ABB RELION RET670, Applications Manual

Page: 318 / 1016

8.5.3.8 Load impedance limitation, with load encroachment function activated
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The parameters for load encroachment shaping of the characteristic are found in the
description of the phase selection with load encroachment function, section
"Resistive
reach with load encroachment characteristic" . If the characteristic for the impedance
measurement shall be shaped with the load encroachment algorithm, the parameter
OperationLdCmp in the phase selection has to be switched On .
8.5.3.9 Setting of minimum operating 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
IMinOpPE .
The default setting of IMinOpPE is 20% of IBase where IBase is the chosen base
current for the analogue input channels. The value 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 operating current down
to 10% of the IED base current. This happens especially in cases, when the IED serves
as a remote back-up protection on series of very long transmission lines.
If the load current compensation is activated, there is an additional criteria IMinOpIN
that will block the phase-ground loop if the 3I0< IMinOpIN . The default setting of
IMinOpIN is 5% of the IED base current IBase .
The minimum operating 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.
8.5.3.10 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 zone1 can also have a time delay, if so required for
selectivity reasons. One can set the time delays for all zones (basic and optional) 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 ph-E ( tPE ) measuring loops in each distance protection zone
separately, to further increase the total flexibility of a distance protection.
8.6 Additional distance protection directional function for
earth faults ZDARDIR
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Section 8
1MRK 504 163-UUS A
Impedance protection
312 Transformer protection RET670 2.2 ANSI
Application manual