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:
2
1
op
m
r
k
t
I
I
=
æ
ö
-
ç
÷
è
ø
EQUATION1376 V1 EN
(Equation 253)
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:
x = 116% = 1.16
pu
EQUATION1377 V2 EN
(Equation 254)
formula 3.5can be re-written in the following way without changing the value for the
operate time of the generator stator overload IED:
2
2
2
1
1
op
m
r
k
x
t
I
x I
x
×
=
æ
ö
-
ç
÷
×
è
ø
EQUATION1378 V1 EN
(Equation 255)
1MRK 502 071-UEN -
Section 12
Multipurpose protection
Generator protection REG670 2.2 IEC and Injection equipment REX060, REX061, REX062
455
Application manual
Содержание Relion REG670
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