Time-Delayed Overcurrent Protection (51); Time-Delayed Overcurrent Protection - Siemens Reyrolle 7SR45 Argus Device Manual

Functions

3.3 Time-Delayed Overcurrent Protection (51)

3.3

Time-Delayed Overcurrent Protection (51)

Overview of the Function (51)
Time-delayed overcurrent protection is used to provide:
•
Short-circuit detection in electric equipment
•
Coordinated operation with other devices using current and time-graded settings
Structure of the Function (51)
The time-delayed overcurrent protection function element has group-dependent settings. These settings can
be different in each settings group – group numbers (Gn) 1 and 2.
The function monitors the primary system current using the 3-phase current transformer inputs, for example
CT1/2/3.
The basic time-delayed overcurrent protection function (51) is characterized by the following:
•
Current measurement is based on the fundamental current.
•
A number of time versus current operate curves are selectable based on IEC and ANSI standards.
•
LED operations are provided for each phase. A general pickup and 51‑n output are also provided.
44 Reyrolle, 7SR45, Device Manual
C53000-G7040-C101-2, Edition 09.2020