Substations are usually easily identified because they are surrounded by a fence. Typically gray in color, substations are used to either step up or step down electricity. Electricity converts from transmission to distribution in a power substation. Power must be stepped-down to be useful in a home or business, which can happen in many phases. Substation transformers can also step power up to a higher voltage allowing it to travel farther. As an integral part of the electrical system, here are some things to know about power substation transformers.
Application - The application in which a substation will be used is one of the most important things to know as it affects many aspects of the build. Depending on whether the transformer will be used for a Generator Step-up (GSU), for a furnace, to run motors, or for your standard step-down application, all play a role in how the transformer is designed to ensure that you will get the most life out of your unit. T&R Electric's experienced sales staff, and team of engineers, will walk through your needs with you, discuss how you plan to use the transformer, and together we'll make sure you have the correct unit for your application.
Protection Devices for Substations
Oftentimes there are several different types of protection devices and schemes in place within a substation. Some aren't even attached to the transformer itself. A couple of the more common protective devices and schemes are surge arresters and differential protection. Arresters are connected to the conductor before it enters the substation; the arrester is also connected to ground. It works by diverting the energy from an over-voltage transient to the ground, thereby avoiding the transformer, should a surge occur.
Differential protection, on the other hand, works on the principal of comparison by using relays that operate when the phase difference of two or more electrical quantities deviates from (exceeds) a predetermined value. This type of scheme often requires the use of current transformers (CT's) for monitoring. In either case, T&R can help you outfit your transformer to fit your protective needs.
Base Load and Max Load
Substation transformers can be designed and constructed to handle a larger load during times when an increased demand is present without exceeding certain temperature rises. A transformer generally has a "base" KVA rating (capacity rating), but in addition, it can be equipped with additional cooling means, both within the windings themselves as well as external cooling, to allow for a larger capacity to be achieved. For example, a 10000KVA transformer (base) with a 55C rise can be built to have ratings of 10000/11200/12500/14000 KVA; 10000 and 12500 are at 55C rise while 11200 and 14000 are at 65C rise. The 10000 and 11200 KVA ratings are achieved by simply accounting for a difference in temperature rise during the winding phase.
The 12500 and 14000 KVA ratings also take temperature rise into account, but in addition, they include forced air cooling. Forced air cooling is achieved by adding external cooling fans to help cool the transformer oil and stay within the defined temperature rise limits. If necessary, additional cooling radiators can also be added to the transformer tank to aid in circulation of the oil. It is important to note that the transformer must be specifically designed to handle increased demand, as simply adding more cooling means is not enough. In other words, if you are anticipating future demand increases, it is always best to let us know ahead of time, so we can get you exactly what you need!
Switching or Regulating Voltage
LTC - A Load-Tap Changer ("LTC") is an accessory that allows the substation to "switch" or "regulate" voltage while under load (i.e. the substation transformer does not have to be de-energized to switch voltages). LTC's are an integral part of many electrical systems and, similar to regulators, work on the make-before-break principal. With this type of accessory there are many variations of components and features available to choose from allowing the customer flexibility.
T&R Electric can assist you in your LTC requirements, and help determine what will work best for your application. It is also worth noting that since LTC's work differently than your typical de-energized tap changer, the oil test results, particularly the Dissolved Gas Analysis (DGA), of a substation with a LTC may differ from those of a unit without a LTC. T&R Electric also has a full service lab, with oil testing, and the professionals on hand to help you understand your oil samples.
What Size Substation Do I Need?
One of the most common questions we get asked is if T&R Electric can provide a substation transformer that will fit the current set-up. The answer is yes. Whether you have a top/top, top/side, or side/side bushing configuration will make a difference on how the wires are connecting to the substation, and will affect your space configuration. In addition, if you know the size of the pad that your substation transformer sits on, what the current dimensions are, and if there are any size restrictions, we can ensure that your reconditioned or rewound transformer will fit.
With our newly expanded substation shop T&R Electric has over 40,000 square feet dedicated to rewinding and reconditioning substation transformers. From 5 MVA up to 30 MVA, let our experienced sales staff and engineering team work with you to build a substation that meets your exact needs. Call us today at 800-843-7994 or visit us online at www.t-r.com.
