ABB REB670 Applications Manual page 270

Section 10
Multipurpose protection
264
TD
=
t
op
2
æ ö
I
NS
ç ÷
I
è ø
r
EQUATION1740-ANSI V1 EN
where:
t is the operating time in seconds of the negative sequence overcurrent IED
op
TD is the generator capability constant in seconds
I is the measured negative sequence current
NS
I is the generator rated current
r
By defining parameter x equal to maximum continuous negative sequence rating of the
generator in accordance with the following formula
= =
x 7% 0.07 pu
EQUATION1756-ANSI V1 EN
Equation 80 can be re-written in the following way without changing the value for the
operate time of the negative sequence inverse overcurrent IED:
1
×
TD
2
x
=
t
op
2
æ ö
I
NS
ç ÷
×
è x I ø
r
EQUATION1741-ANSI V1 EN
In order to achieve such protection functionality with one CVGAPC functions the
following must be done:
1. Connect three-phase generator currents to one CVGAPC instance (for example,
GF01)
2. Set parameter CurrentInput to value NegSeq
3. Set base current value to the rated generator current in primary amperes
4. Enable one overcurrent step (for example, OC1)
5. Select parameter CurveType_OC1 to value Programmable
1MRK 505 337-UUS -
(Equation 80)
(Equation 81)
(Equation 82)
Application manual