IEC 60076­-11 EU 548­-14

IEC 60076­-11 EN 5054­1-1

IEC 60076­-11 ECORES

IEC 60076-­11 POLE MOUNT

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This document prescribes the main characteristics required for cast resin transformers.


All TMC equipments shall comply with the latest issues and revision or amendments of standards:

  • EN 50541-1

  • IEC 60076 – 11 dated 05/2004 Standards and other related standards.

Tolerance on the guaranteed values as from above mentioned standard.


An epoxy resin mixed with silica and tri-hydrated alumina will be used to enclose the high voltage windings. The resin will be treated in a vacuum autoclave in order to eliminate air or any other gas and to obtain the maximum degree of degasification.

This epoxy compound must be characterised by optimum dielectric and mechanical properties to be able to withstand the stresses it will undergo during the normal life-span of the transformer. The epoxy compound used presents a complete absence of hygroscopicity and is self-extinguishing. Furthermore, in order to minimize risk of cracks in case of sudden change in load or temperature, it is characterised by a coefficient of expansion whose value is very similar to that of the conductor.

Thermal insulation class is according to class F which provides for a maximum operating temperature of 140°C and it is certified by the manufacturer and supported by ageing tests.



The primary winding will be made with aluminium conducting tape interwounded with insulating film over a fibreglass support carried by a metal frame.

Both the conductor and the support must have a thermal expansion coefficient close to the epoxy resin, to ensure a mechanical strength and expansion compatibility, which is required for compliance of the product to class C2.

The support also must bind the coils in such a way as to allow handling and erection of the moulded winding without any risk of misalignment. The voltage gradients between turn and turn and also between layer and layer are dimensioned in order to have an extremely low and uniform internal dielectric stress.

Furthermore, the smooth surface of the foil ensures a superior and more homogeneous resin penetration during casting process: this ensures a partial discharges value usually below than 10 pc.

The primary winding is equipped with voltage tape changer, normally set at +/-2 x 2.5%. The insulating materials must be in thermal class F and allow a maximum value of temperature of 140°C, as allowed by the IEC standards, measured during a temperature rise test.

The epoxy compound used is self-extinguishing in compliance with class F1. Should the transformer fail, both self-extinction and the absolute absence of toxic gases is assured. The opaqueness of the flue gas is tightly controlled, and the measured values are well below the limits allowed by the safety standards in force.


The secondary winding will be manufactured using an aluminium foil conductor with the same height of the primary winding. The particular windings compactness will guarantee the resistance to the axial and radial stresses generated by short circuits. Moreover, since the turns are completely free from air pockets, the exceptional compactness of the winding also guarantees a very uniform heat dissipation.

Weldings to the LV connections will be carried out by fusion and without weld material. Conductors will be butt-welded to prevent the formation of raised weld joints, which might cause damage to the insulation between outlet terminal and turn.

A vacuum resin-impregnation process ensures total protection of the product against humidity, salinity and pollution. The coils may be exposed to even the most demanding environments, in full compliance with class E2.


The magnetic core will be manufactured by magnetic sheets with oriented grains and low losses, the surfaces will be insulated by Carlyte to reduce the no load losses due to the eddy current.

The magnetic core is manufactured using high-permeability and low-loss grain-oriented steel sheets. The insulated surface of these sheets minimises losses due to stray currents.

The core components are assembled on special workbenches in order to prevent any deformation of the individual sheets, also assuring a perfect core alignment. The joints are 45° step–lap type to minimise stray-flux losses and to prevent joint vibrations, which is the primary cause of noise.

Non-hygroscopic paint covers sheet surfaces, protects the various sheared parts against oxidation and corrosion, and further contributes to noise reduction.


Each transformer will be equipped with the following accessories:

  • Medium Voltage connections with insulator on each phase.
  • Low Voltage connection by aluminium plates treated to joint with copper bars.
  • Horizontal towing hooks and eye bolts for lifting
  • Off load tap changer ± 2×2.5%
  • Bidirectional wheels
  • Earthing terminals
  • Rating plate to IEC standards


Each transformer shall be subject to the Routine Tests according to IEC60076-11 and, if necessary, tp the relevant Type Tests.


Type Tests upon request, in compliance with all relevant international standards:

  • Heating, Impulse, Noise (in anechoic chamber)

  • Tests in the presence of clients or third certifier boards

Check Testing for further details.


TMC Transformers is ISO certified for 9001: 2015 quality standard and tests have been carried out on products at CESI laboratories for compliance with E2 environmental class, C2 climatic class and F1 fire behaviour class, according to the CEI – IEC 60076-11 standard (May 2004).

TMC Transformers complies with international regulations on safety and the environment. The environmental management system is ISO certified for 14001:2004 regulations, while the health and safety management system follows the OHSAS 18001:2007 standards.


TMC Transformers is ISO 9001, Version 2015 certified and operates in compliance to its standards in order to guarantee the best quality products to its clients.