Jul 2 2008
Siemens Energy has built a power transformer with insulating liquid based on plant oil for the German utility EnBW. EnBW will be operating the transformer under real-life service conditions to study a number of aspects, including its thermal and electrical load capability in continuous operation. The transformer, which has a power rating of 40 MVA (107/21 kV), was manufactured in the Dresden transformer factory. The tank is filled with natural ester liquid based on rape seed oil and is hermetically sealed. Compared with a conventional oil-insulated transformer, the transformer from Dresden has improved fire protection properties and, because the insulating liquid is biologically degradable, could also be operated in areas subject to stringent environmental regulations.
EnBW is deploying the transformer with the alternative insulating liquid at the Teinach substation near Bad Teinach-Zavelstein in the Black Forest to investigate and document its operating behavior there under actual service conditions. For this purpose, the hermetically sealed power transformer is being kept under permanent surveillance by a monitoring system. The aim is to further optimize the transformer on the basis of the findings, especially with respect to capacity utilization using the same system management. This is of interest because transformer capacity is being used to an increasingly higher degree in order to minimize investment costs. At the same time, transformers are being operated for longer and longer periods.
Hermetically sealed transformers in which the insulating liquid cannot come into contact with oxygen meet these requirements particularly well because aging of the insulating cellulose with inclusion of moisture is one of the defining parameters for service life. Another advantage of these environment-friendly transformers is the good biodegradability of the plant-based insulating liquid and the low inflammability of the ester liquid. This means that plant oil-based transformers can also be used in areas in which comparable oil-insulated transformers can only be operated under stringent environmental conditions, such as in inner cities or in industrial production facilities.