46 Negative-Sequence Overcurrent Protection
Overview of Functions
Negative sequence overcurrent protection is used to:
•
Detect 1-phase or 2-phase short circuits in the electrical power system
•
Protect electric machines during excessive unbalanced load
•
Alarm for unbalanced system load conditions
Structure of the Function
The negative phase sequence overcurrent protection 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 A46DTPTOC* and A46ITPTOC* in IEC 61850.
The function monitors the primary system using the 3 phase current inputs e.g. CT1/2/3. The negative
sequence phase (NPS) component of current (I
2
) is derived from the 3 phase currents.
The function has 2 element types:
•
Definite-time negative-sequence protection (46DT)
•
Inverse-time negative-sequence protection (46IT)
Blocking of the Stage
When a binary input configured as Inhibit 46DT-n or Inhibit 46IT-n is operated, the associated func-
tion element will reset.
5.7
5.7.1
5.7.2
Protection and Automation Functions
5.7 46 Negative-Sequence Overcurrent Protection
180 Reyrolle 7SR5, Transformer Protection Device, Device Manual
C53000-G7040-C015-1, Edition 11.2019
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