ABB REJ 513, Руководство пользователя

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REJ 513 User’s Guide
ABB Substation Automation
Products and Systems
1MRS750613-MUM
20
RI-type characteristic
The RI-type characteristic is a special characteristic that is principally used for
obtaining time grading with mechanical relays. The characteristic can be expressed
mathematically:
t [s] =
k
I
I
0 339 0 236 . .
− × >
where t = operate time in seconds
k = time multiplier
I = phase current
I> = set start current.
The RI-type characteristic is illustrated in figure 2.1.3.3-5.
RD-type characteristic
The RD-type characteristic is a special characteristic that is principally used in earth-
fault protection which requires a high degree of selectivity even at high resistance
faults. In this case the protection can operate in a selective way even if it is not
directional. Mathematically, the time/current characteristic can be expressed as
follows:
t [s] = 5.8-1.35 x log
e
I
k I
× >




where t = operate time in seconds
k = time multiplier
I = phase current
I> = set start current.
The RD-type characteristic is illustrated in figure 2.1.3.3-6.