Upol = -2U
0
I>Dir
RCA
Operation
IEC16000027-1-en.vsdx
IEC16000027 V1 EN-US
Figure 56: Relay characteristic angle given in degree
In a normal transmission network a normal value of RCA is about 65°.
Normally voltage polarizing from the internally calculated residual sum or an
external open delta is used.
UPolMin: Minimum polarization (reference) polarizing voltage for the directional
function, given in % of UBase/2.
I>Dir: Operate residual current release level in % of IB for directional stage. The
setting is given in % of IB. The output signals, STFW and STRV can be used in a
teleprotection scheme. The appropriate signal should be configured to the
communication scheme block.
8.4.3.3 2nd harmonic restrain
M15282-90 v6
If a power transformer is energized there is a risk that the current transformer core
will saturate during part of the period, resulting in a transformer inrush 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 residual overcurrent function
will give an unwanted trip. The inrush current has a relatively large ratio of 2nd
harmonic component. This component can be used to create a restrain signal to
prevent this unwanted function.
At current transformer saturation a false residual current can be measured by the
protection. Here the 2
nd
harmonic restrain can prevent unwanted operation as well.
1MRK 506 375-UEN A Section 8
Current protection
Railway application RER670 2.2 IEC 173
Application manual
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