Siemens SIPROTEC 5, Manual

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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. In addition to jeopardizing the secondary circuit by high voltages,
such interruptions can mimic the presence of differential currents for the differential protection, as caused by
short circuits in the protected object. To prevent overfunctions due to faulty current values, you can program
the affected protection functions to be blocked.
Structure of the Function
The Broken-wire detection function is structurally anchored in the power-system data as well and in various
protection function groups.
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Figure 8-13 Structure/Embedding of the Function
The Broken-wire detection function consists of several stages.
1. Broken wire suspected (power-system data)
•
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.
2. Broken-wire check (Protection function group)
•
Current phases suspected to have a broken wire are tested for plausibility using exclusion criteria.
•
A valid exclusion criterion resets the broken-wire suspicion and cancels any existing blocking of protec-
tion functions.
8.3.5
8.3.5.1
8.3.5.2
Supervision Functions
8.3 Supervision of the Secondary System
380 SIPROTEC 5, Fault Recorder, Manual
C53000-G5040-C018-5, Edition 11.2017