Channel Monitor; Loopback Test; Direct Transfer Tripping - GE UR Series Instruction Manual

2.2 PILOT CHANNEL
In the Peer to Peer mode, all L90 relays act as Masters.
2
The L90 has logic to detect that the communications channel is deteriorating or has failed completely. This can provide an
alarm indication and disable the current differential protection. Note that a failure of the communications from the Master to
a Slave does not prevent the Master from performing the current differential algorithm; failure of the communications from a
Slave to the Master will prevent the Master from performing the correct current differential logic. Channel propagation delay
is being continuously measured and adjusted according to changes in the communications path. Every relay on the protec-
tion system can assigned an unique ID to prevent advertent loopbacks at multiplexed channels.
This option allows the user to test the relay at one terminal of the line by "looping" the transmitter output to the receiver
input; at the same time, the signal sent to the remote will not change. A local loopback feature is included in the relay to
simplify single ended testing.
The L90 includes provision for sending and receiving a single-pole Direct Transfer Trip (DTT) signal from current differential
protection between the L90 relays at the terminals of the line using the pilot communications channel. The user may also
initiate an additional 8 pilot signals with an L90 communications channel to create trip/block/signaling logic. A FlexLogic™
operand, an external contact closure, or a signal over the LAN communication channels can be assigned for that logic.
2-8
Tx
Rx
L90 - 1
Tx
OPTIONAL REDUNDANT CHANNEL
Rx
TYPICAL 2-TERMINAL APPLICATION
Tx
Rx
L90 - 1
Tx
Rx
TYPICAL 3-TERMINAL APPLICATION
Figure 2–2: COMMUNICATION PATHS DIAGRAM
L90 Line Differential Relay
2 PRODUCT DESCRIPTION
Rx
Tx
L90 - 2
Rx
Tx
Rx
Tx
L90 - 2
Rx
Tx
Tx Rx Tx Rx
CHn CHn
L90 - 3

2.2.4 DIRECT TRANSFER TRIPPING

831009A4.CDR

2.2.2 CHANNEL MONITOR

2.2.3 LOOPBACK TEST

GE Power Management