ABB 650 series Applications Manual page 90

Section 6
Multipurpose protection
84
By defining parameter x equal to the per unit value for the desired pickup for the
overload IED in accordance with the following formula:
x = 116% = 1.16 pu
EQUATION1377 V2 EN-US
formula 3.5can be re-written in the following way without changing the value for
the operate time of the generator stator overload IED:
1
×
k
2
x
=
t
op
2
æ ö
I 1
-
m
ç ÷
×
2
x I x
è ø
r
EQUATION1378 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 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-US
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 17 is compared with the equation
characteristic of the OC1 step in it is obvious that if the following rules are
followed:
1MRK 511 423-UEN A
(Equation 16)
(Equation 17)
(Equation 18)
18 for the inverse time
Bay control REC650 2.2 IEC
Application manual