Siemens Siprotec 7VK61 Manual page 70

Functions
2.3 Overcurrent protection (optional)
End fault protection
A further overcurrent stage is the stub protection. It can however also be used as a normal additional definite
time overcurrent stage, as it functions independent of the other stages.
A stub fault is a short-circuit located between the current transformer set and the line isolator. It is of particular
importance with the 1
Figure 2-14
If a short circuit current I
range between the current transformers I
that carry the short-circuit current can be tripped without delay. The two sets of current transformers are con-
nected in parallel such that the current sum I
The stub protection is an overcurrent protection which is only in service when the state of the line isolator indi-
cates the open condition via a binary input „>I-STUB ENABLE". The binary input must therefore be operated
via an auxiliary contact of the isolator. In the case of a closed line isolator, the stub protection is out of service.
For more information see the next logic diagram.
If the stub protection stage is to be used as a normal definite time overcurrent stage, the binary input „>BLOCK
I-STUB", should be left without allocation or routing (matrix). The enable input „>I-STUB ENABLE", however,
has to be constantly activated (either via a binary input or via integrated logic (CFC) functions which can be
configured by the user.
70
1
/ circuit breaker arrangements.
2
1
Stub fault at an 1 / circuit breaker arrangement
2
and/or I flows while the line isolator 1 is open, this implies that a fault in the stub
A B
A
, I , and the line isolator exists. The circuit breakers CBA and CBC
B
+ I represents the current flowing towards the line isolator.
A B
C53000-G1176-C159-3, Release date 05.2009
SIPROTEC, 7VK61, Manual