ABB Relion REC670 Applications Manual page 212

Section 10
Multipurpose protection
=
t
op
æ
ç
è
EQUATION1372 V1 EN-US
where:
t
op
k
I
NS
I
r
By defining parameter x equal to maximum continuous negative sequence rating of the
generator in accordance with the following formula
=
x 7%
EQUATION1373 V1 EN-US
Equation
time of the negative sequence inverse overcurrent IED:
=
t
op
æ
ç
è
EQUATION1374 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 k
op
EQUATION1375 V1 EN-US
where:
op
t
k
M
A, B, C and P are user settable coefficients which determine the curve used for Inverse Time Overcurrent
206
k
2
ö
I
NS
÷
I
ø
r
is the operating time in seconds of the negative sequence overcurrent IED
is the generator capability constant in seconds
is the measured negative sequence current
is the generator rated current
=
0, 07 pu
99 can be re-written in the following way without changing the value for the operate
1
×
k
2
x
2
ö
I
NS
÷
×
x I
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
TOC/IDMT calculation
1MRK 511 358-UEN A
(Equation 99)
(Equation 100)
(Equation 101)
(Equation 102)
Application manual