ABB REB670 Series Applications Manual page 238

Section 10
Multipurpose protection
=
x 7%
EQUATION1373 V1 EN-US
Equation
time of the negative sequence inverse overcurrent IED:
=
t
op
æ
ç
è
EQUATION1374 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
3. Set base current value to the rated generator current in primary amperes
4. Enable one overcurrent step (for example, OC1)
5. Select parameter
= ×
t k
op
EQUATION1375 V1 EN-US
where:
op
t
k
M
A, B, C and P are user settable coefficients which determine the curve used for Inverse Time Overcurrent
When the equation
the OC1 it is obvious that if the following rules are followed:
1. set k equal to the generator negative sequence capability value
2. set
3. set
4. set
then the OC1 step of the CVGAPC function can be used for generator negative sequence
inverse overcurrent protection.
For this particular example the following settings shall be entered to insure proper function
operation:
1. select negative sequence current as measuring quantity for this CVGAPC function
2. make sure that the base current value for the CVGAPC function is equal to the generator
rated current
3. set
232
=
0, 07 pu
76 can be re-written in the following way without changing the value for the operate
1
×
k
2
x
2
ö
I
NS
÷
×
x I
ø
r
CurrentInput to value NegSeq
CurveType_OC1 to value Programmable
æ ö
A
+
B
ç ÷
P -
è M C ø
is the operating time in seconds of the Inverse Time Overcurrent TOC/IDMT algorithm
is time multiplier (parameter setting)
is ratio between measured current magnitude and set pickup current level
TOC/IDMT calculation
76 is compared with the equation
A_OC1 equal to the value 1/x2
B_OC1 = 0.0, C_OC1 =0.0 and P_OC1 =2.0
StartCurr_OC1 equal to the value x
k_OC1 = 20
78 for the inverse time characteristic of
Busbar protection REB670
1MRK 505 370-UEN D
(Equation 77)
(Equation 78)
(Equation 79)
Application manual