ABB RELION REX640 Technical Manual page 609

1MRS759142 F
earthing Ris in primary ohms i.e. the maximum earthing resistance encountered in
protected feeder.
Fault duration t
0.05
0.10
0.20
0.50
1.00
2.00
5.00
10.00
In some countries, safety during an earth fault is defined in terms of highest
allowed earth potential rise (EPR) as a function of fault duration. As an example,
in Finnish national Electrical Safety Regulations 89 define highest allowed earth
potential rise as a function of fault duration as shown in table below.
Table 630: Highest allowed EPR values based on Electrical Safety
Group
a
b
c
d
e1
e2
The regulations of
principle = "EF current based", setting Maximum earthing Ris is used to convert
the highest allowed earth potential risevalues into corresponding earth-fault current
values. Setting
for example for group d,
earth potential rise value to the highest allowed earth-fault current magnitude with
setting
Setting
earthing resistance encountered in protected feeder.
Table 631: Conversion of the highest allowed earth potential rise value into corre-
sponding earth-fault current values according to the Electrical Safety Regulations
REX640
Technical Manual
[sec.]
f
Highest allowed EPR [V], when earth fault is automatically
disconnected within time
t
750V/√
2000V/√
3000V/√
t
500V/√
t
750V/√
1000V/√
Table 630
are implemented into IFPTOC. In case
IEEE multiplier is set to equal the highest allowed voltage value,
IEEE multiplier = 500. Conversion of the highest allowed
Maximum earthing Ris is shown in
Maximum earthing Ris in primary ohms is selected based on the maximum
Permissible touch voltage, U
corresponding permissible fault current, I
702 V/R
Emax
496 V/R
Emax
351 V/R
Emax
222 V/R
Emax
157 V/R
Emax
111 V/R
Emax
70 V/R
Emax
50 V/R
Emax
t [sec]
t
t
t
Table 631
Protection functions
converted into
Tp
[A]
Fp
Operation
.
609