With today’s rapidly changing technologies and electrical environments,
many "side effects" are created. Harmonics are one of the most
potentially troublesome and unpredictable problems affecting the smooth
operation of today’s modern facilities. Harmonics is a term used to
describe distortion in an electrical distribution system and can be applied
to both voltage and current.
How to Find Out if Your Business is
Affected by Harmonics:
There are a number of steps that can be taken to confirm the presence of
harmonics in the electrical system:
As a first step, tour the facility to determine the types of equipment
that are connected to low voltage systems. If this inventory includes
adjustable speed drives for motors, solid state lighting and any
equipment using switching power supplies such as computers, fax
machines and most other modern office equipment, or electronic ballasts,
harmonics are likely present.
the low-voltage power transformers that feed these non-linear loads and
check for excessive heating. Remember that the harmonics will increase
the transformers’ losses and cause them to overheat at loads below
Third order, zero sequence harmonic currents may also result in the
overloading of the transformers' neutral terminals. Neutral currents may
exceed phase currents under these harmonic conditions which will also
create excessive heat.
Using a "True-RMS" meter, measure the phase and neutral
currents and phase to neutral voltage at the low voltage power
transformers’ secondary terminal. Again, under zero sequence harmonic
conditions, the neutral current will exceed the vector addition of the
three phase currents.
Repeat step 3 with an "Average Responding" meter. Since this
type of meter is only accurate under pure sine wave conditions, any
distortion of the wave form will cause the average responding meter to
read lower. By dividing the result of the "Average Reading" to
the "True-RMS" reading, one may obtain an "A/R"
Ratio. A Ratio of 1 would indicate little or no harmonics while a 0.5
ratio would indicate a significant amount of harmonics.
In order to develop an engineered solution to this problem, it is
necessary to measure the harmonics with a Harmonics Analyzer. This is the
unit we at NRG, Inc. utilize in our Harmonics Testing
Service. This instrument provides detailed information on the spectrum
of harmonic currents and voltages including:
Total and individual harmonic distortion values.
Fundamental and individual harmonic RMS voltage and currents.
Power flow and phase angle for each harmonic.
This type of testing should be performed by an experienced person
familiar with the use of the type of equipment. The results of the testing
is what is used to determine the best possible solution to the problem.
accuracy of the test results are critical to the success of the project.
As with any mitigation technique, a detailed system study must be
undertaken in order to predict a result. Moreover, the misapplication of any
device intended to correct any electrical problem can have serious safety
implications. There is, in fact, no "off-the-shelf" solution to
Northeast Resource Group, Inc. is an experienced team of power quality
experts. Advanced software as well as advanced testing equipment provided by
NRG Inc. is used to analyze the power system at all frequencies to
optimize the application of various types of harmonic mitigation devices.
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