Study on artificial immune mechanism for distribution network fault diagnosis with large scale renewable energy integration

Single phase grounding fault is the most common fault in distribution system. It mostly occurs in wet and rainy weather, which is caused by many factors, such as tree barrier, single-phase breakdown of distribution line insulator, single-phase disconnection, small animal harm and so on. Single phase grounding not only affects the normal power supply of users, but also may produce overvoltage, burn equipment, and even cause phase to phase short circuit, expanding the scope of accidents. The 10-35kV lines in China's urban power grid are mainly neutral non effective grounding systems. After the occurrence of single-phase grounding fault, the fault characteristic signal is weak and difficult to extract, resulting in the difficulty of accurate fault diagnosis. However, due to the limitations of the traditional fault diagnosis principle relying on the zero sequence voltage and current criterion, there are serious misjudgments and omissions in the single-phase grounding fault diagnosis of distribution network. With the rapid development of distribution network in recent years, the functions of wave recording and event playback of distribution automation system and its equipment can collect online power grid operation information before and after. After the accident, a sample database of accident cases shall be formed. How to use these data to improve the