ABB ETL600 Instruction Manual page 115

ETL600
the test is repeated and alarm is given should the results of three
subsequent trials be negative.
The loop test signal is transmitted with a test tone level of 0 dBm0 or
with the guard level (whatever is higher). The first cyclic loop test is
sent 10 minutes after power-on the equipment.
In case the TPE is operated in an APLC channel, the speech and the
guard signal in the TPE channel are switched off, the ETL pilot signal
and superimposed data channels remain active during a cyclic loop
test. Exceptions:
•
If no speech is configured in the TPE channel, the disconnectable
data channels are switched off to obtain the necessary transmitter
power.
•
If the TPE uses the ETL pilot as guard signal, it will be switched off
by the cyclic loop test.
In case the TPE is operated in the DPLC channel, the MOD600 signal
and the pilot/guard signal in the DPLC channel are switched off during
the cyclic loop test.
Providing the cyclic loop test is enabled by HMI600, a test signal with
its own frequency is transmitted to the opposite station and reflected
back once – depending on the programming - every 1/3/6/12/24 hours.
The test signal is processed in the same way as a normal tripping
signal (interruption of the guard signal and transmission of a test
frequency for 3 x T0). The reception of the reflected signal must take
place between 0.5 x T0 and 10 x T0 after sending it, which ensures
that all the functions required for transmitting a tripping signal are fully
tested.
In case an automatically initiated test is not correctly received results
in it being repeated at intervals of about 5 minutes until either the
remote station answers or a continuous alarm is given after the third
attempt. Note that, quality of the transmission channel permitted, the
loop test can be correctly executed even if the guard signal is
permanently lost. The loss of the guard signal is, however, signaled by
both ETL600 and NSD600.
The testing facilities impair in no way the ability of the equipment to
respond to a protection command, i.e. a genuine tripping command is
always given priority over all tests.
If a cyclic loop test can not be sent regularly due to a command being
transmitted at that time, the NSD600 will try to resend it in intervals of
1 minute. An event recorder entry does only take place when the loop
test could actually be released, i.e. after the command transmission
has stopped.
The loop test includes automated measurement of the transmission
time, i.e. half the measured transmission time for both directions there
and back plus a delay for one relay interface input and output circuit is
recorded.
Structure and Function
1KHW001489-EN
November 2005
ABB Switzerland Ltd
3-83