defined as the percentage value of DI
diff
/
DI
Bias
, is proposed to be set to 80 %, if no
deeper analysis is done.
IdUnre: IdUnre is the sensitivity of the unrestrained differential protection stage. The
choice of setting value can be based on calculation of the largest short circuit current
from the generator at fault in the external power system (normally three-phase short
circuit just outside of the protection zone on the LV side of the step-up transformer).
IdUnre is set as a multiple of the generator rated current.
OpCrossBlock: If OpCrossBlock is set to Yes, and PICKUP signal is active, activation
of the harmonic blocking in that phase will block the other phases as well.
7.3.3.3 Negative sequence internal/external fault discriminator feature
SEMOD155693-41 v3
OpNegSeqDiff: OpNegSeqDiff is set to Yes for activation of the negative sequence
differential features, both the internal or external fault discrimination and the sensitive
negative sequence differential current feature. It is recommended to have this feature
enabled.
IMinNegSeq: IMinNegSeq is the setting of the smallest negative sequence current when
the negative sequence based functions shall be active. This sensitivity can normally be
set down to 0.04 times the generator rated current, to enable very sensitive protection
function. As the sensitive negative sequence differential protection function is blocked
at high currents the high sensitivity does not give risk of unwanted function.
NegSeqROA: NegSeqROA is the “Relay Operate Angle”, as described in figure
69.
The default value 60° is recommended as optimum value for dependability and
security
.
Section 7 1MRK 502 071-UUS A
Differential protection
182 Generator protection REG670 2.2 ANSI and Injection equipment REX060, REX061, REX062
Application manual
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