Ri-Type Characteristic - ABB REF610 Technical Reference Manual

1MRS755535
Feeder Protection Relay
Technical Reference Manual - ANSI Version

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:
TD
[ ]
=
t s
1
− ×
0 339 0 236 . .
M
t = operate time
M = multiplies of pickup current
TD = time dial
The actual operate time of the relay (see Fig. 5.1.4.9.-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 t.
The RI-type characteristic is illustrated in Fig. 5.1.4.9.-8.
REF610 REF610
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