ABB RELION REX640 Technical Manual page 615

1MRS759142 F
1.
2.
3.
4.
5.
REX640
Technical Manual
Reduction factor and Maximum earthing Ris are used to scale the
Settings
estimated effective earth-fault current value into corresponding touch voltage
or earth-potential rise estimate.
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 632: Permissible touch voltages U
as a function of the fault duration t
multiplier as a parameter
Fault duration t Permissible touch
f
[sec.] voltage, U
multiplier = 1.0 [V]
0.05 716
0.10 654
0.20 537
0.50 220
1.00 117
2.00 96
5.00 86
10.00 85
Minimum touch voltage or earth potential rise magnitude (considering the
Reduction factor ), which must be exceeded for the function to start, is
effect of
Touch Vol Str Val . It is important to set setting Touch Vol
defined with setting
Str Val 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 = "Touch
voltage based" and
selected. Setting
effective earth-fault current value to corresponding touch voltage or
earth potential rise value.
Reduction factor considers the fact that only part of the earth-
Setting
fault current (I
F
earthing and touch voltages.
Minimum practical value for setting
CT primary current multiplied by setting
example, in case CT primary current is 200 A, and
Ris = 10 ohm, then minimum practical value for setting Touch Vol Str
Val is 0.5%*200 A*10 ohm = 10 V. For CT with 400 A primary current,
then minimum practical value for setting
A*10 ohm = 20 V. The lower setting
higher sensitivity in terms of fault resistance can be obtained. Sensitivity
UTp multiplier , see table below.
and earth potential rise U
Tp
according to standard EN50522 with U
f
Permissible earth
, U potential rise, U
Tp Tp
U
Tp
[V]
1432
1308
1074
440
234
192
172
170
Operating curve type = "Inverse time EN50522" is
Maximum earthing Ris is needed to scale the estimated
) will flow back through "remote" earth and introduces
Touch Vol Str Val is 0.5% of
Touch Vol Str Val is used, the
Protection functions
Permissible earth
, potential rise, U
E
multiplier = 2.0 U multiplier = 4.0
Tp
[V]
2864
2616
2148
880
468
384
344
340
Maximum
Maximum earthing Ris . For
Maximum earthing
Touch Vol Str Val is 0.5%*400
values
E
Tp
,
E
615