Negative-Sequence Protection
Overview of Functions
The function Negative-sequence protection (ANSI 46):
•
Detects 1-phase or 2-phase short circuits in the electrical power system with clearly increased sensitivity
compared to the classical overcurrent protection
•
Protects electric machines during excessive unbalanced load
•
Reports unbalanced load conditions in the electricity supply system
•
Detects phase interruptions in the primary system
•
Locates short circuits or inversions in the connections to the current transformers
Structure of the Function
The Negative-sequence protection function is used in protection function groups with current measure-
ment.
The function is preconfigured by the manufacturer with 2 Definite-time negative-sequence protection
stages.
In the function Negative-sequence protection, the following stages can be operated simultaneously:
•
3 stages Definite-time negative-sequence protection
•
2 stages Inverse-time negative-sequence protection
The stages have an identical structure. Stages that are not preconfigured are shown in gray in the following
figure.
[dwnspstr-271112-01.tif, 3, en_US]
Figure 7-183 Structure/Embedding of the Function
If the device is equipped with the Inrush-current detection function, the stages can be stabilized against
operate due to transformer-inrush currents.
7.25
7.25.1
7.25.2
Protection and Automation Functions
7.25 Negative-Sequence Protection
SIPROTEC 5, High-Voltage Bay Controller, Manual 871
C53000-G5040-C015-9, Edition 11.2017
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