Broken Wire Monitoring Of Voltage Transformer Circuits - Siemens SIPROTEC 7SK80 Manual

Functions
2.10 Monitoring Functions

2.10.1.6 Broken Wire Monitoring of Voltage Transformer Circuits

Requirements
This function is only available in device version „World" (Ordering Information Pos. 10 = B) since it is only used
in certain regions. Furthermore, the measurement of all three phase-to-ground voltages (Van, Vbn, Vcn) is
a requirement. If only two phase-to-phase voltages were measured, it would not be possible to evaluate two of
the required criteria.
Task
The broken wire function monitors the voltage transformer circuits of the secondary system with regard to fail-
ure. A distinction is made between single-pole, two-pole and three-pole failures.
Mode of Operation / Logic
The values required for the respective criteria are calculated from the calculated displacement voltage and the
measured three phase currents and a decision is made. The resulting alarm message may be delayed. A block-
ing of the protection functions is however not effected. This is done by the measuring voltage failure detection.
The broken wire monitoring is also active during a fault. The function may be enabled or disabled.
The following logic diagram shows how the broken wire monitoring functions.
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SIPROTEC, 7SK80, Manual
E50417-G1140-C344-A4, Release date 08.2010