ABB RELION RET670 Applications Manual page 258

Section 8
Impedance protection
252
Reactive reach
The reactive reach in forward direction must as minimum be set to cover the measuring
zone used in the Teleprotection schemes, mostly zone 2. Equation
equation 103 gives the minimum recommended reactive reach.
³ ×
X1 1.44 X1
PHS Zm
EQUATION1309 V1 EN-US
³ ×
X0 1.44 X0
PHS Zm
EQUATION1310 V1 EN-US
where:
X1 is the reactive reach for the zone to be covered by FDPSPDIS (21), and the constant
Zm
1.44 is a safety margin
X0 is the zero-sequence reactive reach for the zone to be covered by FDPSPDIS (21)
Zm
The reactive reach in reverse direction is automatically set to the same reach as for
forward direction. No additional setting is required.
Fault resistance reach
The resistive reach must cover RFPG for the overreaching zone to be covered, mostly
zone 2. Consider the longest overreaching zone if correct fault selection is important in
the application. Equation
³ ×
1.1 RFPG
RFltFwdPG
min
EQUATION1724 V2 EN-US
where:
RFPG RFPG for the longest overreaching zone to be covered by FDPSPDIS (21).
is the setting
Zm
The security margin has to be increased to at least 1.2 in the case where φloop<60° to
avoid that FDPSPDIS (21) characteristic shall cut off some part of the zone
measurement characteristic.
Phase-to-ground fault in reverse direction
Reactive reach
The reactive reach in reverse direction is the same as for forward so no additional
setting is required.
104 gives the minimum recommended resistive reach.
zm
1MRK 504 163-UUS A
102 and
(Equation 102)
(Equation 103)
(Equation 104)
Transformer protection RET670 2.2 ANSI
Application manual
M13142-9 v4
M13142-103 v5
M13142-151 v4
M13142-153 v2