Classification: According to the action mode, the electromagnetic residual current protector is classified as 2.1.1. The output voltage of the secondary circuit of the zero sequence current transformer is not amplified and directly excites the residual current release, which is called the electromagnetic residual current protector. Its action function is independent of the line voltage 1.2 Electronic residual current protection device: An electronic amplification circuit is connected between the secondary circuit of the zero sequence current transformer and the release device. The output voltage of the secondary circuit of the transformer is amplified by the electronic circuit and then excites the residual current release device, which is called an electronic residual current protection device. Its action function is related to the line voltage. According to the functions of residual current protectors, 2.1 residual current circuit breakers are mechanical switching devices that detect residual current, compare the residual current value with the reference value, and disconnect the main circuit contact when the residual current value exceeds the reference value. The residual current circuit breaker is equipped with overload and short circuit protection, and some residual current circuit breakers can also be equipped with overvoltage protection 2.2 Residual Current Relay Residual current relay is an electrical device that detects residual current, compares the residual current value with the reference value, and sends a mechanical opening and closing signal when the residual current value exceeds the reference value, causing the mechanical switch electrical device to trip or the sound and light alarm device to give an alarm. Residual current relays are often combined with AC contactors or low-voltage circuit breakers to form residual current protectors, which are used as the main protection switch or branch protection switch for rural low-voltage power grids 2.3 Mobile residual current protection device Mobile residual current protection device is an electrical appliance composed of plugs, residual current protection devices, and sockets or wiring devices. It includes residual current protection plugs, mobile residual current protection sockets, residual current protection plug socket converters, etc., used to provide leakage protection for mobile electrical equipment 2.4 Fixed installed residual current protection sockets are electrical appliances composed of fixed sockets and residual current protection devices, which can also provide leakage protection for mobile electrical equipment. Table 1 Comparison of Performance between Electromagnetic and Electronic Residual Current Protectors Based on the Usage of Residual Current Protectors. 2. 3.1 Residual Current Protectors Used by Professional Personnel. These residual current protectors are generally rated at a high current and are used as protective switches for main or branch lines in power distribution devices. If a fault occurs, the range of impact is relatively large, requiring professional personnel to install, use, and maintain them. Residual current relays and high current residual current circuit breakers belong to this form of residual current protection 3.2 Residual current protectors for household and similar purposes are used as residual current protectors in commercial, office buildings, and urban and rural residential buildings. Generally, the rated current is relatively small, and as leakage protection devices for terminal electrical circuits, they are suitable for use by non professionals. Mainly household residual current circuit breakers and mobile residual current protectors. According to the operating time of residual current protectors, it can be divided into 4.1 general residual current protectors. Residual current protectors with no fault delay are mainly used as leakage protection devices for branch and terminal lines 4.2 Delayed residual current protector is a residual current protector specifically designed to achieve a predetermined limit of non operating time for a certain residual operating current value. Delayed residual current protectors are mainly used as protection devices for main or branch lines, and can be combined with protection devices for terminal lines to meet the requirements of selective protection
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