American Oil and Gas Reporter - June 2019 - 77

SpecialReport: Artificial Lift Technology

Utility Incentives Promote VFD Usage
By Dan Patel
ATLANTA-Utilities in New Mexico
have developed economic incentives to
encourage oil and gas producers to install
variable frequency drive technology to
prevent power surges at the transformer
level of utility lines. Since a sudden
power surge can damage a utility's transformers and create power outages for
other customers on the local grid, it is to
a utility's advantage to incentivize its oil
and gas industry customers to adopt VFD
technology to prevent the problem from
occurring.
This creates a win-win situation all
the way. The producer saves on power
costs and has more efficient control and
data for any given production scenario,
and the utility has a safeguard against
surge-related service disruptions as new
wells are connected to the grid. With activity soaring in the western part of the
Permian Basin in Southeast New Mexico,
the producing well count has doubled
over the past three years and tripled over
the past six years, adding new demand
on the local electric grid to power pumps
and other production equipment.
Amtech Drives has installed numerous
resistorless VFD systems to control pump
jacks in the New Mexico portion of the
Permian Basin. The VFD system allows
customers to qualify for and receive
rebates from the local electric utility,
Xcel Energy. VFDs reduce power demand
and improve efficiency. The right system
will allow the sucker rod to run at the
optimal speed to match the rate at which
the formation produces oil.
Thanks to a proprietary algorithm,
starting current is limited by 120~150
percent of rated current and running
current is 100 percent or below the rated
current. Limiting the starting current prevents a high inrush of current through
the utility's transformer, which in turn,
prevents unnecessary failures and power
outages, and the size of transformer can
be reduced.
The VFD system comes equipped with
a line reactor and surge suppressor that
handle power surges and spikes at remote
producing sites. The VFDs provide a
much smoother start than across-the-line

systems that turn the pump on and off
every few hours. By eliminating the mechanical jerking associated with abrupt
starts, the technology reduces wear and
tear on pumps and extends service life.
The units also interface directly with
most pump-off controllers, including those
provided by major pump manufacturers.
Reusing Energy
By integrating the VFD package with
advanced pump jack control technology,
the units can handle regenerative energy
without a braking power resistor/braking
unit. This prevents wasting electrical energy and allows it to be utilized in the
pump's operation when it is needed. The
idea behind the technology is to redirect
and reuse energy that is wasted in traditional systems.
It is difficult to balance a pump jack
perfectly, so there is a part of each stroke
where the weight of the rods causes them
to fall more quickly than necessary, or
the counterweight of the surface equipment
pulls the rods up at a faster rate than required. While this is occurring, the motor
is generating excess energy. A traditional
system sends that energy to brake resistors,
which dissipate it as heat. That works,
but the resistors only last a year or two,
especially in areas such as Southeast New
Mexico and West Texas where ambient
temperatures are high.
Rather than wasting this energy, the
VFD system saves it and gives it back to
the motor when needed. How much that
impacts energy costs will vary based on
the specifics of the application and the
agreement the producer has with the power
company, but assuming an electricity cost
of $0.04-$0.07 per kilowatt hour, it is
usually enough to save $7,000-$10,000 a
year. That means the VFD will pay for

itself in a year, then put that savings in the
producer's pocket every year thereafter.
In addition, Amtech can provide harmonic mitigation to comply with the IEEE
Standards Association's recommended practices and requirements for harmonic control
in electric power systems (IEEE 519, 2014).
A harmonic is a frequency that is an integer
multiple of the fundamental frequency generated by nonlinear loads. Nonlinear loads
use short pulses of current, thereby generating harmonics in power distribution lines.
Normally, a standard six-pulse rectifier
base VFD generates more than 75 percent
current harmonics. It is more harmful
where multiple VFDs are on the same line.
Higher harmonics distortion can increase
transformer eddy current loss, increase
temperature and result in failures in a short
time. The VFD package helps reduce harmonics effects on power transformers and
avoid contingency failures.
The VFD package has the capacity to
convert one phase to three phases in
remote areas where single phase is all
that is available. Instead of a traditional
phase convertor or diesel generator, a
VFD is an efficient and effective solution
for oil and gas production operations. In
fact, remote VFD monitoring services
are even available to assist the producer
in reducing downtime and enhancing system efficiency, and ultimately, even increasing safety ratios.
❒
DAN PATEL is chief executive officer
of Atlanta-based Amtech Drives, which
manufactures power and torque modulation, automation, power quality
and industrial electronics products,
including variable frequency drives
and soft starter solutions for oil and
gas production equipment.

Editor's note: Rebates and other incentives for installing variable frequency
drives are available in numerous states
and for many types of commercial and
industrial applications, including oil and
gas production operations. Oil and gas
companies can contact their local electric
utilities to inquire about incentives available in specific service areas.
JUNE 2019 77

American Oil and Gas Reporter - June 2019

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