Application Note

Power Quality Troubleshooting Fluke Corporation 7
Solutions
Performance Wiring vs.
Code Minimum
Any experienced PQ trouble-
shooter will tell you that the
first place to look for most prob-
lems is in the building wiring
system (including its grounding
system). Quality power depends
on quality wiring; the term the
industry uses is performance
wiring (See Table 1.2). The ba-
sic intent of performance wiring
is to maintain or restore L-N
voltage to the load. There is a
distinction between “perfor-
mance wiring” and “code mini-
mum” wiring. The NEC sets the
absolute minimum requirements
for a wiring job and is primarily
concerned with fire prevention
and personnel safety. The NEC
should, of course, never be vio-
lated, but it is also important to
understand that the Code’s ob-
jective is not to establish stan-
dards to achieve power quality.
However, many facilities are
finding that it pays to take the
extra step and install or even
retrofit a performance wiring
job. As one veteran said, “If
every building were perfor-
mance wired, I’d be out of
business. . . But there’s no fear
of that happening.”
Power conditioning
There are also situations where
receptacle-installed power con-
ditioning devices are a good so-
lution, either as a complement
to the wiring changes or as an
economically viable alternative
to some wiring changes.
Recording at the
receptacle outlet
By monitoring voltage events at
the receptacle, you can see ex-
actly the same voltage that the
sensitive load sees.
The VR101 is plugged into
an outlet, and can record up
to 4000 events, including:
•
Voltage sags and swells(rms)
•
Outages
•
Transients (L-N and N-G)
with peak values
•
Frequency deviation
Events are identified by type,
real-time stamp, and duration.
VR101S operation
Set up
Use EventView software to
configure the device. The unit
comes with default thresholds,
but users can enter new thresh-
olds. An optical wand, supplied
with the software, transfers
new configurations to the VR101.
Plug in
The VR101 is left on-site for as
long as needed. No computer
connection is necessary. It
draws power from the line and
in the event of outages, a built-
in battery saves data.
Download
The VR101 is taken to the
computer. The optical wand
retrieves its data.
Analyze
Events are displayed in spread-
sheet format in EventView
software. Charts, graphs and
waveform graphics are also
provided for report generation.
Table 1.2 Suggestions for performance wiring of branch circuits.
Recommendation Reason
Check for loose connections. It’s easy to overlook the obvious.
Eliminate shared neutrals. In new Minimize load interaction and source
installations, pull individual neutrals impedance.
for each branch circuit.
Limit the number of receptacles per Minimize loading and load interaction.
branch circuit to three.
Limit length of 120V branch circuits Minimize source impedance.
to 50 ft. (15m).
Install dedicated branch circuits for all Keep victim loads and culprit loads separated.
laser printers and copy machines. Dedicated Conduit prevents coupling between circuits.
circuits should be run in their own conduit.
Install a green wire ground (don’t just Maintain a continuous, low impedance
depend on the conduit connection). ground.
Label all panels, circuit breakers and Strictly speaking, this won’t improve power
receptacles. quality, but it will sure make life easier for
the troubleshooter and the installer.
50 ft
15m
Laser
Printer
Copier
200 ft
60m
Figure 1.5 Performance wiring.