Abstract: In distribution network， the equipments in different regions have different reliabilities， and the automation of fault diagnosis is at low level. In order to make the fault diagnosis quick and accurate，a new method of distribution network fault diagnosis was presented based on improved time fuzzy Petri net. Firstly， the information of breakers with the switch and electrical information were corrected，and the areas where power collapse were found out. Then， according to the range that the breaker can protect， the suspicious fault elements were found out， and the time fuzzy Petri net model for suspicious fault elements with time-tag information was built.Finally the diagnosis results were given. The simulation results show that the efficiency and accuracy of fault diagnosis are improved. In addition， the fault process can be shown for dispatchers with good practical application value.

Key words: time fuzzy, Petri net, alarms information, fault diagnosis, distribution network