Transformers and its Protection

According to the patents of Károly Zipernowski, Miksa Déri and Ottó Bláth, the first transformers were produced in 1885 by the company Ganz & Co.. They were small alternating current ring-transformers or shell-form transformers. The magnetic circuit was closed jointless. The patentees used the word "transformer" for the first time.

Five years later Dolivo-Dobrowolsky invented the 3-phase-transformer. A new, improved A.C.-system for "3-times diametric voltage" was his intention. A paper published in the German ETZ in 1891 "Transmission of force with alternating currents in different phases [rotating current]" includes the first usage of the German word "Drehstrom" for "rotating current". This paper has been translated into different languages and since then the term „rotary currents“ has been accepted. To use oil for isolation purposes was proposed by Schwinburne in 1889. The company "Maschinenfabrik Oerlikon" (Switzerland) delivered in 1889 the first transformers for the utility EW Reichenhall (Germany).

With the new century several companies started to produce high power and high voltage transformers. Siemens- Schuckertwerke transformers with 12500 kVA (shell-form) and Westinghouse's 100 kV are examples of leading edge transformers at this time. With the invention of transformers, the development of transmission grids could start. Rapidly increasing demand for power forced this development in the 1920's. Huge transmission grids have been connected, the amplitudes of the short-circuit current reached substantial values, several failures in windings occurred. Due to the dynamic impact of the initial symmetrical short-circuit currents windings, arresters and bushing broke down. Short-circuit proof windings have been developed later.