Conventional and digital busbar protection: a comparative reliability study

Digital protection based on numerical principles is increasingly being applied to major power system networks. One application where such relays have not been applied is 275 kV and 400 kV busbar protection. This paper describes a series of reliability studies which have been performed on two digital busbar protection schemes. Comments are given on dependability and security aspects of reliability and details of the data sources, methods of analysis and a summary of the results are provided. The paper concludes by discussing the implications of the reliability studies