Range TTR
Technical parameters
Output range: Rated voltage: Tapping on primary: Secondary voltage: Frequency: Vector group: Cooling: Winding conductor material: Isolation class: Protection degree transformer: Max. average temperature rise: |
50 ÷ 3 150 kVA up to 52 kV ±2x2,5 % (or other) 400 V (or other) 50 Hz Dyn1 AN (AF) Cu or Al F IP00 100/100 K Parameters and drawings |
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Main features
TTR transformers are three-phase dry transforms with high-voltage winding, cast in epoxy resin in a vacuum and they represent an alternative to traditional oil-immersed transformers. SEA manufactures and develops these transformers since 1975 and, due to their used design solution, unified components, and modern technology; they are among the leading European manufacturers in this field. TTR transformers are designed to satisfy the demands of all customers from standard up to special applications.
Manufacturing technology
Magnetic core
The core is composed of grain-oriented magnetic sheets featuring high permeability and reduced specific losses, separated by inorganic insulation (carlite). The special cutting and assembly of the core allow for “STEP-LAP” joints which reduce noise as well as losses and the no load current. The magnetic sheets are pressed by galvanized core clamps. The core is insulated and varnished in an F temperature class.
Low voltage windings
The secondary coil consists of an electrolytic aluminum foil conductor interwound with an insulating film in pre-preg class “F”, then subjected to the oven drying process. The outlet terminals are aluminum bus bars welded in an inert atmosphere and firmly locked to the frame with spacer insulators.
This type of structure guarantees:
- high resistance to moisture and industrial aggressive atmospheres
- great dielectric sturdiness
- excellent mechanical performances versus short-circuit stresses
Copper windings or windings as per customer specifications are available on request.
Medium voltage windings
High voltage winding is carried out by automatic machines and consists of a set of electrolytic aluminum tape coils. The insulation between turns is obtained through a polyester film. The entire coil is framed by a glass fiber net, dried in depth and subsequently vacuum incorporated with a class F epoxy resin mixed with quartz and trihydrated alumina. This assures excellent mechanic sturdiness and compliance with classes C1 and C2 of the IEC rules.
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Based on the manufacturer’s 30 years’ experience and the implementation of automatic devices (which control and record all the critical parameters of the process) we can guarantee extremely reduced partial discharges (about 5 pC), an essential requirement for the manufacture of quality, reliable and long-lasting coils. The adjustment links (generally ±2x2.5%) are obtained directly at the center of the coil.
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Final assembly
The final assembly is carried out with care and accuracy. Assembly accuracy is fundamental to guarantee the optimal performance of the transformer when subjected to the electrodynamic stresses caused by short circuits. The Low Voltage is mounted on the core and held in place by special glass fiber spacers. The LV connection bars are locked to one other and to the core clamps by fiber glass insulators. The Medium Voltage winding is braced by spacers which allow small axial expansions when the load current flows through the winding.
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Testing
Every transformer is tested in our test room with routine tests in compliance with IEC60076-11, i.e.:
- measurement of winding resistance
- measurement of the transformation ratio and control of the connection group
- measurement of losses and short circuit voltage
- measurement of the no load losses and no load current
- checking the insulation with applied voltage
- checking the insulation with induced voltage
- measurement of partial discharges
At the customer’s request all type and special testings provided for by the rules may be carried out:
- heat run test with simulated load method
- heat run test with opposition method
- impulse withstand test with full and chopped wave
- measurement of noise level
- measurement of the contents of harmonics in no load current
- measurement of homopolar impedance
- measurement of winding capacitance
- dynamic short circuit withstand test (to be carried out by an authorized external lab)
- fire resistance test and checking of response to climate classes (to be carried out by an authorized external lab)
- other special tests to be agreed upon periodically with the customer (electromagnetic emissions, thermal shocks…)
Archive of type tests
SEA has a large archive of type and special tests carried out on many resin transformers delivered to customers worldwide. The archive is available at all times for our customers to consult.
