ABB REB670 Series, Applications Manual

Page: 240 / 476

2
2
2
1
1
op
m
r
k
x
t
I
x I x
×
=
æ ö
-
ç ÷
×
è ø
EQUATION1378 V1 EN-US
(Equation 82)
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 PosSeq
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
op
P
A
t k B
M C
æ ö
= × +
ç ÷
-
è ø
EQUATION1375 V1 EN-US
(Equation 83)
where:
t
op
is the operating time in seconds of the Inverse Time Overcurrent TOC/IDMT algorithm
k is time multiplier (parameter setting)
M is ratio between measured current magnitude and set pickup current level
A, B, C and P are user settable coefficients which determine the curve used for Inverse Time Overcurrent
TOC/IDMT calculation
When the equation 82 is compared with the equation 83 for the inverse time characteristic of
the OC1 step in it is obvious that if the following rules are followed:
1. set k equal to the IEC or ANSI standard generator capability value
2. set parameter
A_OC1 equal to the value 1/x2
3. set parameter
C_OC1 equal to the value 1/x2
4. set parameters
B_OC1 = 0.0 and P_OC1=2.0
5. set StartCurr_OC1 equal to the value x
then the OC1 step of the CVGAPC function can be used for generator negative sequence
inverse overcurrent protection.
1. select positive sequence current as measuring quantity for this CVGAPC function
2. make sure that the base current value for CVGAPC function is equal to the generator rated
current
3. set k = 37.5 for the IEC standard or k = 41.4 for the ANSI standard
4. set
A_OC1= 1/1.162 = 0.7432
5. set
C_OC1= 1/1.162 = 0.7432
6. set
B_OC1 = 0.0 and P_OC1 = 2.0
7. set
StartCurr_OC1 = 116%
Proper timing of CVGAPC function made in this way can easily be verified by secondary
injection. All other settings can be left at the default values. If required delayed time reset for
OC1 step can be set in order to insure proper function operation in case of repetitive overload
conditions.
Section 10 1MRK 505 370-UEN D
Multipurpose protection
234 Busbar protection REB670
Application manual