Production oil transformers
Construction criteria
Magnetic circuit
Windings
Box
Painting
Magnetic circuit
The cores are constructed of cold-rolled sheets grain oriented low value of specific losses. Are calculated to obtain a minimum residual flow, reduced inrush current and low noise level. The insulation between the laminations is obtained with carlyte, an inorganic oxide absolutely insensitive to high temperatures. The material, being of high quality is carefully manipulated and assembled so as to minimize the air gaps. The extreme care assembly and subsequent pressing of the core in addition to ensuring the uniformity of the structures during transport and operation, ensure a minimum rate of vibration, and hence a strong reduction of the noise level.
Windings
They are made of aluminium conductors / copper electrolyte with high conductivity and isolated in pure cellulose paper. The types are normally constructed in layers, propeller, in foil.
For medium voltages are adopted types in layers designed and constructed so as to ensure a uniform distribution of the stresses of atmospheric origin or plant.
For low voltages are adopted in propeller or foil types and their construction is such as to ensure excellent resistance to stress short-circuit.
The axial channels between the layers of the windings ensure optimum and uniform oil circulation for cooling. The maximum symmetry of any power adjustment avoids dangerous failure of ampere-turns eliminating annoying electrodynamic forces in case of short circuit.
Box
The box is made with steel sheets of suitable thickness to mechanical stress. The fund is equipped with skids or wheels. The lid is secured to the case with bolts placed around the entire perimeter. The seal of the lid and the box is obtained by a seal-oil and corrosion caused bye the weather. The cooling is done through radiators on the sides of the case.
Painting
All metal parts are treated and painted so as not to be erode over time by weathering with paint approved Enel.
Insulating liquid cooling
Testing
Standard version
Accessories on request
Insulating liquid cooling
Insulating oils normally used are :
- Mineral oil obtained from the fractional distillation of crude oil. Features of this type of liquid is to not contain inorganic acids, alkali, sulphur dissolved, asphaltic products, vegetable or animal oils or other impurities. Type of oil A.A. IEC standard.
- Silicon oil. This type of oil in addition to having excellent insulating power, has the special feature to extinguish and the spread off lame.
- Oil Midel 7031
Testing
Each transformer is subject to acceptance tests established by the CEI and IEC and tested in the our testing room, where they performed the following tests :
- Measurement of the transformation rations
- Check polarity and angular displacement
- Insulation tests with alternating voltage
- Measurement of the chemical resistance of all windings accessible
- Measurement of no-load losses and no-load current
- Measurement of load losses and short-circuit voltage
Standard version
- Insulators porcelain MT
- Porcelain insulators BT and neutral
- Switch off the MT side operated with voltage transformer
- Filler cap for transformers with conservator – pressure relief valve for transformer hermetic filling
- Sliding wheels
- Oil drain valve
- Sockets ground steel
- Nameplate
Accessories on request
- Dial thermometer with two electrical contacts
- Relais Buchholz vertical (up to 1250 kva ) or horizontal (more than 1250 kva) with two electrical contacts
- DGPT 2 for hermetic transformers
- Transformers 60 Hz frequency
- Dumpsters MT-BT
- Special needs of the customer
Quality control and certification
The entire production of Eletrafo is based on the application of all phases of the process, quality system according to
– UNI EN ISO 9001 –
– ISO 14001:2015 Environmental Management System
Collaudi - Norme di riferimento
Durante le varie fasi del processo di produzione, vengono effettuate le prove che fanno riferimento alle istruzioni operative sistema qualità. Tutti i trasformatori vengono collaudati secondo le norme CEI-IEC con prove di routine eseguite nella nostra sala prove. Le prove di tipo sono eseguibili presso un laboratorio esterno (ad esempio, CESI – Milano), con costo aggiuntivo per ogni test.
I nostri trasformatorisono prodotti in conformità alle seguenti normative :
- Trasformatori in olio minerale : CEI 14.4 – IEC 60076 1/12 EN 50464-1
- Trasformatori a secco in aria : CEI 14.8 – IEC 726
- Trasformatori inglobati in resina : CEI 14.8 – HD 464 – IEC 60076 – 11