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5.3
27Vx Undervoltage Protection – Vx
Overview of Function
5.3.1
Single phase undervoltage protection is used to:
•
Monitor the permissible voltage range and provide alarms for values outside of normal limits by moni-
toring any single phase connection point. This function is entirely independent from the 3 phase voltage
inputs.
•
Decouple or reconfigure changeover systems when loss of supply is detected.
•
To selectively disconnect loads (load shedding) to match generation capacity following a loss of genera-
tion which can be detected by undervoltage.
Undervoltages are typically caused by loss of generation, overload of lines or removal of lines from service,
voltage controller failure at the transformer and error during control operations.
5.3.2
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 A27VxPTUV* 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, Overcurrent Protection Device, Device Manual
C53000-G7040-C014-1, Edition 11.2019
Protection and Automation Functions
5.3 27Vx Undervoltage Protection – Vx
157
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