ABB ETL600, Instruction Manual

Page: 114 / 382

ABB Switzerland Ltd
1KHW001489-EN ETL600
No alarm condition pick-up time and no hold time for the command
outputs according to d) can be configured. Received commands are
immediately “frozen” in case of a link failure, they are only removed
from the command outputs if a valid guard signal or an other command
signal is detected again.
3.6.8.10. Tx Command Acknowledge
Each injected Tx command A to D can be reflected from the
processing unit P4LT to one of the various outputs on the
teleprotection interfaces type G4AI (configurable by means of the
HMI600) to acknowledge that the corresponding command was sent
(e.g. Tx Cmd A Ack). This is, however, no confirmation that the
command has also been received by the opposite station.
Each of the acknowledging outputs is operated as long as the
corresponding commands are sent (incl. Tx input command delay and
Tx input command prolongation).
3.6.8.11. Rx Guard Signaling
The state of the NSD600 guard receiver can be signaled by the RF
converter type P4LT to one of the various outputs on the teleprotection
interface type G4AI (configurable by means of the HMI600). Reception
of the ETL600 pilot signal (when used as guard signal) or the own
NSD600 guard with adequate signal quality means that the
corresponding solid state output is closed or the coil of the selected
relay contact is energized.
Note:
No pick up or hold times are programmable for the
Rx guard output.
Therefore, outputs configured for Rx guard may
bounce for certain Rx levels or signal to noise ratios.
3.6.8.12. Blocking of AGC
If the NSD600 receiver accepts the signal as a genuine tripping
command (no ETL-pilot signal and a tripping signal at the proper
frequencies in the speech band), speech in the corresponding APLC
channel is interrupted and the automatic gain control (AGC) in this
channel and in all APLC channels without an internal TPE is blocked.
The latter is necessary to prevent the ETL600 gain from increasing as
a result of the missing pilot signal whilst tripping signals are being
received.
If the NSD600 uses an own guard signal, the AGC will not be blocked
during command reception.
3.6.8.13. Cyclic Loop Test
An cyclic loop test sequentially checks the integrity of the
teleprotection channel. The test signal simulates the transmission of a
genuine tripping signal and is recognized as such at the receiving end,
from whence it is echoed back to the transmitter. The test is deemed
successfully, providing the transmitter receives the echo. If it does not,
3-82 November 2005 Structure and Function