Transit Filters - ABB ETL600 Instruction Manual

ETL600
signal interruptions (typically less than 100 ms) caused by
teleprotection command transmission in mode 'disconnectable'
cannot be tolerated. As a consequence, the available power for
teleprotection command signals is reduced accordingly.
For more information on the management of signal levels for
teleprotection, refer to section 3.4.3 'External teleprotection' and to
section 5.2.16 'Signal boosting for teleprotection devices'.
3.4.2.2.

Transit filters

The frequency bands of the signals injected into the teleoperation input
ports are subject to the following restrictions:
•
Each frequency band must lie in the range from 300 to 4000 Hz.
•
The frequency bands must not overlap.
•
The frequency bands must not overlap the pilot band.
•
The frequency bands must not overlap the speech band, if speech
is used.
•
The frequency bands must not overlap the NSD600 guard signal
band, if NSD600 is used with own guard signal.
Refer to Fig. 3-6, Fig. 3-7 and Fig. 3-8 for information about the
frequency bands occupied by speech, pilot or NSD600 guard.
To ensure that the signals injected into the teleoperation input ports do
not violate the above restrictions, frequency selective filters called
'transit filters' can be inserted into the input or output ports. A large
number of frequency characteristics, some of them equalized for low
group delay variation, are available for each of these transit filters,
(Fig. 3-34). A maximum of two transit filters are available on each
O4LE board when speech is configured. When no speech is
configured, a maximum of four transit filters per O4LE board are
supported.
SPEECH BAND
0
Fig. 3-34
If the AF signal of a first ETL-link has to be forwarded to a second link
via teleoperation ports – this is called 'transit operation' -, the pilot
Structure and Function
1KHW001489-EN
1 2
Transit filter cutoff frequencies selectable in steps of
60 Hz
ABB Switzerland Ltd
3 4 kHz
November 2005 3-43