ABB Relion 670 Series Applications Manual page 239

1MRK 511 358-UUS A
TD
=
t
op
æ
ç
x I
è
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
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 TD
op
EQUATION1742-ANSI V1 EN-US
where:
t op
TD
M
A, B, C and P are user settable coefficients which determine the curve used for Inverse Time Overcurrent TOC/
When the equation
the OC1 it is obvious that if the following rules are followed:
1. set TD 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
4.
set
5. set
6. set
Application manual
1
×
2
x
2
ö
I
NS
÷
×
ø
r
CurrentInput to value NegSeq
CurveType_OC1 to value Programmable
æ A ö
+
×
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
IDMT calculation
100 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
PickupCurr_OC1 equal to the value x
TD_OC1 = 20
A_OC1 = 1/0.07 2
= 204.0816
B_OC1 = 0.0, C_OC1 = 0.0 and P_OC1 = 2.0
PickupCurr_OC1 = 7%
102 for the inverse time characteristic of
Section 10
Multipurpose protection
(Equation 102)
(Equation 103)
233