The invention provides a TT, TN distribution system (800, 810, 820). The distribution system (800, 810, 820) is provided with at least one protective device (100-1, 100-21, 100-22...) and at least oneelectronic controller, and is characterized in that a power supply of the electronic controller is obtained from the distribution system (800, 810, 820), at least one current collector (300) is arranged on N lines corresponding to the protective device (100-1, 100-21, 100-22...), and the rated current value of the current collector (300) is not greater than 20% of the rated current of the N line.The protective device disclosed by the invention realizes the functions of detecting and protecting N line breakage under the condition of three-phase current unbalance which causes damage to a loadand will affect the normal operation of the load, thereby enabling the protection function setting of the protective device to be more scientific, reasonable and perfect, and enabling the operation ofthe power grid to be safer. Meanwhile, the TT, TN distribution system achieves the goal of enabling the traditional electric power protection device to have the above functions at a low cost, therebyhaving an extremely high cost-performance ratio.