ABB RELION 650 SERIES, Applications Manual

Page: 81 / 262

IEC09000164-2
Operate time
Current
tx
tnMin
IMinn
IEC09000164 V2 EN-US
Figure 29: 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.
7.1.3.2 2nd harmonic restrain
M12982-91 v7
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
nd
harmonic component. This component can be used to create a restrain signal to
prevent this unwanted function.
The settings for the 2nd harmonic restrain are described below.
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.
1MRK 505 287-UUS B Section 7
Current protection
Busbar protection REB650 75
Application manual
© Copyright 2013 ABB. All rights reserved