Overvoltage Protection with Negative-Sequence Voltage/Positive-
Sequence Voltage
Overview of Functions
The function Overvoltage protection with negative-sequence voltage/positive-sequence voltage is used
to:
•
Monitor the power system and electric machines for voltage unbalances
•
Establish a release criterion of overcurrent protection for unbalanced faults
Voltage unbalances can be caused by various factors:
•
The most common cause is unbalanced load, caused by different consumers in the individual phases, for
example.
•
Voltage unbalance can also be caused by phase failure, for example due to a tripped 1-phase fuse, a
broken conductor, etc.
•
Other causes can include faults in the primary system, for example, at the transformer or in installations
for reactive-power compensation.
Structure of the Function
The Overvoltage protection with negative-sequence voltage/positive-sequence voltage function is used
in protection function groups, which are based on voltage measurement.
The Overvoltage protection with negative-sequence voltage/positive-sequence voltage function comes
factory-set with 2 stages. A maximum of 3 stages can be operated simultaneously in the function. The stages
have an identical structure.
[Structure-V2/V1_20150521, 2, en_US]
Figure 6-194 Structure/Embedding of the Function
General Functionality
Description
Logic
The following figure represents the logic of the average-value calculation of the ratio of negative-sequence
voltage to positive-sequence voltage. The average value is forwarded to all subordinate stages.
6.28
6.28.1
6.28.2
6.28.3
6.28.3.1
Protection and Automation Functions
6.28 Overvoltage Protection with Negative-Sequence Voltage/Positive-Sequence Voltage
SIPROTEC 5, Overcurrent Protection, Manual 727
C53000-G5040-C017-8, Edition 07.2017
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