Case Studies

2 Fluke Corporation Performing power quality studies and troubleshooting loads
first, and he recommended its
replacement. Company officials,
however, wanted proof that
changing out this second drive
would be the final step in
protecting the utility’s trans-
former. During the first upgrade,
interfacing the new drive and
its controller with the existing
die cutter had been a tech-
nological challenge, and the
whole project was quite costly.
The company did not want to
repeat the same process with-
out being sure that the upgrade
would accomplish what it was
intended to.
Purchasing a power
logger
While the initial tests, the first
upgrade, and subsequent tests
pinpointing the second machine
took place, McArthur looked for
a power logger more suited to
this kind of work. He wanted
an affordable instrument that
would provide the baseline
findings he was looking for and
provide concise reports on only
Initially, the consultant iden-
tified one drive as a source
of wayward dc current. It
was a die cutter’s drive that
was reflecting a considerable
amount of the second and
fourth harmonics back into the
distribution panel and from
there into the transformer.
These even harmonics indicate
the presence of dc. Therefore,
at McArthur’s suggestion, plant
personnel replaced the more-
than-20-years-old offending
drive with a more modern unit.
“We thought that would take
care of the issue,” McArthur
says, “but when we started
looking at the main service
scan, we saw that we still had
just about the same amplitude
for dc current, indicated by the
second and fourth harmonics.
So, we had to isolate another
machine as the source of the
additional dc.”
Using the instruments at his
disposal, McArthur pinpointed
the culprit: another die cutter
with a drive similar to the
the parameters that interested
him. His search led him to the
Fluke 1735 Power Logger, an
affordable instrument developed
for consultants like him as well
as plant electricians and electri-
cal installers, all of whom have
occasion to investigate and
correct disturbances in power
distribution systems and who
would benefit from owning,
rather than renting, a logger.
Not only was the recently
introduced Fluke 1735 capable
of detecting and displaying the
harmonics that were creat-
ing havoc in the paperboard
company’s electrical distribu-
tion system, McArthur saw
unlimited potential for it in his
commissioning work as well as
in load studies and energy-use
assessments. In addition, the
instrument could capture volt-
age events—sags, spikes and
interruptions.
In McArthur’s own words,
“The 1735 promised to be very
useful in harmonics environ-
ments. Using the software that
comes with the instrument, I
would be able to isolate each
harmonic if I wanted to and do
a trend plot or histogram. But
on this particular job, all I had
to be able to do was to see the
actual amplitude of the second
and fourth harmonics on the
customer’s transformer.”
Meanwhile back at
the plant
McArthur obtained a Fluke
1735 Power Logger and put
it on the main transformer at
the paperboard plant. He then
turned off the suspect die cutter
and sampled the electrical envi-
ronment. With the die cutter
not running, the second and
fourth harmonics were essen-
tially nonexistent. However,
when plant personnel turned
the machine on, the second and
fourth harmonics went from
almost zero amps to between
six and 13 amps.