Reliability Modeling Of Relay Protection And Its Application Based On The Dynamic Fault Tree

The power grid is developing very fast as the development of social economy. The project of "transmitting power from west to east" and large capacity power transmission over long distance of (EHV) UHV have made the power grids interconnection become inevitable. As the increasing complexity of the power grid structure and its growing scale, relay protection device become more and more important in eliminating faults quickly and preventing accident from enlargement. The reliable action of relay protection device has an important effect on the safe and secure operation of power system. Therefore how to improve the reliability of relay protection device and build reliability model that is adapt to the development of the relay protection become the major issues for the power system researchers.In this thesis, the influencing factors for the reliability of relay protection devices have been studied and a mathematical model that is adapt to the safety and reliability of relay protection devices is established. This mathematical model has been applied to assess the reliability of existing relay protection device. The main contents of the thesis can be summarized as below.Firstly, on the basis of the existing theoretical methods for calculating the reliability, the calculating methods for the reliability indexes of relay protection devices are chosen.Secondly, taking all influencing factors in safe operation of relay protection system into account, the influencing factors are classified and sorted. Then software model, hardware model, secondary circuit model and human factor model for relay protection device are constructed respectively. By applying these models, a reliability structure diagram of relay protection system is obtained.Thirdly, a new reliability assessment method is presented. Dynamic Fault Tree is used in the reliability assessment of relay protection system. The Dynamic Fault Tree reliability model has been established in the thesis, in which the influences of TA/TV, channel, auxiliary devices, secondary circuit etc. are considered. By applying this model, we can calculate many indexes of single relay protection device such as the total health of the device, failure rate and mean time to repair.Forthly, the proposed assessment method is applied in some types of220kV line protection devices in Taizhou city. By comparing the evaluation data and actual statistics data, the validity of this mathematical model has been verified.