ABB REL670 2.2 IEC - Setting of Minimum Operate Currents

8.4.3.10 Setting of minimum operate currents
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The operation of the distance function will be blocked if the magnitude of the
currents is below the set value of the parameter IMinOpPP and IMinOpPE.
The default setting of IMinOpPP and IMinOpPE is 20% of IBase where IBase is
the chosen base current for the analog input channels. The values have been proven
in practice to be suitable in most of the applications. However, there might be
applications where it is necessary to increase the sensitivity by reducing the
minimum operate current down to 10% of IBase.
The minimum operate fault current is automatically reduced to 75% of its set value,
if the distance protection zone has been set for the operation in reverse direction.
8.4.3.11 Setting of directional mode
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Setting of the directional mode is by default set to forward by setting the parameter
DirMode to Forward.
The selection of Offset mho can be used for sending block signal in blocking
teleprotection scheme, switch onto fault application and so on.
The Reverse mode might be use in comparison schemes where it is necessary to
absolute discriminate between forward and reverse fault.
8.4.3.12 Setting of direction for offset mho
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If offset mho has been selected, one can select if the offset mho shall be Non-
Directional, Forward or Reverse by setting the parameter OfffsetMhoDir.
When forward or reverse operation is selected, then the operation characteristic
will be cut off by the directional lines used for the mho characteristic. The setting is
by default set to Non-Directional.
8.4.3.13 Setting of timers for distance protection zones
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The required time delays for different distance protection zones are independent of
each other. Distance protection zone 1 can also have a time delay if so required for
selectivity reasons. One can set the time delays for all zones in a range of 0 to 60
seconds. The tripping function of each particular zone can be inhibited by setting
the corresponding Operation parameter to Off.
Different time delays are possible for the phase-to-earth tPE and for the phase-to-
phase tPP measuring loops in each distance protection zone separately, to further
increase the total flexibility of a distance protection.
In the case of evolving faults or momentary current transformer saturation
conditions, the pick up of the zones may get delayed. Zone timer logic improves
the operating time in such conditions. The zone timer logic can be set using the
Section 8 1MRK 506 369-UEN B
Impedance protection
260 Line distance protection REL670 2.2 IEC
Application manual