保跳闸的剩余电流装置；-A型：一种剩余电流装置，在存在规定的剩余脉冲直流电（无论是突然施加还是缓慢上升）的情况下，确保剩余正弦交流电跳闸。-B类剩余电流装置，在存在规定的剩余脉冲直流电（无论是突然施加还是缓慢上升）的情况下，确保剩余正弦交流电跳闸，因为剩余直流电可能由整流电路产生。在有电子元件（计算机、复印机、传真机等）的电气设备的情况下，接地故障电流可能呈现非正弦形状，但属于脉动单向直流形状。在这些情况下，有必要使用分类为a型的剩余电流释放装置。在存在整流电路的情况下（即与电容性负载的单相连接导致平滑直流、三脉冲星形连接或六脉冲桥式连接、两脉冲线对线连接），接地故障电流可能呈现单向直流形状。在这种情况下，有必要使用分类为B型的剩余电流脱扣器。