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Communication-capable Circuit Breakers
WL Circuit Breaker
The trigger event can be set
individually for each waveform
buffer. The point at which the
trigger event is to take place in the
waveform buffer can also be defined.
This setting can be used to set the
ratio of the pre-event history to the
post-event history. If the pre-trigger
event history is to be analyzed, the
position can be set to 80%. When
the event occurs, 0.8 seconds of
pre-event history and 0.2 seconds
of post-event history are available in
the waveform buffer, and an existing
COM15 module adds a time stamp
to the trigger event.
Each waveform buffer stops
independently, depending on the
trigger event and can be activated
again once the analysis is complete.
A large amount of data (approx.
25 kByte for each waveform) can
be downloaded and analyzed using
the BDA and the ETU776 display.
Depending on the option, a range of
zoom options and export functions
are available.
Voltage Transformers
For isolation reasons, a voltage
transformer is used in conjunction
with the Metering Function module
and Metering Function Plus module.
This prevents voltage signals of up to
1kV from reaching the ETU directly
via the auxiliary secondary
connections.
A suggested voltage transformer
is the ITI Model 450 with a 120V
secondary and 600V max. primary.
(See Chart 2-1 on page 2/13.)
The voltage transformer can be wye
or delta-connected on the primary
side. On the secondary side, a wye
connection is always used to connect
it to the auxiliary secondary
connector (X7.5 to X7.8). See
Fig. 2-7.
If the level of accuracy specified in
Table 2-7 is to be attained, a class 0.5
2/15
voltage transformer must be
used. The burden of the metering
function is 27kΩ, which means
that up to 6 metering modules can
be connected simultaneously to a
voltage transformer with an apparent
power of 2.5VA (pay attention to
the accuracy class and length of
the connection cable to guarantee
accuracy).
The accuracy of the voltage
measurement depends on the
number of metering modules
connected per voltage transformer:
• Class 0.5 for 1 to 3 metering
modules
• Class 3 for 4 to 6 metering
modules
This data applies to ambient
temperatures from 30ºC to 50ºC and
a primary voltage from 80% to 120%
V
.
n
Maximum distance from voltage
transformer
The maximum distance between the
metering function and the voltage
transformer depends on the cable
size and the desired accuracy class.
The diagram illustrates how the voltage transformer is connected for operation with a
Figure
metering function. The transformer can be wye or delta-connected on the primary side.
2-7
WL PROFIBUS Communication and Electronic Accessories • July 2004
For a 14AWG cable, the maximum
distance should not exceed 50 m
for class 0.5 and 100 m for class 3.
In areas with high EMC exposure,
shielded cable should be used.
Parameters for the settings of the
metering function
To calculate the measured values,
the voltage transformer data must
be taken into account and set in the
metering function. This data includes:
• Primary voltage of the voltage
transformer (factory setting: 480V)
• Secondary voltage of the voltage
transformer (factory setting: 120V)
• Connection type on the primary
side (factory setting: wye)
The following tools and functions are
available if the parameters have to be
changed:
• BDA/BDA Plus
• ETU776 display
• Data Set 129 via Profibus
secondary
primary
V 1
V 2
V 3
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