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
op
P
t
TD
A
B
M
C
=
×
æ
ö
+
ç
÷
-
è
ø
EQUATION1745-ANSI V1 EN-US
(Equation 492)
where:
t
op
is the operating time in seconds of the Inverse Time Overcurrent TOC/IDMT algorithm
TD
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
characteristic of the OC1 step in it is obvious that if the following rules are followed:
1. set TD equal to the IEC or ANSI standard generator capability value
2. set parameter
A_OC1
equal to the value 1/x2
3. set parameter
C_OC1
equal to the value 1/x2
4. set parameters
B_OC1
= 0.0 and
P_OC1
=2.0
5. set
PickupCurr_OC1
equal to the value x
then the OC1 step of the CVGAPC function can be used for generator negative
sequence inverse overcurrent protection.
1. select positive sequence current as measuring quantity for this CVGAPC function
2. make sure that the base current value for CVGAPC function is equal to the
generator rated current
3. set TD = 37.5 for the IEC standard or TD = 41.4 for the ANSI standard
4. set
A_OC1
= 1/1.162 = 0.7432
5. set
C_OC1
= 1/1.162 = 0.7432
6. set
B_OC1
= 0.0 and
P_OC1
= 2.0
7. set
PickupCurr_OC1
= 116%
1MRK 504 163-UUS A
Section 12
Multipurpose protection
Transformer protection RET670 2.2 ANSI
655
Application manual
Содержание RELION RET670
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