ABB RELION REX640 Technical Manual page 602

Protection functions
1.
2.
3.
4.
5.
602
Maximum earthing Ris is used to scale the touch voltage and earth
Setting
potential rise requirements defined in standard EN 50522 into corresponding
earth-fault current requirements.
UTp multiplier enables operation based on permissible earth potential
Setting
rise U , by scaling of the permissible time-touch voltage characteristics given in
E
standard EN 50522 with Setting
Table 627: Permissible touch voltages U
given in standard EN50522 converted into equivalent permissible earth-fault
current I values as a function of the fault duration t
Fp
with parameter R
Emax
ohms i.e. the maximum earthing resistance encountered in protected feeder.
Fault duration t Permissible touch
f
[sec.] voltage, U
converted into
corresponding
permissible fault
current, I
multiplier = 1.0 [A]
0.05 716 V/R
0.10 654 V/R
0.20 537 V/R
0.50 220 V/R
1.00 117 V/R
2.00 96 V/R
5.00 86 V/R
10.00 85 V/R
Minimum effective earth-fault current magnitude (considering the effect of
Reduction factor ), which must be exceeded for the function to start,
setting
is defined with setting
according to required protection sensitivity.
IDMT stage Min Op Tm setting user can define minimum allowed operate
With
time for IFPTOC i.e. this is the minimum allowed operate time of IFPTOC.
IDMT stage Max Op Tm setting user can define maximum allowed operate
With
time for IFPTOC i.e. this is the maximum allowed operate time of IFPTOC
although IDMT timer would define slower operate time.
Parameter defining maximum earthing resistance, setting
earthing Ris must be always set in case Operation principle = "EF current
Operating curve type = "Inverse time EN50522" is selected.
based" and
Maximum earthing Ris is needed to scale the touch voltage and
Setting
earth potential rise requirements defined in standard EN 50522 into
corresponding earth-fault current requirements.
Reduction factor considers the fact that only part of the earth-
Setting
fault current (I
F
earth potential rise and touch voltages.
Minimum practical value for setting
primary current. For example, in case CT primary current is 200A, then
minimum practical value for setting
1 A. For CT with 400 A primary current, then minimum practical value
UTp multiplier , see table below.
and earth potential rise U
Tp
, which is the setting
Permissible earth
potential rise,
Tp
U
E
into corresponding
permissible fault
, U current, I
Fp Tp
multiplier = 2.0 [A]
1432 V/R
Emax
1308 V/R
Emax
1074 V/R
Emax
440 V/R
Emax
234 V/R
Emax
192 V/R
Emax
172 V R
Emax
170 V/R
Emax
EF current Str Val . It is important to set this value
) will flow back through "remote" earth and introduces
EF current Str Val is 0.5% from CT
EF current Str Val is 0.5%*200 A =
. Conversion is made
f
Maximum earthing Ris in primary
Permissible earth
potential rise,
converted U converted
E
into corresponding
permissible fault
, U current, I
Fp Tp
multiplier = 4.0 [A]
2864 V/R
Emax
2616 V/R
Emax
2148 V/R
Emax
880 V/R
Emax
468 V/R
Emax
384 V/R
Emax
344 V/R
Emax
340 V/R
Emax
Technical Manual
1MRS759142 F
values
E
, U
Fp Tp
Emax
Emax
Emax
Emax
Emax
Emax
Emax
Emax
Maximum
REX640