ABB REG670 Technical Manual page 1258

Section 25
Inverse time characteristics
1252
æ ö
ç ÷
t
[ ]
ç ÷
= ×
t s r k
ç ÷
2
æ ö
i
ç ç ÷ - ÷
1
è è ø ø
>
in
EQUATION1197 V2 EN
where:
The set value t is the reset time in case of zero current after fault clearance.
r
The possibility of choice of reset characteristics is to some extent dependent of the
choice of time delay characteristic.
For the definite time delay characteristics the possible reset time settings are
instantaneous and IEC constant time reset.
For ANSI inverse time delay characteristics all three types of reset time characteristics
are available; instantaneous, IEC constant time reset and ANSI current dependent
reset time.
For IEC inverse time delay characteristics the possible delay time settings are
instantaneous and IEC set constant time reset).
For the programmable inverse time delay characteristics all three types of reset time
characteristics are available; instantaneous, IEC constant time reset and ANSI current
dependent reset time. If the current dependent type is used settings pr, tr and cr must
be given, see equation 166:
æ ö
ç ÷
t
[ ]
ç ÷
=
t s r
ç pr ÷
æ ö
i
ç ÷
ç ÷ -
cr
è è ø ø
>
in
EQUATION1198 V2 EN
For RI and RD inverse time delay characteristics the possible delay time settings are
instantaneous and IEC constant time reset.
When inverse time overcurrent characteristic is selected, the operate
time of the stage will be the sum of the inverse time delay and the set
definite time delay. Thus, if only the inverse time delay is required, it
is of utmost importance to set the definite time delay for that stage to
zero.
×
k
1MRK502052-UEN B
(Equation 165)
(Equation 166)
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