GE UR Series L90 Instruction Manual page 452

5.7 CONTROL ELEMENTS
• GND DIR O/C REV: This setting defines the FlexLogic operand (if any) of a protection element that is used in addition
to zone 4 for identifying reverse faults, and thus, for initiating the blocking signal. Either reverse-looking directional or
non-directional overcurrent protection element may be used as
Even though any FlexLogic operand could be used as
ious protection elements or to apply extra conditions through FlexLogic equations, this extra signal is primarily meant
to be the output operand from either the negative-sequence directional, neutral directional, or a non-directional instan-
taneous overcurrent element.
The selected protection element (or elements in combination) should be coordinated with the selection of
. For all the forward external faults seen by an element used as
FWD
reverse-looking element used as
greater security and to overcome spurious directional element operation during transients, adding a pickup delay
greater than the pilot channel delay to the reverse directional element is recommended.
• BLOCK SCHEME NO OF COMM BITS: This setting specifies the number of bits of the communications channel avail-
able for the scheme. With only one bit available, the scheme sends the blocking signal by asserting the
FlexLogic operand. This operand should be used to start the channel (set the blocking signal). On internal faults,
INIT
the scheme removes the blocking signal by asserting the
For tripping the scheme responds to lack of the blocking signal on bit 1 (
only local fault type identification provided by the phase selector to assert the output operands
and . Please refer to the Theory of operation chapter for more information on communications.
3P
To take advantage of the four-bit blocking scheme, the blocking signals should be initiated from a disturbance detector.
This can be accomplished by using both
cific bits will be de-asserted by the scheme based on the phase selection providing the peer relay with more informa-
tion on the fault type. Otherwise, the peer relay issues a three-pole trip upon receiving the bit pattern (0, 0, 0, 0).
5
• BLOCK SCHEME RX1 through BLOCK SCHEME RX4: These settings allow the user to select the FlexLogic oper-
ands that represent the receive signals for the scheme. Typically input contacts interfacing with a signaling system are
used. In single-bit applications,
BLOCK SCHEME RX2
, and
RX3 BLOCK SCHEME RX4
5-314
GND DIR O/C REV
and
50DD
BLOCK SCHEME RX1
must be used. In four-bit applications,
must be used.
L90 Line Current Differential System
.
GND DIR O/C REV
, enabling the user to combine responses of var-
GND DIR O/C REV
GND DIR O/C FWD
at the other end should pickup and provide a blocking signal. For
FlexLogic operand.
DIR BLOCK TX1
BLOCK SCHEME RX1
to assert the blocking signal. Subsequently, spe-
DIR BLOCK TX INIT
must be used. In two-bit applications,
,
BLOCK SCHEME RX1
5 SETTINGS
GND DIR O/C
at one end of the line, the
DIR BLOCK TX
setting). The scheme uses
DIR BLOCK TRIP A
BLOCK SCHEME RX1
,
BLOCK SCHEME RX2 BLOCK SCHEME
GE Multilin
, ,
B C
and