Untersuchungen zu vogelkotinduzierten Überschlägen an Langstabisolatoren

The phenomenon of self-healing flashovers on overhead line insulators caused by bird droppings (so-called bird streamer) has been known for some time, but has so far only been investigated unsystematically. Therefore, in the first part of this contribution, an overview of the investigation methods used so far in earlier publications is given. Preliminary tests showed fundamental flaws of many previous experimental approaches with regard to the realistic simulation of the faecal jet dynamics. Based on these findings, a compressed-air driven test liquid applicator was designed, to ensure realistic conditions and reproducible tests. In the second part of this contribution the influences of the faecal jet diameter and volume on the distance-dependent flashover behaviour of long rod insulators are discussed. For this purpose, 230 flashover tests were carried out using the newly developed test equipment and a high-speed camera. The tests were evaluated with regard to the statistical flashover probability. In addition to the basic temporal sequence of the flashover process, the investigations were able to show that very small volumes in conjunction with small diameters do not cause flashovers due to the disintegration of the faecal jet caused by electrostatic forces, although their geometry would theoretically be sufficient for this. These findings and experimental observations show on one hand why this phenomenon only occurs in connection with certain bird species (large birds) and on the other hand they underline the importance of realistic tests.