An enhanced decentralised numerical busbar protection relay utilising instantaneous current values from high speed sampling

The world´s first decentralised numerical busbar protection relay was developed in 1989 and put into service in one of Tokyo Electric Power Company´s, (TEPCO) EHV substations. Since then several sets of this busbar protection have been installed in practical applications in 500 kV and 275 kV substations. In 1997 an actual busbar fault occurred at one of these substations and it was possible to obtain relay operational data. More recently, an improved decentralised system was developed utilizing high performance MPUs, enhanced signal processing and also the more recent developments in communication technologies. In this paper we briefly introduce our experience in the field of numerical busbar protection followed by details of the configuration of the new system. A description of the design considerations that led to the improvements that were implemented is also included