EQUATION1372 V1 EN-US (Equation 99)
where:
t
op
is the operating time in seconds of the negative sequence overcurrent IED
k is the generator capability constant in seconds
I
NS
is the measured negative sequence current
I
r
is the generator rated current
By defining parameter x equal to maximum continuous negative sequence rating of the
generator in accordance with the following formula
EQUATION1373 V1 EN-US (Equation 100)
Equation 99 can be re-written in the following way without changing the value for the operate
time of the negative sequence inverse overcurrent IED:
2
2
1
op
NS
r
k
x
t
I
x I
×
=
æ ö
ç ÷
×
è ø
EQUATION1374 V1 EN-US (Equation 101)
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
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-US (Equation 102)
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
Section 10 1MRK 511 358-UEN A
Multipurpose protection
206
Application manual
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