ABB RELION REB500 Technical Manual page 60

Section 5
Bay protection functions
Underimpedance starters (UZ) up to initial pick-up
The variables at the inputs of the underimpedance starters are the phase currents I
I and the residual current I
L3
neutral voltage U
Z = -------------------
IEC19000415 V1 EN-US
Figure 14: Underimpedance starters (UZ)
Depending on the setting of the parameter
function determines initially whether one or both of the ground fault criteria are fulfilled, that
is, whether the residual current I
residual voltage U
phase-to-ground loops are measured first, otherwise just the three phase-to-phase loops.
The three phase-to-ground loops are processed as follows:
If I (or I
L1
impedances calculated as follows:
54
(3I
E
(3U ).
E 0
START
U , U , U , U ,
L1 L2 L3 E
I , I , I , I
L1 L2 L3 E
(I > 3I0 min ) AND
E
(I >0.25I max ) AND/OR
E
(U >3U0 min )
E
Y
N
(I ph > I min
Y
U Ph
Z = -----------
2 x I Ph
N
Z < Z Start
Y
Set temp.
signals "Ph",
"E"
N
All Ph-0
loops
Y
Loop =
Phase selection
U ph U ph1 – U ph2
or Z = -------------------
1x I ph + 1 x I E I ph1 – I ph2
N
Z < Z Start
Y
Log.signals =
temp.signals
END
the setting of the parameter
E
, or I ) is greater than I
L2 L3
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) and the phase-to-neutral voltages U
0
N
Gnd Fault Mode (I
exceeds the setting of the parameter
E
3U0min . Should this be the case, the three
, the corresponding loops are enabled and the loop
min
1MRK 505 406-UEN B
GUID-69036925-0AA6-488C-A93E-410F5C113C09 v1
, U , U
L1 L2 L3
(I ph1 > I min )
N
AND
(I ph2 > I min
Y
U ph1 – U ph2
Z = ---------------------
I ph1 – I ph2
Z < Z Start
J
Set temp.
signals "Ph1",
"Ph2"
All Ph-Ph
loops
Y
Selectivity
conditions
Set
log. signals
18000013-IEC19000415-1-en.vsdx
, I AND U , I OR U
0 0 0 0
3I0min and/or the
Bay protection functions REB500
, I and
L1 L2
and the
), the
0
Technical manual