Investigation of Transient Currents on Salt Contaminated Polymeric Insulator Surfaces

To prevent potentially fatal electrocution when a construction crane accidentally touches a power line a load bearing electrical insulating link can be used. This is placed between the crane hook and the load to prevent electrical conduction through the crane and load to a "Rigger", a person guiding the load from the ground. An investigation of laboratory testing procedures of salt contaminated polymeric coated crane insulating links was observed to display transient earth-leakage current during clean-fog testing. These transients were shown to be related to the amount of water reaching the surface and the time between energizations at power frequency ac voltage. Investigation of these transients is described in this paper. Results allow three types of transient waveform to be identified, each appearing at different periods during the 1 hour fog tests performed. The greater the water flow rate supplying fog to the test chamber the more rapid is the transient behaviour progressed through the 3 types identified. A hypothesis of the surface and contaminant behaviour is offered to explain the observed results.