Reliability Assessment Of Protection System In Smart Substation

Under the initiative of the State Grid Corporation to establish a “strong smart grid”,smart substations based on the power industry standard IEC61850 have been rapidly developed and widely used.A large number of intelligent electronic devices have been put into use,which has brought about tremendous changes in the signal acquisition methods,communication methods of smart substation protection devices.Under the background of development,the research on the reliability of smart substation protection system will have important practical significance for the safe and stable operation of smart substation.The traditional reliability assessment methods and evaluation models can not fully reflect the operating status of the protection system in different periods.Therefore,the time-varying reliability assessment of the smart substation protection system is gradually attracting people's attention.This paper studies two aspects of reliability assessment and state assessment of smart substation protection system,and provides theoretical basis for the operation and maintenance of smart substation protection system in the future engineering practice.This paper studies the reliability changes of various protection systems of smart substations considering planned maintenance.According to the improvement effect of maintenance on the operating state of the protection equipment and the aging phenomenon of the equipment itself changing with time,the failure rate model of the protection system related equipment based on Weibull distribution is established.According to the typical structure of each protection system in different sampling trip modes,combined with the logical relationship of the relevant protection devices in each protection system,the reliability block diagram is drawn.Using the reliability block diagram method to obtain the time-varying model of the failure rate of each protection system,and according to the mathematical relationship between each reliability evaluation index and the failure rate,the reliability evaluation model of each protection system of smart substation under different sampling trip modes is obtained.In this paper,according to the phenomenon that the failure rate of each protection system considering planned maintenance and equipment aging has different characteristics at different stages,different maintenance and repair cycles are adopted for each protection system in the stable operation period and the loss period.The maintenance operation cost and reliable running time of the substation protection equipment determine the annual running cost of the smart substation protection system under different sampling trip modes.According to the principle of the lowest annual average operating cost,the optimal planned maintenance period of the protection system of the smart substation in the stable operation period and the loss period under different sampling trip modes is determined.This paper analyzes the smart substation configuration description SCD file,obtains the alarm signal of each protection device in the protection system,constructs the protection function failure fault tree,and reflects the reasons for the failure of each protection function in the protection system.The alert signal from the protection system related device is associated with the underlying event of the failed fault tree.PAT is used to formally model the process of protection functions of each protection system and its working conditions,and the interaction model between IEDs.The PAT is used to simulate the interaction behavior of the protection system under the action of each alarm signal,and the accessibility of the protection system function are verified.