A failure pervasion model was founded-fuzzy probability Petri net(FPPN)model which depicts the propagation and pervasion relation among failures,then failure pervasion intensity was introduced,the process of failure pervasion was depicted based on k-step fault pervasion principle and the pervasion intensity was expressed by a number.

For reliability assessment of complex distribution system a new method is presented based on the fault pervasion of the multilevel B-C-N-M region sub-networks.

A novel reliability evaluation method aiming at the load point reliability indices is proposed for complicated distribution systems based on combination of the minimal-path method and the fault-spreading-method.

The rationale of failure intensity of heat-supply network is analyzed based on the reliability theory, the analysis is made on determining the principle and the method of failure intensity value of heat-supply network, and measures for decreasing failures of heat-supply network are put forward.

Subsequently,the grade diffusing process was described combining with the failure pervasion intensity,and the failure propagation paths and relevant key nodes with high pervasion ability were found with t.