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Pad Mount Transformer
Pad Mount Transformer or Pad-Mounted Transformer, it doesn't matter what
you call it because they both mean the same thing. It's a tamper-proof transformer
that sits on a concrete pad. Pad mount transformers distribute electrical power
for various applications. Here are five important things to know about a pad
When it Comes to Pad Mount Transformers Think "Inside" the Box
All of the connections for a pad mount transformer reside within a steel
cabinet. This is important because it allows the units to be installed in areas
without a fence. You can find a pad mount transformer in a backyard, at a major
shopping center, or at the ballfield. Each pad mount transformer has a tamper-proof
cabinet that houses the cables for both the high and low voltage connections. In
most applications, the high voltage and low voltage cables enter the cabinet
from underneath the transformer. For continued safety, monitor these
transformers every so often.
Most Pad Mount Transformers are Full of It - Oil That Is
The interior of a pad mount transformer contains a core and coils inside
of a steel tank filled with mineral oil. While mineral oil is the most common
liquid inside a transformer, silicone, FR-3, and other substances can be used.
The purpose of the fluid is to cool the transformer and allow it to operate
Pad Mount Transformers are Key (Superstars) to the Power Distribution System.
Pad mount transformers work in association with underground power lines.
These transformers are strategically located at service drops, which is where
transformers "step down" the high voltages supplied by utilities and electric
companies, into a lower voltage able to supply electricity to customers' homes
and businesses. The size of the transformer will determine how much power is
supplied for the application, which could be a single house/business, or an
Pad Mount Transformers are Not One-Size-Fits-All
T&R Electric can provide new or reconditioned pad mount
transformers. The power ratings, voltages, and cabinet sizes can be custom
built for a variety of specifications and applications. The power ratings can
be as low as 1 KVA in a single phase pad mount, and T&R Electric has built
custom pad mounts up to 10,000 KVA in three phase units. They often include
fuses, switches, and gauges that are all built right into the transformer, and
are customized to whatever the end-user needs.
A Station Type Transformer is Different than a Pad Mount - A Horse of a
Different Color The confusion between a station type transformer and a pad mount
transformer is understandable. After all, a station type transformer often sits
on a concrete pad, and the liquid filled steel tank encloses its core and coils.
Unlike a pad mount, however, a station does not typically have all of its connections
enclosed in a cabinet. A lot of times, the high voltage connections are outside
the station. For safety reasons, it is usually inside a fenced area. But the
easiest way to tell the difference between a station and a pad mount is by
color. Most station type transformers are some shade of gray, while pad mount
transformers are predominantly green (unless you live in the south where the
landscape lends itself better to a desert tan color). However, the best rule of
thumb is, when in doubt - don't touch!
T&R Electric Supply Co., Inc. is an industry leader that supplies all
types of transformers and other electrical components to municipalities, REA's,
investor-owned utilities, commercial and industrial customers. We also sell a
wide variety of electrical supplies for various types of distribution systems.
T&R offers a wide range of both new and reconditioned pad mount
transformers, which can be either single phase or three phase. Call us today
and let our experienced salespeople answer your questions on what will work
best for your specific application. Call 1-800-843-7994
inside the US or 1-605-534-3555 outside the US. You can also visit us online at
The Benefits of Purchasing Remanufactured
There are many
benefits to purchasing remanufactured transformers. Reduced down time. Less
environmental impact. And cost savings. Whether you are a utility, commercial
property, or industrial complex, remanufactured transformers are a safe,
economical option for your electrical requirements. T&R Electric Supply
Company, Inc. is the largest supplier of remanufactured transformers in the
United States. Consider these benefits as you examine your transformer needs.
Remanufactured is restored to like-new
Pad mount transformers, pole mount transformers, or substation
transformers can all be remanufactured, to like-new condition. This means they
are not only operational, but completely refinished to appear brand new. Our remanufacturing
capabilities include testing, evaluation, diagnosis, disassembly, and coil
T&R Electric Supply Company, Inc. has decades of experience in
remanufacturing all dimensions, voltages, and types of transformers. Single phase
or three phase, every remanufactured transformer is cleaned, inspected, and
thoroughly tested to industry standards. This intense process ensures your remanufactured
transformer performs exactly as required, and allows T&R Electric Supply
Company, Inc. to offer a three year warranty.
