Itsuo Shuto

Field experience and assessment of GPS signal receiving and distribution system for synchronizing power system protection, control and monitoring

This paper describes the field experience and assessment of a GPS signal receiving and distribution system for synchronizing power system protection, control and monitoring. Application of GPS synchronization to protection, control and monitoring systems is becoming more popular in the field of power systems. However, the actual performance and reliability of GPS signal receipt within the substation environment has not been comprehensively assessed. This paper includes the system configuration for GPS synchronization, the results of our assessment of GPS synchronizing signal receipt in terms of performance and reliability. The authors introduce several techniques for reliably applying GPS synchronization to power system protection, control and monitoring especially in the event of GPS signal loss or failure. A T-RAIM, (time receiver autonomous integrity monitoring) function has been tested and the ability to maintain synchronizing signal stability was observed when a satellite anomaly occurred in January 2004. The actual service experience of a GPS based line current differential relay developed by the authors and now in commercial operation in Europe are described in this paper

Technology and Experience of Fully Numerical Differential Protection Communicating over Metallic Pilot-Wire

Pilot-wire differential relays have a long track-record of providing effective and reliable protection for overhead lines and underground cables in many parts of the world. The conventional analogue or electromechanical types are, however, limited in that they cannot provide the high performance and advanced features which have become commonplace in modern digital protection systems. The authors have developed a numerical, phase-segregated, current differential relay that applies digital communication techniques over conventional metallic pilot communication circuits, thus allowing utilities to re-use their existing copper links while benefiting from the advantages of numerical relay technology. This paper describes how the problems of limited bandwidth and interference which are imposed by the use of metallic circuits have been overcome, and how a high degree of immunity to communication failures has been achieved. Also his paper describes the result of a field test at a power utility in Asia