ABB REC670 Applications Manual page 284

Section 11
Multipurpose protection
278
TD
=
t
op
2
æ ö
I
NS
ç ÷
I
è ø
r
EQUATION1740-ANSI V1 EN-US
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-US
Equation 96 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-US
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 511 401-UUS A
(Equation 96)
(Equation 97)
(Equation 98)
Bay control REC670 2.2 ANSI
Application manual