Function Range or value AccuracyReset ratio > 95% -Timers (0.000-60.000) s ± 0.5% ±10 msOperate time for currentdetection20 ms typically -Reset time for currentdetection10 ms maximum -6.8 Stub protection STBPTOC (50STB)6.8.1 IdentificationFunction description IEC 61850identificationIEC 60617identificationANSI/IEEE C37.2device numberStub protection STBPTOC3I>STUBSYMBOL-T V1 EN50STB6.8.2 FunctionalityWhen a power line is taken out of service for maintenance and the line disconnector isopened, line side voltage transformers will be on the disconnected part of the line. Theprimary line distance protection will thus not be able to operate and must be blocked.The stub protection STBPTOC (50STB) covers the zone between the current transformersand the open disconnector. The three-phase instantaneous overcurrent function is releasedfrom a normally open, 89b auxiliary contact on the line disconnector.6.8.3 Function blockANSI08000051-1-en.vsdSTBPTOC (50STB)I3P*BLOCKENABLETRIPPICKUPANSI08000051 V1 ENFigure 57: STBPTOC (50STB) function blockSection 6 1MRK 511 287-UUS ACurrent protection142Technical manual
