ABB Relion 670 Series Applications Manual page 297

1MRK 511 401-UEN Rev. K
1. set k 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
Proper timing of the CVGAPC function made in this way can easily be verified by secondary
injection. All other settings can be left at the default values. If required delayed time reset for
OC1 step can be set in order to ensure proper function operation in case of repetitive
unbalance conditions.
Furthermore the other built-in protection elements can be used for other protection and
alarming purposes (for example, use OC2 for negative sequence overcurrent alarm and OV1 for
negative sequence overvoltage alarm).
12.1.3.3 Generator stator overload protection in accordance with IEC or ANSI
standards
Example will be given how to use one CVGAPC function to provide generator stator overload
protection in accordance with IEC or ANSI standard if minimum-operating current shall be set
to 116% of generator rating.
The generator stator overload protection is defined by IEC or ANSI standard for turbo
generators in accordance with the following formula:
=
t
op
æ
ç
è
EQUATION1376 V1 EN-US
where:
t
op
k
I
m
I
r
This formula is applicable only when measured current (for example, positive sequence
current) exceeds a pre-set value (typically in the range from 105 to 125% of the generator rated
current).
Bay control REC670
Application manual
A_OC1 equal to the value 1/x2
B_OC1 = 0.0, C_OC1 =0.0 and P_OC1 =2.0
StartCurr_OC1 equal to the value x
k_OC1 = 20
2
A_OC1 = 1/0.07 = 204.0816
B_OC1 = 0.0, C_OC1 = 0.0 and P_OC1 = 2.0
StartCurr_OC1 = 7%
k
2
ö
I
-
1
m
÷
I
ø
r
is the operating time of the generator stator overload IED
is the generator capability constant in accordance with the relevant standard (k = 37.5 for the IEC
standard or k = 41.4 for the ANSI standard)
is the magnitude of the measured current
is the generator rated current
© Copyright 2017 Hitachi Power Grids. All rights reserved
Section 12
Multipurpose protection
M13088-81 v3
(Equation 169)
291