ABB Relion 670 Series Technical Reference Manual page 468

Section 7
Current protection
7.9
7.9.1
7.9.2
462
Function
Reset ratio, residual
current
Phase current pickup for
blocking of contact
function
Reset ratio
Timers
Operate time for current
detection
Reset time for current
detection
Stub protection STBPTOC (50STB)
Function description
Stub protection
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.
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.
Range or value
> 95%
(5-200)% of lBase
> 95%
(0.000-60.000) s
10 ms typically
15 ms maximum
IEC 61850
identification
STBPTOC
1MRK505222-UUS C
Accuracy
-
± 1.0% of I at I £ I
n n
± 1.0% of I at I > I
n
-
± 0.5% ±10 ms
-
-
IEC 60617 ANSI/IEEE C37.2
identification device number
50STB
3I>STUB
SYMBOL-T V1 EN
Technical reference manual