Remanufacturing usually means reduced
Of course you've heard the saying, "they don't make them like they
used to." Many older transformers were built very conservatively. This means
they have a greater capacity to be modified. Often times, there is not this
option with newly manufactured transformers. Remanufacturing is typically faster,
and is often 20-30% less expensive than new transformers.
A remanufactured transformer can greatly reduce your repair cost. It
can also reduce any required repair time. Because T&R Electric Supply
Company, Inc. has been in the transformer business since 1961, we are
well-stocked with several different types of electrical equipment. This means
we can expedite transformer orders with shorter lead times, and typically less
expense, than new.
Remanufactured is better for the
When you purchase a remanufactured transformer, you are keeping
various electrical components and oil in circulation . Why get rid of something
valuable that can be put back to work for good use?
With a remanufactured transformer from T&R Electric Supply
Company, Inc., you do not have to sacrifice safety, operation, or environmental
impact. Our transformers are not only built from existing inventory, they are
highly efficient. They are a great option for reliable electricity that does
not add to environmental waste. We take great pride in what we remanufacture
and how we reuse our materials.
T&R Electric Supply Company, Inc. has decades of experience in pad
mount, pole mount, substation, dry and oil-filled transformers and components.
To learn more about the benefits of remanufactured transformers, contact
T&R Electric Supply Company, Inc. to see how our transformers can best
be put to work for you.
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Constant Current Defined
T&R Electrical Supply Company Incorporated is in
the business of electricity. In our daily lives, we may take electricity for
granted. But in business, understanding all of its properties is crucial to
success and safety. Today we're discussing the difference between constant
current and constant voltage with Kent Miller, a registered professional
engineer that's been working with T&R for over 40 years.
Kent graduated from the University of Arkansas in
1960 and was inducted into the Arkansas Academy of Electrical Engineering in
1981. Kent was a charter member of the Institute of Electrical and Electronics
Engineers (IEEE), and has been a senior member since 1983. You could say he's
an expert in the industry.
Constant Current versus Constant
"In general, the difference between the
constant current and constant voltage is based on the whether the voltage or
current varies across the load," Kent explains. A constant current system
fluctuates the voltage to maintain a constant flow of energy. A driver circuit
is used as a current regulator when a component has a constant current. It
contains a feedback loop to adjust the current to hold a set value. Usually
there is some sort of voltage limiter circuit to keep the voltage below a fixed
value. Applications for a constant current include: LED's, florescent lamps,
shielded metal arc welding, and gas tungsten arc welding.
By contrast, constant voltage contains
a feedback loop to adjust voltage to hold a set value. Usually it also has some
sort of current limiter circuit, or a fuse to protect against too much current
being drawn. It provides the ability to fluctuate output current while
maintaining a set voltage, for example in welding. Constant voltage reduces
weld 'splash' and is often used to weld rounded parts.
Currents, Voltage and Transformers
In the case of T&R Electrical
Supply, let's talk about current in our transformers. "The constant current transformer, or
regulator, supplies the same current from a dead short to the maximum voltage
it can supply," said Miller. "It is normally used for supplying current to
series streetlights in downtown areas where constant current is desired.
However, several years ago most cities have retired replaced these lights with 120,
240, or 277 volt bulbs instead."
On the other hand, constant voltage
transformers are used in hospitals today, for x-ray machines, where voltage
fluctuations cannot be tolerated. Another application would be most utility
companies, who use voltage regulators. Although these are not actually
"constant voltage" transformers, they can regulate the output voltage to
approximately one to two percent of input voltage.
T&R Electric Supply Company is a
dependable supplier of transformers and other high voltage electrical apparatus
to municipalities, REA's, investor-owned utilities, commercial and industrial
customers. For more information, call 1(800)843-7994 inside the US and 1(605)534-3555, and let one of our experienced salespeople help you today!