ABB Relion REQ650, Applications Manual

Page: 183 / 340

3 2
3 2 100
=
< ×
I
I
IBase
EQUATION1520 V3 EN
(Equation 73)
where:
3I2
is the maximal negative sequence current during normal operating conditions, plus a margin of
10...20%
IBase
is the setting of base current for the function
9.2.3.4 Zero sequence based
The relay setting value 3U0> is given in percentage of the global parameter UBase .
The setting of 3U0> should not be set lower than according to equation 74 .
3 0
3 0 100
U
U
UBase
>= ×
EQUATION1521 V2 EN
(Equation 74)
where:
3U0
is the maximal zero sequence voltage during normal operation conditions, plus a margin of
10...20%
UBase is setting of global base voltage all functions in the IED.
The setting of the current limit 3I0< is done in percentage of the global parameter
IBase . The setting of 3I0< must be higher than the normal unbalance current that
might exist in the system. The setting can be calculated according to equation 75 .
3 0
3 0 100
= ×
<
I
I
IBase
EQUATION2293 V2 EN
(Equation 75)
where:
3I0<
is the maximal zero sequence current during normal operating conditions, plus a margin of
10...20%
IBase is setting of global base current all functions in the IED.
9.2.3.5 Delta U and delta I
Set the operation mode selector OpDUDI to On if the delta function shall be in
operation.
The setting of DU> should be set high (approximately 60% of UBase ) and the current
threshold DI< low (approximately 10% of IBase ) to avoid unwanted operation due to
1MRK 505 291-UEN A
Section 9
Secondary system supervision
177
Application manual