L2275
Emax UL
68/132
Doc. N°
Mod.
RH0109002
Apparatus
Scale
Page N°
Relay 2
Relay 1
Relay 3
DB1in
DF3in
DF1out
DB3out
DF3out
DB3in
DF2in
DB2out
DF2out
DF1in
DB1out
DB2in
Dir
.
F
o
rw
ard 1
Dir
.
Bac
k
w
a
rd 1
Load A
Load B
Generator
Fault
Operation, with zone selectivity disabled, is the following:
!
If Imax > I7 and current direction determined
≠
direction set
"
no alarm;
!
If Imax > I7 and current direction determined = direction set
"
times and opens;
!
If Imax > I7 and current direction cannot be determined
"
times and opens considering as the direction the one selected with the “Direction”
parameter.
N.B.:
•
Protection D always considers I neutral (Neutral sel.) = 100%.
•
Protection D is not available with 250 and 400 A CT.
•
See Warnings par. 15.3.2.
15.2.6.3.1 Start-up threshold “D”
The function is disabled by selecting [-----] at the “StartUp” parameter on the protection “D” page.
The behavior of the function is identical to the one described for protection “S” (see par. 15.2.6.2.2).
15.2.6.3.2 Zone selectivity “D”
Zone selectivity “D” can only be set [On] in the case where zone selectivity “S” and “G” are set on [Off] and there is an auxiliary power supply.
It uses 4 signals, two outputs two inputs:
#
DFin (K51/DFin), DFout (K51/DFout) for signaling in the case of “forward” direction of the fault current;
#
DBin (K51/DBin), DBout (K51/DBout) for the signaling in the case of “backward” direction of the fault current.
With zone selectivity activated, if the direction is not determined, the protection trips considering the shorter time programmed of forward and
backward and without activating any output (DFout or DBout).
Setting the “Direction” parameter for operation with zone selectivity has no influence.
The typical configuration of the power circuit breaker system for which the use of zone selectivity “D” is foreseen is the ring one, as shown as
an example in the following figure.
In the case when a fault is determined on one of the sections of the system (Load A), the end power circuit breakers of the section itself (Relay1
and Relay2) communicate the presence of the fault to the power circuit breakers connected (Relay3) setting the DFout or DBout output signals
on the basis of the direction of the current (DFout1=On, DB2out=On). In particular, the power circuit breakers which limit the section of the fault
see the direction of the fault current in different ways (Relay 1 “forward” and Relay 2 “backward”).
The power circuit breakers which limit the section involved by the fault intervene with selectivity time ts (130...500 ms) whereas the power circuit
breakers connected time with time t7 (Relay3). In this way the system is isolated by excluding the fault area.
15.2.6.4
Protection “I”
The protection, which can be disabled, is made with intentional delay nil.
In the case where zone selectivity “S” (or “D”) is active, during the trip of the relay for “I”, the ZSO (or DFW and BFW) output signal is activated
in any case to guarantee correct operation of the supply side (and load side) relay.
15.2.6.4.1 Start-up threshold “I”
The start-up function can be selected.
The function is disabled by selecting ‘-----’ at the “StartUp” parameter on the protection “I” page.
The behavior of the function is identical to the one described for protection “S” (see par. 15.2.6.2.2).
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