Interview: Peter Müller, Senior Manager at Pfisterer
Pfisterer at a glance
Pfisterer is a family-owned German company, with its headquarters close to Stuttgart. We employ about 2,700 people, and our revenue is about EUR 400 million (USD 425 million). The company used to be a component supplier, supplying sockets, connectors and various other components for transformers for more than three decades, but public energy grids have been our main market for almost 100 years.
Innovating transformer components
Our main solution for transformers is the CONNEX systems, which was first developed for GIS about 40 years ago. Before that, we mainly supplied contact technologies for low-voltage plants.
Having developed and patented medium-voltage dry-type connectors some 40 years ago in 1979, we then built a product portfolio aiming at higher-voltage levels, starting with 72.5 kV in 1992, making us more involved in the power transformer sector. From then on, we kept increasing the voltage level constantly, pushing the limit of dry-cable termination until we reached the 550 kV voltage level in 2015. During this whole period the focus was not only on cable termination and pluggable solutions, but also on the accessories necessary to operate and test the transformer, such as blind covers, current testing connectors, earthing connectors, etc. At the same time we also thought about protection. We have developed an entire portfolio of products for medium, high and extra-high voltage applications. So, what we have achieved is the transition from a component supplier to a solutions supplier.
Starting from medium voltages and going higher, we developed a pluggable surge arrester to offer a complete pluggable-transformer solution and an entirely touch-proof transformer. When the transformer is connected by cable, it may still be necessary to protect it with surge arresters. However, using a conventional surge arrester would be an issue as you would need to go from the cable through the air-insulated cable termination end to the surge arrester, and then back to the cable to enter the transformer, which of course does not make sense. This means that the only viable solution for a pluggable transformer is to also have a pluggable surge arrester on the transformer. This product was also added to the portfolio and continued to be developed until the implementation of a 145 kV pluggable surge arrester in 2013. We are currently developing a 170 kV pluggable surge arrester, which will be launched in 2017. All parts of the surge arrester, such as the silicone isolation around the tablets, the connection system, the housing, etc. are made by Pfisterer.
On the lower and the higher-voltage sides, the transformer can be connected by cable, by GIS or by overhead line. In any case, it is necessary to test the transformer in the laboratory during the Factory Acceptance Test (FAT). The cable, or the cable termination, needs to be connected to the socket already installed in the transformer, which requires a kind of a testing device that can be plugged into the socket to test the transformer. This was the initial reason for developing pluggable bushings. The original idea was to offer a product that would enable testing the transformer equipped with sockets, which would later be used for connecting the transformer with the cable. So, pluggable bushings were first developed for laboratory testing purposes, but pretty soon utilities called us and asked why we did not also use them during constant operation simply because they offer a lot of advantages and also eliminate the need for any oil work on site.