The 2Nd And 5Th Harmonic Analysis - ABB RED650 Applications Manual

1MRK 505 393-UEN B
6.1.3.3
Line differential protection RED650 2.2 IEC
Application manual
EndSection1
EndSection1 is set as a multiple of IBase. The default value 1.25 is generally
recommended. If the conditions are known more in detail, other values can be
chosen in order to increase or decrease the sensitivity.
EndSection2
EndSection2 is set as a multiple of IBase. The default value 3.00 is generally
recommended. If the conditions are known more in detail, other values can be
chosen in order to increase or decrease the sensitivity.
SlopeSection2
SlopeSection2 is set as a percentage value: [delta operate current/delta restrain
current] × 100%. The default value 40.0 is generally recommended. If the
conditions are known more in detail, other values can be chosen in order to
increase or decrease the sensitivity.
SlopeSection3
SlopeSection3 is set as a percentage value: [delta operate current/delta restrain
current] × 100%. The default value 80.0 is generally recommended. If the
conditions are known more in detail, other values can be chosen in order to
increase or decrease the sensitivity.

The 2nd and 5th harmonic analysis

nd th
The 2 and 5 harmonic block scheme is permanently active only if an in-line
power transformer (A or B, alternatively both A and B) is part of the protected
circuit. This is a must due to phenomena specific for power transformers, such as
inrush and over-excitation. If there is no power transformer included in the
protected multi-terminal line circuit, then the 2
only active under the following conditions:
• If the bias current is lower than 1.25 times IBase.
• Under external fault conditions.
• If NegSeqDiffEn = Off (the default is On )
When the harmonic content is above the set level, the restrained differential
operation is blocked. However, if a fault has been classified as internal by the
negative sequence fault discriminator, any harmonic restraint is overridden.
I2/I1Ratio
The set value is the ratio of the 2
to the fundamental frequency component of the differential current. To obtain this
information, the instantaneous differential current must be analyzed.
Transformer inrush currents cause high degrees of the 2
differential current. The default value of 15% is a reliable value to detect power
transformer inrush currents.
Differential protection
nd th
and 5
nd
harmonic component of the differential current
nd
Section 6
M12541-186 v3
M12541-189 v3
M12541-192 v4
M12541-195 v4
M12541-198 v5
harmonic block scheme is
M12541-201 v4
harmonic in the
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