4.
set
A_OC1
= 1/0.07
2
= 204.0816
5. set
B_OC1
= 0.0, C_OC1 = 0.0 and
P_OC1
= 2.0
6. set
StartCurr_OC1
= 7%
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).
10.1.3.3 Generator stator overload protection in accordance with IEC or ANSI
standards
M13088-81 v3
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:
EQUATION1376 V1 EN-US (Equation 80)
where:
t
op
is the operating time of the generator stator overload IED
k 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)
I
m
is the magnitude of the measured current
I
r
is the generator rated current
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).
By defining parameter x equal to the per unit value for the desired pickup for the overload IED
in accordance with the following formula:
EQUATION1377 V2 EN-US
(Equation 81)
formula 3.5can be re-written in the following way without changing the value for the operate
time of the generator stator overload IED:
1MRK 505 370-UEN D Section 10
Multipurpose protection
Busbar protection REB670 233
Application manual
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