59Vx Overvoltage Protection - Vx; Overview Of Function; Structure Of The Function - Siemens Reyrolle 7SR5 Manual

5.18 59Vx Overvoltage Protection – Vx

Overview of Function

5.18.1
Single phase overvoltage protection is used to:
•
Monitor the primary system voltage and provide alarms for values outside of normal limits by monitoring
the single phase voltage inputs
•
Protect equipment (for example, plant components, machines, etc.) against insulation failure due to
overvoltage
•
Decouple or reconfigure changeover systems due to overvoltage (for example, wind power supply or
parallel sources)
Overvoltages are typically caused by loss of connection to load or sudden reduction in load, voltage controller
failure at the transformer and error during control operations.
Abnormally high voltages in power systems are typically caused by:
•
Transformer or generator voltage controller malfunction or
•
Incorrect switching or control operations on long lines under low-load conditions or
•
Following load shedding or
•
Islanded operation or disconnected generators
Overvoltages can be caused by resonances between capacitor banks and line or transformer inductances.
5.18.2

Structure of the Function

The single phase undervoltage 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 A59PTOV* in IEC 61850.
The function monitors the primary system using the single phase VT input e.g. VT4. The fundamental
frequency component is measured from processing of the measured voltage samples.
•
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.
Reyrolle 7SR5, Transformer Protection Device, Device Manual
C53000-G7040-C015-1, Edition 11.2019
Protection and Automation Functions
5.18 59Vx Overvoltage Protection – Vx
271