Nd Harmonic Restrain - ABB REL650 Applications Manual

1MRK 506 334-UUS A
7.3.3.2
Application manual
parameter the operation time of the step can never be shorter than the setting. Setting
range: 0.000 - 60.000s in steps of 0.001s.
Operate time
tx
tnMin
IMinn
IEC09000164 V2 EN
Figure 87: Minimum operate current and operation time for inverse time
characteristics
In order to fully comply with curves definition setting parameter tnMin shall be set to the
value, which is equal to the operating time of the selected inverse curve for measured
current of twenty times the set current pickup value. Note that the operating time value is
dependent on the selected setting value for time multiplier TDn.
HarmRestrainx: Enable block of step n from the harmonic restrain function (2nd
harmonic). This function should be used when there is a risk if power transformer inrush
currents might cause unwanted trip. Can be set Disabled/Enabled.

2nd harmonic restrain

If a power transformer is energized there is a risk that the transformer core will saturate
during part of the period, resulting in an inrush transformer current. This will give a
declining residual current in the network, as the inrush current is deviating between the
phases. There is a risk that the phase overcurrent function will give an unwanted trip. The
inrush current has a relatively large ratio of 2
be used to create a restrain signal to prevent this unwanted function.
The settings for the 2nd harmonic restrain are described below.
Current protection
Current
IEC09000164-2
nd
harmonic component. This component can
Section 7
183