Converter transformers hermetically sealed with expandable radiators

Country: Bolivia
Region: 250 km South-West of Santa Cruz Province in the foothills of Andes Cordilleras 
Type of Project: Gas development field

A well-known worldwide Oil Company started the exploration of gas in Bolivia in 1996 managing some blocks from north-south along the line of the top of the central mountain range near the town of Camiri in Bolivia.
The Company will develop the first gas processing train of three production wells with a nominal capacity of 6.9 MSm3/d.
From technical point of view, this project requires complex technologies due to high pressure and temperatures and also because the natural gas is trapped 6,000 meters dept underground of Andes Mountains Range: that is calling for special drilling and production techniques.

SEA was chosen to share its expertise in this important  development project as partner for the supply of the converter transformers.
With these two units SEA confirm its strength in Oil&Gas segment application with the relevant operational benefits such as lower emissions, reliability and installation cost savings that can offer to their Customers.

Power converter transformer, oil immersed hermetically sealed / completely filled tank design with expandable radiators
Power rating: 6.2 MVA
Primary Voltage:  6.6 kV
Secondary Voltages:  4 x 925 V with 12 secondary terminals
Type of cooling: ONAN
Protection degree: IP55
Altitude of installation: upper than 1000 m.a.s.l
Special painting for onshore application C5-Ma

Quantity: 2 pcs

The final application is for variable speed drive system (static frequency converter type VSI), each secondary directly connected to 6 pulses diode rectifier with a special harmonic spectrum to be considered.
The main characteristic of these transformers for 24 pulses studied for this particular application is that they are integral filling without the conservator but with expandable and detachable radiators.
While in the traditional transformer with conservator the variation of the oil volume which depends on the temperature is kept under control through the expansion tank commonly known as "conservator", the hermetic solution uses the radiators with a special variable volume expansion that allows to overcome the lack of such fitting.
The hermetic transformer has the absolute advantage the almost total absence of maintenance of the transformer and a life expectancy greater than those with conservator.

This innovative hermetically sealed tank design equipped with expandable radiators is a solution studied for:

- extending life time of the transformer;
- increasing of overload ability;
- reduction of costs for the devices of conservator;
- reduction of maintenance costs;
- reduction of cellulosic insulation and oil ageing;
- prevention of contact between oil and atmosphere moisture.