Field Experience with the AEP Digital Relay

This paper will briefly review the installation of the Symmetrical Component Distance Relay (SCDR) in AEP´s Matt Funk substation and discuss our field experience. Data on system performance will be presented. Special emphasis will be placed on electromagnetic susceptibility problems encountered in the field and corroborating data obtained from AEP laboratory EMI testing. Problems were encountered with the original formulation of the impedance algorithm as presented in previous papers. When dealing with the calculation of ground distance on lines with infeed, the algorithm misclassified fault types. This problem and the latest evolution of our impedance calculation formula will be discussed.