Hitachi Relion 670 Series Applications Manual page 146

Section 7
Impedance protection
IMinOp: To select the minimum operating current for underimpedance element. If the minimum
current is exceeded, underimpedance protection calculates the impedance. A default setting of 10%
of IB is recommended.
Zone 1
OpModeZ1: To select the operating characteristic of zone 1 underimpedance element. This can be
selected as Off/Mho offset/Quad non-dir.
Z1Fwd: To set the zone 1 forward positive sequence impedance reach in ohm/p. It is recommended
to set this to 70% of transformer impedance.
Z1Rev: To set the zone 1 reverse positive sequence impedance reach in ohm/p. This should be set
as 1% of transformer impedance or lower for better security in case of reverse faults.
RFFwZ1: To set the zone 1 forward fault resistive reach in ohm/p when quadrilateral characteristic is
chosen. It should be set to give maximum coverage of fault resistance and the load encroachment
(R ).
Ldmax

R
Ld max
IECEQUATION226 V2 EN-US
RFRevZ1: To set the zone 1 reverse fault resistive reach in ohm/p when quadrilateral characteristic is
chosen. It may be set identical to RFFwZ1.
tZ1: To set the zone 1 time delay to trip. Default setting is 0.0s.
Zone 2
OpModeZ2: To select the operating characteristic of zone 2 distance element. This can be selected
as Off/Mho offset/Quad non-dir.
Z2Fwd: To set the zone 2 forward positive sequence impedance reach in ohm/p. It is recommended
to set this to 125% of transformer impedance.
Z2Rev: To set the zone 2 reverse positive sequence impedance reach in ohm/p. The recommended
setting is 80% of shortest outgoing line in the reverse direction in order to cover the bus faults.
RFFwZ2: To set the zone 2 forward fault resistive reach in ohm/p if quadrilateral characteristic is
selected. It should be set to give maximum coverage of fault resistance and the load encroachment
(R ).
Ldmax
RFRevZ2: To set the zone 2 reverse fault resistive reach in ohm/p if quadrilateral characteristic is
selected. It may be set identical to RFFwZ2.
tZ2: To set the zone 2 time delay to trip. The default setting is 0.5s. It should be set to coordinate with
clearance of adjacent circuit fault within reach by the intended main protection or breaker fail
protection.
Zone 3
OpModeZ3: To select the operating characteristic of the zone 3 distance element. This can be
selected as Off/Mho offset/Quad non-dir.
Z3Fwd: To set the zone 3 forward positive sequence impedance reach in ohm/p. It should be set to
overreach the remote terminal of the longest adjacent line about 20% for all fault conditions.
Z3Rev: To set the zone 3 reverse positive sequence impedance reach in ohm/p. This may be set
identical to Z2Rev.
140
U
min
I
max
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1MRK506375-UEN Rev. N
(Equation 35)
Railway application RER670
Application manual