© THETA Ingenieurbüro GmbH 2015 Accidental Arc Expertise on Accidental Arcing   The owners of electrical equipment and installations regard the reliability of the same as an essential hallmark of quality. A situation that is extremely critical in terms of operation is the stress caused by a short circuit through an arc. Despite little probability of fault, the installation manufacturers and users pay great attention to the protection of both people and installations against accidental arcs. An arcing fault in medium-voltage switchgear can lead to a considerable pressure and thermal load of both the switchgear itself and the building in which the switchgear is located. Furthermore, the operating staff is endangered. The power loss of the electric arc, which depends on the grid topography and the geometry of the electrode layout, results in a very quick warming of the insulating gases enclosed in the installation and this, in turn, causes a pressure increase within the installation. The gases are normally air, SF6 or N2-SF6 mixtures. Due to technical reasons, the affected part of the installation cannot be switched off immediately by power circuitbreakers so that arcing times ranging from few milliseconds up to three seconds can occur. It is, therefore, of prime importance to design electrical installations that resist such incidents and thus do not endanger people's lives. Over the past twenty years we have gained both theoretical and practical experience in the field of accidental arcing. We can offer you the following services: calculation of the pressure development within switchgear sections determination of the optimum pressure relief area construction of housings from the perspective of pressure development and blowing calculation of the pressure development within switchgear buildings assessment of the wall stability within switchgear buildings and suggestions how to increase the stability increase of both the active and passive arc safety. Effects of an accidental arc in a substation Example of an Arc power Example of an overpressure in the functional unit Example of an overpressure in the building (Click the Images to enlarge them) Return to Overview