ABB REG670 Applications Manual page 462

Section 12
Multipurpose protection
456
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
æ ö
A
= × +
t k B
ç ÷
op
-
P
è M C ø
EQUATION1375 V1 EN
where:
t is the operating time in seconds of the Inverse Time Overcurrent TOC/IDMT algorithm
op
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 255
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
Generator protection REG670 2.2 IEC and Injection equipment REX060, REX061, REX062
is compared with the equation
1MRK 502 071-UEN -
(Equation 256)
256 for the inverse time
Application manual