Study On Statistically Reliability Assessmentand Its Application

To assess the reliability of transmission system comprehensively and objectively can provide more scientific reliability information for grid planning and operation and is thus significant for improving the reliability of a power system. Nowadays, in China the reliability of the transmission system is evaluated only according to"Reliability Evaluation Code for Transmission and Distribution Facilities", which is based on"the view of equipment". Besides the equipment, however, the grid structure can also affect the system reliability tangibly, therefore, it has become necessary to access the reliability on a"system-wide view", either.This paper analyzes the development trend of reliability performance indices of the transmission system based on the research on current situation of foreign statistically reliability assessment and proposes circuit analysis based and connection point analysis based statistically reliability assessment which reflect the network availability and power supply continuity respectively from the view of functional equipment group and transmission system customers combined with the current operating status of the transmission system including statistical criteria, indices and their meanings, etc. These two kinds of assessment methods can be combined with the traditional method when applied into practice to gain more comprehensive reliability information of the system.In order for the assessment methods proposed to be better brought into practice, the paper raises the algorism and its technical process according to the definition of circuit and connection point and shows its effectiveness through searching for the circuits and connection points in a practical transmission system. At the same time, the paper statistically assesses the reliability information of some part of a practical transmission system through the method proposed combined with the original assessment method already applied so as to prove the effectiveness of the methods.Moreover, this paper applies the data gained from the circuit analysis based statistically reliability assessment into the reliability predictive analysis of the transmission system through the construction of the state space of the circuits. This paper proposed a reliability evaluation model of transmission system based on circuit analysis in which the states of dispatching reserve shutdown and passive reserve shutdown other than forced outage and planed outage are put into consideration. Besides, this method also emphasizes the treatment of the condition that one terminal of a bus might fall into an outage in some modes of connection. This paper evaluates the reliability of a practical network to prove the effectiveness of this method.