The HNDL series residual current electrical fire monitoring detector (hereinafter referred to as the detector) is mainly used in AC 50Hz, rated working voltage 380V distribution systems to prevent electrical fires caused by residual current and other factors. It also has the function of measuring various electrical parameters (residual current) of the power supply line and can monitor the status of the line in real time. The product has complete performance and high degree of automation, suitable for electrical safety and fire prevention in home residences, residential buildings, offices, trade malls, small shops, public cultural and entertainment venues, restaurants and tourism, collective dormitories, schools, cultural relics protection units, etc.