Special Application Consideration - Ametek UPLC CU44-VER04 Applications Manual

UPLC™ Application Manual
3.6 Special Application
Considerations
Because the UPLC™ is "ON/OFF" modulated,
only one frequency (f C ) is required for line protec-
tion. When applied to three terminal lines, phase
cancellation will occur when two or more transmit-
ters are keyed simultaneously. To prevent this, you
should offset transmitters by ±100Hz, using the
thumbwheel frequency programming switches. The
three frequencies should be:
• f C
• f C - 100Hz
• f C + 100Hz
The UPLC™ does not have an adjustable filter or
hybrid attached to the output of the transmitter.
If you are using the UPLC™ in an ON-OFF appli-
cation where no other power line carrier equipment
is attached to the power line, then no further action
is required. However, in the application of Single
Comparator Phase Comparison relaying, the
UPLC™ is to be operated in the four-wire mode,
with an external skewed hybrid between trans-
mitter and receiver.
Page 3–36
If you are applying the carrier set with other trans-
mitters, coupled through the same tuning equip-
ment, you must apply a hybrid or a series LC unit to
the transmitter output to isolate the other transmit-
ters from the UPLC™ transmitter. This will avoid
the problems of intermodulation distortion. We sug-
gest that you use a hybrid if the frequency spacing
between all transmitters is within the bandwidth of
the hybrid (usually 6%). Check the manufacturers
instructions for the actual spacing limitations of the
hybrid you are using. If you cannot use a hybrid,
then you may use a series LC unit to isolate the
transmitters. In this case, the transmitters must have
spacing such that the LC you are using will attenu-
ate the external frequencies by at least 20dB (if the
other frequency is a 10 watt transmitter), and 30dB
(if the other frequency is a 100 watt transmitter).