Below are definitions relating to substation transformers, components and accessories. Please feel free to print this page for reference. If you have any questions, please e-mail us.

Condition	KVA	Phase	Voltage	Windings
Terminations	Gauges	Fan Cooling	Taps	Cooling Fluid
Surge Arresters	Accessories	Temperature Rise	Frequency	E-Mail Us

Condition New All components are new Remanufactured Transformer coils have been rewound; this may include all primary and secondary coils or primary coils only; even if secondary coils are not rewound they will carry the same warranty as the rewound primary coils; may also include new oil Reconditioned Transformer has passed all standard tests; if needed, broken or missing parts are replaced As is Transformer will be sold in its present condition without warranty; Alfa Transformer rarely sells transformers in this condition and it is usually at the request of the customer Rental Transformer condition can vary but all rental units will be in good, working condition  Return to Substation Quotation Request Page

KVA Kilovolt ampere; designates the output which a transformer can deliver at rated voltage and frequency without exceeding a specified temperature rise Return to Substation Quotation Request Page

Phase Classification of an alternating current circuit; most common phases are single-phase and three-phase; standard transformers do not have mixed phases; if a transformer has a three-phase input, it will have a three-phase output; the same is true of single-phase transformers; it is common to connect a single-phase transformer to a three-phase system and get a single-phase output Return to Substation Quotation Request Page

Voltage Primary Voltage The INPUT voltage of a transformer; this should include a numeric value and a vector designation (see below) Secondary Voltage The OUTPUT voltage of a transformer; this should include a numeric value and a vector designation (see below) Vector DELTA - A standard three-phase connection in which each phase winding is connected in series to form a closed loop; on a Delta connection of a three-phase transformer, the transformer will have three (3) bushings WYE - A standard three-phase connection in which similar ends of each phase winding are connected together at a common point which forms the electrical neutral and is often grounded; on a Wye connection of a three-phase transformer, the transformer will typically have four (4) bushings Single-phase pad mount transformers can also have vector designations to indicate how they will be connected to the primary (input) voltage source. Return to Substation Quotation Request Page

Windings The primary and secondary windings of the transformer can either be copper or aluminum, or one can be copper and the other aluminum. The industry standard, since the early 1970's, has been aluminum. For more information on copper and alumimum, see our Copper vs. Aluminum article. Return to Substation Quotation Request Page

Terminations Terminations (bushings) can be located on the cover or side of a substation transformer. Cover-mounted bushings are typically exposed to facilitate overhead feed of cables. Side-mounted bushings are typically enclosed in a throat or flange which may then be connected to a partial-height or full-height air terminal chamber (ATC) for underground feed of cables. Cover Bushings Side Bushings Throat Flange Partial-Height ATC Full-Height ATC Return to Substation Quotation Request Page

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Gauges Liquid Level Indicates the level of cooling fluid in the transformer Oil Temperature Indicates the temperature of the cooling fluid; may include a manually-resettable maximum temperature indicator as shown in the photograph Pressure/ Vacuum Indicated the pressure or vacuum of the transformer tank With Contacts When auxiliary equipment is used, such as fans, visible or audible alarms, or other similar equipment, gauges may include contacts Return to Substation Quotation Request Page

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Fan Cooling Fans can be optionally installed on many substation transformers as a means of reducing the transformers operating temperature; generally, fans are not used on transformers below 1000 KVA because it is cost-prohibitive; cooling fan packages can include fans, temperature gauge, auxiliary wiring compartment, mounting hardware, or other options Return to Substation Quotation Request Page

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Taps Tap Changer Used to adjust for low or high incoming voltage; for de-energized operation only Return to Substation Quotation Request Page

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Cooling Fluid Mineral Oil Common dielectric fluid used in transformers, circuit breakers, oil-filled switches and X-ray equipment RTEmp® A fire-resistant dielectric coolant; non-toxic and biodegradable; typically costs about 3X to 5X more than mineral oil Silicone A fire-resistant fluid; a good choice where potential fire hazards exist; typically costs about 3X more than RTEmp® Envirotemp® FR3™ A unique dielectric coolant made from seed oils; exceptionally high fire point; non-toxic, non-bioaccumulating and readily biodegradable Return to Substation Quotation Request Page

Surge Arresters Used to dissipate overvoltage surges and lightning strikes that exceed the voltage rating of the arrester; arresters come in three classes - distribution class, intermediate class and station class; they are externally mounted on a support frame or in an enclosed cabinet Return to Substation Quotation Request Page

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Accessories Pressure Relief Valve A small valve that will automatically release overpressure from a transformer tank; automatically resets when sufficient pressure is released; can be activated manually when using extreme caution and recommended safety procedures Sudden Pressure Relief Device A cover-mounted device that activates when a specified tank pressure is reached; relieves pressure much more rapidly than a pressure relief valve Drain Valve with Sampler A device used to drain oil from transformer; sampling valve allows for a lesser flow of oil for sampling purposes Return to Substation Quotation Request Page

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Temperature Rise The temperature increase over the ambient temperature due to loading; lower temperature rises are better because the transformer operates cooler than an equal, higher temperature rise transformer; standard temperature rises for oil filled transformers are 65°C and 55°C Return to Substation Quotation Request Page

Frequency The number of times an alternating current voltage will alternate from positive to negative and back again within a specified period of time; usually express in cycles per second and identified as Hertz (Hz); the Western Hemisphere primarily operates on 60 Hz systems; some 60 Hz systems exist in the Eastern Hemisphere but it is primarily 50 Hz systems Return to Substation Quotation Request Page

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