ABB Relion 670 series - Stub protection STBPTOC (50 STB); Introduction; Principle of operation

Function Range or value Accuracy
Reset ratio, residual
current
> 95% -
Phase current pickup for
blocking of contact
function
(5-200)% of lBase ± 1.0% of I
n
at I £ I
n
± 1.0% of I at I > I
n
Reset ratio > 95% -
Timers (0.000-60.000) s ± 0.5% ±10 ms
Operate time for current
detection
10 ms typically -
Reset time for current
detection
15 ms maximum -
7.9 Stub protection STBPTOC (50STB)
Function description IEC 61850
identification
IEC 60617
identification
ANSI/IEEE C37.2
device number
Stub protection STBPTOC
3I>STUB
SYMBOL-T V1 EN
50STB
7.9.1 Introduction
When a power line is taken out of service for maintenance and the line disconnector is
opened in multi-breaker arrangements the voltage transformers will mostly be outside
on the disconnected part. The primary 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
transformers and the open disconnector. The three-phase instantaneous overcurrent
function is released from a normally open, 89b auxiliary contact on the line disconnector.
7.9.2 Principle of operation
The sampled analog phase currents are pre-processed in a discrete Fourier filter (DFT)
block. From the fundamental frequency components of each phase current the RMS
value of each phase current is derived. These phase current values are fed to a
comparator in the stub protection function STBPTOC (50STB). In a comparator the
RMS values are compared to the set operating current value of the function IPickup.
Section 7 1MRK505222-UUS C
Current protection
462
Technical reference manual