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Maribor, Slovenia

Size or capacity

400/110 kV

Investor / Client


Time period


Description of Facility and Services

After 1971, a new voltage level became an issue of discussions in Yugoslavia, firstly in connection with a great new Djerdap HPP construction and an OH transmission line connection running down to Belgrade. Later on, an idea to connect the whole Yugoslavia occurred, whereby different concepts were examined. At the beginning, the idea of a “spine” connecting Belgrade – Zagreb – Ljubljana prevailed. However, already at an early stage, the idea of a loop which would better connect the Yugoslavian production sources with consumption, firstly fostered by Dr. Vidmar and later on studied and professionally argued for by Dr. Plaper, became very important. It was placed (quite visionary at that time) in order to get close to the then aspirations of connection with the Western European network. So in 1973, an intensive design engineering work started at IBE which should enable construction of a network expanding at its first stage across Slovenia. This first stage encompassed an OH transmission line running from Zagreb via Krško (the NPP was only in its early stage) to Maribor and onward via Podlog to Ljubljana. This was the so-called »northern branch« of the 400 kV loop. However, the things were anything but easy. In Slovenia, there was a great opposition between experts who claimed that there was no need of a 400 kV level since the 220 kV one was only just constructed. There were also other big discussions relating to a one-line diagram on a 400 kV side. Some of them opposed to our suggestion regarding double and auxiliary bus-bars claiming that the switchyard in Maribor was not so big to justify the auxiliary bus-bars. It was only after a great deal of troubles that we succeeded to convince them of the opposite. A long-lasting operation justified our solutions of that time.

Spatial problems were met as well, starting with the issue of where the Maribor substation should be placed at all – taking into consideration the fact that the existing Cirkovce substation was not so far away. Silently glancing towards future connection with Austria, the location in Dogoše prevailed. Moreover, we contemplated already upon a big pumped storage plant construction in the Drava valley. At that time, we didn’t only start taking over a new technology on a HV level with completely new issues (coordination of insulation, electrical magnetic impacts, problems of long lines, short-circuit conditions), but skipped also into a new protection and control technology. The first protection systems based on electronic sets appeared and the first computers providing operation monitoring were introduced.

During the years of 1975 and 1976 the substation was in course of an intensive construction work and according to the plan it was accomplished at the end of the same year. However, a part of network connecting Zagreb and Ernestinovo which should have supplied electricity from the already operating 400 kV network in Serbia, hadn’t been constructed yet. So, the voltage was at first established by an isolated operation of a part of the 110 kV network in Mariborski otok HPP and by transformation to 400 kV. On December 29, 1976 Slovenia got its first supply on the 400 kV voltage level. In the year to follow, the connection between Zagreb and Ljubljana (Beričevo substation) was established and up to 1978 the operation of the northern loop of the “Nikola Tesla” network (the name was given in 1976) extending from Djerdap to Ljubljana was provided. During all these years, the Maribor substation has been operating successfully. In 1980, it faced an extension providing due 400 kV connection towards Austria.

For the above described project IBE provided preliminary designs, a basic design, a part of tender documents within joint supplies of JUGEL, design for obtaining Construction Permit, detailed design, as-built design and operating and maintenance instructions.

From 2006, the Maribor substation has been in its new reconstruction stage encompassing high voltage equipment and control and protection systems. IBE cooperates again in all design engineering works.

IBE d.d., Hajdrihova ulica 4, SI-1001 Ljubljana, Slovenia
Telephone: +386 1 4776 100
Fax: +386 1 2510 527

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