Table of Contents
Advertisement
REF 610
44
Feeder Protection Relay
Technical Reference Manual
RI-type characteristic
The RI-type characteristic is a special characteristic which is principally used for
obtaining time grading with mechanical relays. The relationship between time and
current is expressed as follows:
k
t s [ ]
=
-------------------------------------------- -
0.339 0.236
–
where
t = operate time
I = phase (or earth-fault) current value
k (or k
) = time multiplier
0
I> (or I
>) = set start value
0
Note!
The actual operate time of the relay (see Fig. 4.1.4.9.-8), includes an additional filter
and detection time, and the operate time of the trip output contact. When the operate
time of the relay is calculated as above, approximately 30 ms should be added to the
result.
The RI-type characteristic is illustrated in Fig. 4.1.4.9.-8.
I>
×
---- -
I
1MRS 755310
Advertisement
Table of Contents
