ABB RELION REX640 Technical Manual page 603

1MRS759142 F
When
protection operate time as a function of estimated effective earth-fault current
(taking into account the effect of settings
is according to equation below:
In IFPTOC function, the preferred presentation of operation timer characteristics
is by plotting the protection operate time as a function of permissible/estimated
earth-fault current as illustrated in figures from
345
Consider next three examples with
Table 628: Comparison of operation times given in EN50522 with IFPTOC. The
theoretical operate time of IFPTOC has been calculated assuming CB delay Comp =
0 s
EN50522, U
716
654
537
220
117
96
86
85
Example 2a. Inverse time operation of IFPTOC, when
current based" and
Figure 343
in
A). IFPTOC is set to have minimum operate time 100 ms and maximum operate
time of 5000 ms. Setting
10 ohms. Reduction factor = 1.0. For illustrating the operating speed requirement
of protection, limits of touch voltage durations defined in standard EN50522
scaled the into corresponding earth-fault current requirements using the maximum
earthing resistance R
feeder are shown for reference.
REX640
Technical Manual
EF current Str Val is 0.5%*400 A = 2 A. The lower setting EF
for setting
current Str Val is used, the higher sensitivity in terms of fault resistance
can be obtained. Sensitivity in terms of fault resistance depends also
on the network parameters (nominal voltage, damping and detuning) as
Equation 120
described by
Operating curve type = "Inverse time EN50522" is selected, then the
.
[V]
tp
Operating curve type = "Inverse time EN50522" is illustrated
. Start value for operation is set to be 0.02*In (2 A if primary 100
Emax
.
Reduction factor and Enable harmonics )
Operating curve type = "Inverse time EN50522":
EN50522, t [sec]
f
0.05
0.1
0.2
0.5
1
2
5
10
UTp multiplier is 1.0 and setting Maximum earthing Ris is
Maximum earthing Ris ) encountered in protected
(setting
Protection functions
Figure 343 Figure 344
,
IFPTOC, t Theoretical [sec]
f
0.04
0.12
0.20
0.50
1.00
1.59
5.02
8.48
Operation principle = "EF-
(Equation 121)
Figure
and
603