Siemens 7SJ85 - Broken-Wire Detection; Overview of Functions; Structure of the Function; Function Description

No. Information Data Class
(Type)
Type
_:2311:501 General:>MP-ID selection INS I
_:2311:54 General:Inactive SPS O
_:2311:52 General:Behavior ENS O
_:2311:53 General:Health ENS O
_:2311:307 General:Main-voltage failure ACD O
_:2311:308 General:Ref.-voltage failure ACD O
_:2311:309 General:Selection invalid SPS O
Broken-Wire Detection
Overview of Functions
The purpose of the broken-wire detection is to detect interruptions in the secondary circuit of the current
transformers during steady-state operation.
Structure of the Function
The Broken-wire detection function is located in the power-system data of each 3-phase current measuring
point.
[dwbwsjsk-301112-01.tif, 2, en_US]
Figure 9-23 Structure/Embedding of the Function
The tasks of Broken-wire detection are:
•
The instantaneous values of all current measuring points are checked on a phase-selective basis for
implausible values.
•
The affected phases are marked with wire-break suspected.
•
Depending on the supervision mode, you can add a marker for blocking protection functions for the
affected phases.
•
After 10 ms of broken-wire check, the wire break is reliably signaled.
Function Description
Broken Wire Suspected
The Broken-wire detection function monitors the dynamic behavior of the currents of each phase and of all
measuring points. For this purpose, the instantaneous values of the currents are checked for their plausibility.
Each expected violation must be confirmed by additional criteria before a wire break can be detected and
signaled with assurance.
The detection of the local broken wire suspected is performed on each 3-phase current measuring point of the
device selectively for each phase.
Detection:
A wire break initially manifests itself as a sudden decrease of the current below the minimum threshold of
0.06 I/I
rated.
A plausibility test on one period of past instantaneous values confirms this condition. If the criteria
for the local wire break are satisfied, the affected phase is marked with Broken wire suspected.
9.3.9
9.3.9.1
9.3.9.2
9.3.9.3
Supervision Functions
9.3 Supervision of the Secondary System
SIPROTEC 5, Overcurrent Protection, Manual 1271
C53000-G5040-C017-8, Edition 07.2017