ABB RELION REB500 Technical Manual page 177

1MRK 505 406-UEN B
I
I Start
I B
IEC19000469 V1 EN-US
Figure 65: Tripping characteristic of Inverse time earth fault overcurrent protection
c-Setting can also be set to RXIDG , in which case the functions inverse characteristic
The
corresponds to that of the relay Type RXIDG:
t s [ ] 5.8 1.35
The parameter
Multiplier k1-Setting
The multiplier
shifted. This is used for grading a series of relays along a line to achieve discrimination.
For example, in the case of the very inverse characteristic, the constant c = 1 and the factor k
13.5. The operating time t is given by the equation:

t
Assuming a grading time of 0.5 s at 6 times the base current I
each of the relays is given by:
k = 5 t
1
For operating times between 0.5 and 2.5 s, this results in the following settings for k
Bay protection functions REB500
Technical manual
t min
 
Ln I I ( )
B
k1-Setting has no influence in this case.
k1-Setting enables the earth fault overcurrent inverse time characteristic to be
k
1
3 I

0
1
I
B
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k1
t =
c
I
1
I B
180000064-IEC19000469-1-en.vsdx
Bay protection functions
t
is required, the factor k
B
Section 5
≤
1
for
1
:
1
171