Gefahren durch Störlichtbogen

Vortrag wurde gehalten zum Technisches Symposium im Rahmen der Generalversammlung der IVSS, 8. Juni 2005 DresdenSymposium ISSA Electricity Section, June 7-8, 2005, Dresden/Germany,Abstract: Almost all short-circuits in electric power installations are accompanied by electric fault arcs. These arcs are huge energy sources. Energies converted during an arcing fault at the fault point are in the range of some Megawatts depending on the shortcircuit capacity of the electric power system and the clearing time of the protection devices. The temperatures in the arcs exceed 10,000 °C. Besides the thermal and dynamic current effects, fault arcs have direct destroying impacts to the equipment related, and are very dangerous for human injury for this reason. There may be a direct or indirect exposure of persons by the arcs. Exposures are the strong radiation and heat flux, the sound effect, the pressure rise, the hot metal splashes, vapours and particles resulting from the arcs. In the paper, these hazards are analysed, based on extensive investigations in the high power test lab. Exposures are quantified and compared with physiological limits.Zusammenfassung: Fast jeder Kurzschluss in einer elektrischen Anlage ist von Störlichtbögen begleitet. Diese Lichtbögen setzen große Energien frei. Die Energie, die bei einem Störlichtbogen am Fehlerort umgesetzt wird, liegt im Bereich von einigen Megawatt je nach Höhe der Kurzschlussleistung des elektrischen Netzes und der Ausschaltzeit der Schutzeinrichtungen. Die Temperaturen innerhalb dieser Lichtbögen überschreiten 10000 °C. Neben den thermischen und dynamischen Wirkungen der Kurzschlussströme besitzen Störlichtbögen unmittelbar zerstörende Auswirkungen auf die betroffenen Anlagen und bergen von daher große Verletzungsrisiken für Personen in sich. Die betroffenen Personen können einem Störlichtbogen dabei mittelbar oder unmittelbar ausgesetzt sein. Gefahren durch Störlichtbögen bestehen in einer intensiven Strahlung und einem starken Wärmestrom, einer Schallentwicklung, einem Druckanstieg sowie der Entstehung metallischen Dämpfe, Metallteile und Spritzer. Im Vortrag werden diese Gefahren auf der Basis von umfangreichen Untersuchungen im Hochleistungs-Prüflabor analysiert. Die Lichtbogenwirkungen werden quantifiziert und mit physiologischen Grenzwerten für den Menschen verglichen

Testing of PPE for eye and face protection

The performance of personal protective equipment (PPE) and its contribution to increase personal safety in usual work places has to be proven by tests. One potential hazard for people are electric fault arcs occurring with short-circuits in electric power installations. There are very high risks for persons especially in case of direct exposure, e.g. during live working or working in the vicinity to live parts. Particularly radiation and convective heat is converted. With the box test according to IEC or EN 61482-1-2 a method for testing protection textiles and clothing against the thermal hazards of electric fault arcs has already been existing and used in certification for several years. But as shown by arc accidents the face is also particularly affected by severe damages. Protective equipment for eye and face protection which is also tested for arc resistance and protection is necessary. Based on basic investigations test principles for eye and face protection equipment against the thermal hazards of electric fault arcs have been developed and laid down in a new German test guide. The test set-up of the box test is suitable. It has been adapted and modified by a test head where test samples such as visors, visorhelmet combinations, face shields etc. are placed. The tests are carried out in accordance to the box test method of protective clothing (IEC/EN 61482-1-2). The paper gives information on tests made according to this test guide. Furthermore general conclusions are drawn on how to test and how to standardize tests of PPE for eye and face protection. The principles will be introduced in E DIN 58118 becoming a supplementation to the German edition of EN 166. It can also be the base for an international or European standard later on