Undervoltage Protection with Positive-Sequence Voltage
Overview of Functions
The Undervoltage protection with positive-sequence voltage function (ANSI 27):
•
Monitors the permissible voltage range
•
Protects equipment (for example, plant components and machines) from damages caused by under-
voltage
•
Protects motors and generators from inadmissible operating states and a possible loss of stability in the
event of voltage dips
2-phase short circuits or ground faults lead to an unbalanced voltage collapse. In comparison to three 1-phase
measuring systems, such events have no noticeable impact on the positive-sequence voltage. This makes this
function particularly suitable for the assessment of stability problems.
Structure of the Function
The Undervoltage protection with positive-sequence voltage function is used in protection function
groups, which are based on voltage measurement.
The Undervoltage protection with positive-sequence voltage function comes factory-set with 2 tripping
stages. A maximum of 3 tripping stages can be operated simultaneously in the function. The tripping stages
have an identical structure.
The protection function is structured such that one current-flow criterion can act on all undervoltage protec-
tion stages (see Figure 6-205). If the protection function group used has no current measurement, you can
only set the current-flow criterion as fulfilled via the corresponding binary input signal.
[dwstuvu1-110211-01.tif, 3, en_US]
Figure 6-205 Structure/Embedding of the Function
6.30
6.30.1
6.30.2
Protection and Automation Functions
6.30 Undervoltage Protection with Positive-Sequence Voltage
750 SIPROTEC 5, Overcurrent Protection, Manual
C53000-G5040-C017-8, Edition 07.2017
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