Installation
Room temperature and load conditions
The resin transformers from the TTR series have been designed to supply nominal power in a regular distribution network, the conditions of which are defined by IEC 60076-11 Standards. Heights over 1000 meters, room temperatures higher than 40 °C or specific network or load conditions (presence of overvoltages, harmonics, overloads…) place dielectric, mechanic or thermal stress on the transformer which has to be considered during the design process in order not to compromise its reliability and life.
Room dimensions
Many components of the resin transformer may be easily touchable when the machine is operating. The same MV coils insulated with epoxide resin and the connections for closing the triangle circuit, generally insulated by a heat shrinkage tube, must be considered as “live parts”, thus the machine has to be properly segregated.
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The cell should allow for the proper exchange of air (at least 4.5 m3/minute of air for every kW of loss). The distance of the walls from the live parts should comply with the current local rules and in any case be shorter than those indicated in table 1.
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Tab 1
Protection enclosure
The transformer is generally delivered in a IP00 protection degree. At the customer’s request the transformer may be supplied with a cabinet for indoor installations featuring a protection degree in compliance with the customer’s specifications. In this case the cabinet itself protects the transformer from accidental contact. The installation room should in any case feature dimensions and distances as to ensure the proper exchange of air (there should be approximately 500 mm distance between the cabinet wall and the room wall, to allow for both proper air circulation and the regular inspection/maintenance of the transformers).
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Connections
The type TTR dry transformers with standard operation provide for LV bus bars designed for top-side connections and bottom-side MV line connections. Connection instructions common practice for the installation technicians. We recommend properly supporting and connecting the bus bar and the connection cables so that their weight and most of all electrodynamic stresses due to a possible short circuit do not influence the transformer’s performance.
Special attention should also be given to the MV cable: the outermost insulation of cables shall be considered at ground potential, therefore must be kept at a certain distance from the transformer live parts in the same way as for the other accessories, in compliance with table 2.
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Tab 2
Main features
TTR Transformers are three-phase dry transformers with englobed MV resin windings, which represent a valid alternative to the traditional oil-immersed transformers. SEA has been designing and producing this type of transformers since 1975, making itself one of the leading firms in the sector thanks to its construction solutions adopted, unification of details and to modern technologically advanced production facilities. SEA TTR transformers have been designed to satisfy our customers’ needs, from single users to large industrial groups, assuring:
- Health protection and maximum safety - The materials used are auto-extinguishing and do not release toxic gases in case of fire.
- Installation economy - They do not require the construction of an oil-collection tank.
- Operation economy - They minimize maintenance and extend the transformer’s lifetime.
- Versatility and performance - They can support overloads and perturbations which can be found in every installation.
- Maximum reliability - Control and quality are guaranteed at every single stage of the design and manufacturing process.
The absence of inflammable liquids facilitates the plant engineer’s work, who can carry on the project more freely. This advantage is especially appreciated for those installations where operational safety is fundamental, for instance in hospitals, public premises, airports, subway lines, mines, oil platforms, nuclear plants, ships, etc…
Standards references
SEA dry transformers comply with the IEC 60076-11 standards.
The construction based on other rules and/or standards may in any case be required and verified by our engineering and commercial department.
Range
The standard catalogue covers up to 3150 kVA and 36 kV. Our design and construction capacity can satisfy the most diverse of needs (autotransformers, applications for converters, for traction, for testing rooms, etc…), with powers up to 25MVA.
Standard accessories
- N. 4 bi-directional wheels
- N. 2 grounding terminals
- N. 1 identification plate
- N. 2 or 4 lifting lugs (according to rated power)
- N. 4 connections for haulage
- Tapping terminal board on MV side
- Threaded pins provided with bolt for MV terminal connection
Accessories on request
- Twin-contact dial thermometer
- PT 100 thermoresistances
- PT100 electronic unit
- PTC thermoprobes
- PTC relays
- Elastimold type plug connections MV side
- Anti-vibration supports
- Protective cover for the tapping links
- Auxiliary service terminal board, protected type
- Set of electrofans for forced air (AF) cooling
- Electrostatic screen between primary and secondary
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