1MRS751802-MUM
REX 521
87
Protection Relay
Technical Reference Manual, Standard Configurations
7.
Function block descriptions
The information in this chapter is adapted from the function block descriptions in
the CD-ROM
Technical Descriptions of Functions
(Section 1.5. Related documents).
See also Chapter 2. Introduction for differences between the REX 521 and the RED
500 platform in the function block descriptions of the CD-ROM.
In this chapter, the function blocks are called by their IEC names. The corresponding
ABB names for the function blocks can be found in Table 2.-1.
Note that in the CD-ROM Technical Descriptions of Functions there are more
signals presented than in this manual.
7.1.
Protection
7.1.1.
3I>, 3I>> and 3I>>>
The three-phase non-directional overcurrent function blocks are designed for non-
directional two-phase and three-phase overcurrent and short-circuit protection
whenever the DT characteristic or, as concerns 3I>, the IDMT (Inverse Definite
Minimum Time) characteristic is appropriate. Suppression of harmonics is possible.
Fig. 7.1.1.-1
Function block symbols of 3I>, 3I>> and 3I>>
3I>
BS1
BS2
GROUP
RESET
CBFP
START
TRIP
CBFP
3I>>
CBFP
BS1
BS2
GROUP
DOUBLE
RESET
BSOUT
START
TRIP
CBFP
NOC3High
3I>>>
CBFP
BS1
BS2
GROUP
DOUBLE
RESET
BSOUT
START
TRIP
CBFP
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