Alstom Technology Limited

Erland Soerensen

Reinhard Joho

Richard Blatter

Sture Lindahl

Goeran Lindahl

The invention relates to a method for detection of a ground fault (), which occurs in the vicinity of a neutral point (), in a polyphase electrical device which is operated at a fundamental frequency, in particular an electrical machine () or a transformer which has a number of windings (), which are associated with the individual phases, one end of each of which windings () is connected to the neutral point () and the other end of each of which windings () is connected directly to a power supply network via a power supply system connection (). Simple and reliable detection is achieved in that the change in the physical variables which is associated with a ground fault () is measured in the immediate vicinity of the ground fault (), and is evaluated.

Method for detection of a ground fault, which occurs in the vicinity of a neutral point in an electrical device, as well as an apparatus for carrying out the method

A generator for producing high voltages and having at least one generator winding () is connected via a generator circuit () to a network (), which generator circuit has means () for protection against overvoltages. Improved protection against higher voltages is achieved in that the at least one generator winding () is subdivided into a number of winding sections () whose winding insulation is designed such that the insulation level is graduated, and in that the overvoltage protection means have a number of overvoltage protection elements (), which are associated with the respective individual winding sections () and whose response levels are matched to the requirements of the associated winding section.

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Västerås, Sweden

Erland Soerensen