47 Sequence Overvoltage Protection; Overview Of Function; Structure Of The Function - Siemens 7SR51 Device Manual

5.9

47 Sequence Overvoltage Protection

Overview of Function

5.9.1
Sequence overvoltage protection is used to:
•
Monitor symmetrical positive sequence voltage content which is not affected by unbalance in the 3
phase voltages
•
Monitor unbalance voltage and provide tripping or alarms for values outside of normal limits
•
Protect equipment (for example, plant components, machines, etc.) against damages caused by unbal-
ance
•
Detect overvoltage, system faults, fuse failure, and broken conductors

Structure of the Function

5.9.2
The Sequence Overvoltage Protection function has group dependent settings. These settings can be different
in each settings group – group numbers (Gn) 1 to 4.
This function corresponds to the logical node A47PTOV* in IEC 61850.
The function monitors the primary system using the 3 phase VT inputs e.g. VT1, VT2 and VT3. The funda-
mental frequency component is measured from processing of the measured voltage samples. Operation can
be based on the user selection of the positive phase sequence voltage, negative phase sequence voltage or
zero phase sequence voltage.
NOTE
i i
Where VT1/2/3 configuration is selected to Va,Vb,Vc then zero phase sequence overvoltage cannot be
measured.
A definite time delayed operate characteristic is used. Settings are provided for operate (pickup) threshold
voltage, reset voltage level (hysteresis/drop‑off) and time delay.
Outputs are provided for pickup and operation.
Correct operation is dependent on valid information being received from the VT inputs, incorrect measure-
ment and operation may result if a VT fuse fails. When a fuse failure is detected, 60VTS function, the 47 func-
tion can be inhibited.
When a function inhibit is applied from a binary input, logic signal, VTS, or undervoltage guard, an element
that is picked up will be reset. Reset of the inhibit will allow restart of the operating delay.
Reyrolle 7SR5, Overcurrent Protection Device, Device Manual
C53000-G7040-C014-1, Edition 11.2019
Protection and Automation Functions
5.9 47 Sequence Overvoltage Protection
195