2011 EMC Directory & Design Guide - Interference Technology

K e e bl e r, Berge r
radiated emissions
slated for use in the new plants will provide much needed
emissions guidance and aid in the prevention of future EMI
problems.
Figure 3. Radiated electric field spectra, 10 kHz to 1 GHz, antenna
position 2 in control room (Unit 1).
3). Although these limit lines are intended to determine if
the emissions from a single piece of equipment or system
are too high, the emissions from both the ACS and the DCS
equipment do exceed these limit lines.
2) Antenna Position 2
Figure 3 illustrates the final radiated emissions trace for
electric fields taken at Antenna Position 2 from 10 kHz to
1 GHz adjacent to one of the system cabinets for the plant
control system. This trace contains the data for both the
analog control system (red trace) and the digital control
system (blue trace). From Figure 2, one can see that a few
characteristics of the analog control are that it peaks at
1.04 MHz at 99.3 dBμV/m and again at 4.55 MHz at 88.5
dBμV/m. Again, these two traces cross the NUREG 1.180
and EPRI TR-102323 equipment emissions limit lines for
high frequency radiated emissions.
While the radiated emissions in the region between 139
kHz and 2.61 MHz have dropped as a result of converting
the plant control system from analog to digital, there are
other regions (e.g., A, B, and C) that have increased in amplitude.
132 These three example areas have experienced
amplitude increases ranging from a few dB to as much as
high as over 40 dB. With the nature of radiated emissions
being cumulative with increasing digital devices in areas
such as Control Rooms, areas such as A, B, and C will
experience significant growth in amplitude more closely
approaching the plant emissions limit line (yellow line)
defined by EPRI TR-102323.
As additional digital control equipment is installed in
the Control Room, these emissions levels will grow. Moreover,
with the new advanced nuclear plants presently under
design (some under early construction), I&C engineers can
expect new concerns regarding higher emissions levels and
new EMI problems as digital I&C controls are brought on
line. This is an area that deserves careful consideration in
efforts to lower the risk of allowing an EMI problem to occur
in the fleet of advanced nuclear plants built and placed
on the grid over the next ten years. Efforts put into place
to gather emissions data for new digital I&C equipment
High-Frequency Radiated Emissions –
Electric Fields: 1 – 6 GHz
1) Antenna Position 1
Figure 4 illustrates the radiated emissions trace for electric
fields taken at Antenna Position 1 from 1 to 6 GHz adjacent
to one of the system cabinets for the plant control system.
This trace contains the data for both the analog control
system (red and blue traces) and the digital control system
(purple trace only).
From red and blue (upper) traces, one can see that there
are no significant peaks associated with the analog control
system. However, with the digital control system there are
peaks at 1.35 GHz at 49.9 dBμV/m, 1.88 GHz at 50.5 dBμV/m,
1.92 GHz at 53.4 dBμV/m, 2.41 GHz at 76.3, 2.46 GHz at
54.4 dBμV/m, and 5.82 GHz at 60.6 dBμV/m. Some of these
spectral components are higher at Antenna Position 1 than
at Antenna Position 2.
From increases in the usage of digital equipment in other
mission-critical environments where surveys have been
carried out, it is reasonable to predict that the above components
will experience a growth in amplitude in addition
to the development of new components with faster proces-
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