ABB REG670 - Page 460

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
op
P
A
t k B
M C
æ ö
= × +
ç ÷
-
è ø
EQUATION1375 V1 EN (Equation 252)
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 249 is compared with the equation 251 for the inverse time
characteristic of 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 A_OC1 equal to the value 1/x2
3. set B_OC1 = 0.0, C_OC1=0.0 and P_OC1=2.0
4. 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.
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 k_OC1 = 20
4.
set A_OC1= 1/0.07
2
= 204.0816
5. set B_OC1 = 0.0, C_OC1 = 0.0 and P_OC1 = 2.0
6. set StartCurr_OC1 = 7%
Proper timing of the 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 ensure proper function operation
in case of repetitive unbalance conditions.
Section 12 1MRK 502 071-UEN -
Multipurpose protection
454 Generator protection REG670 2.2 IEC and Injection equipment REX060, REX061, REX062
Application manual