ABB REL650 Applications Manual page 190

Section 7
Current protection
184
2ndHarmStab: The rate of 2nd harmonic current content for activation of the 2nd
harmonic restrain signal, to block chosen steps. The setting is given in % of the
fundamental frequency residual current. The setting range is 5 - 100% in steps of 1%. The
default setting is 20% and can be used if a deeper investigation shows that no other value
is needed..
HarmRestrainx: This parameter can be set Disabled/Enabled, to disable or enable the 2nd
harmonic restrain.
The four step phase overcurrent protection 3-phase output can be used in different ways,
depending on the application where the protection is used. A general description is given
below.
The pickup current setting of the inverse time protection, or the lowest current step of the
definite time protection, must be defined so that the highest possible load current does not
cause protection operation. Here consideration also has to be taken to the protection reset
current, so that a short peak of overcurrent does not cause operation of the protection even
when the overcurrent has ceased. This phenomenon is described in figure 88.
Current I
Pickup current
Reset current
The IED does not reset
ANSI09000146 V1 EN
Figure 88: Pickup and reset current for an overcurrent protection
The lowest setting value can be written according to equation 106.
1MRK 506 334-UUS A
Line phase current
Time t
ANSI09000146-en-1.vsd
Application manual