Generator Stator Overload Protection In Accordance With Iec Or Ansi Standards - ABB REC670 Applications Manual

1MRK 511 401-UEN A
11.1.3.3
Bay control REC670 2.2 IEC
Application manual
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 k_OC1 = 20
4.
set A_OC1= 1/0.07
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).
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:
k
=
t
op
2
æ ö
I
-
m 1
ç ÷
I
è ø
r
EQUATION1376 V1 EN-US
where:
t is the operating time of the generator stator overload IED
op
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 is the magnitude of the measured current
m
I is the generator rated current
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).
2
= 204.0816
Section 11
Multipurpose protection
(Equation 100)
M13088-81 v3
263