Many overhead transmission lines in the Netherlands are multi-circuited; when one circuit is de-energized for maintenance, the other remains energized. The energy transition necessitates more transmission line reinforcements and heavier loading of existing lines to meet the increasing power demand, consequently increasing the need for additional linework. The energized circuit induces a voltage (EMF) and current in the circuit being worked on. As a further safety measure, line workers utilize a portable earthing device (PED) that is attached to the de-energized circuit’s conductors. The induced voltage and current in the circuit can cause arcs up to half a meter long when attaching or detaching the PED, posing a serious threat to workers’ safety. There are no active mechanisms in place to stop the arc, so it must naturally extinguish in air.

This thesis aims to model and characterize naturally extinguishing arcs in air. There is little available literature on this topic, which primarily consists of models for static free-burning arcs in air. There are two key objectives in this research: (1) develop a mathematical expression describing the behaviors of naturally extinguishing arcs in air and (2) use the derived expression to produce an arc model simulation verifying the expression’s validity and accuracy. The provided test data, including arc videos and oscilloscope data, encompassed arcs under various testing conditions and utilized a test setup that mimicked the arcing environment of a PED being detached from a conductor. The arc distances were approximated using MATLAB image processing techniques due to the videos’ poor quality in showcasing the arc distances. These approximated arc distances and oscilloscope data were examined and manipulated to develop an overarching arc expression that represents the resistance-current relationship evident in free-burning arcs in air. Two expressions were derived for comparison: a logarithmic expression and a power law expression. These expressions were implemented in two separate ATP-EMTP software models that each utilized a MODELS-language module to represent the arc for simulation.

The resulting resistance and voltage-current characteristics of the two models were compared against the original test data. The power law expression was found to be the more accurate of the two models. Different testing conditions were then applied to the arc model to identify their natural arc extinction distances, which were also compared against the original test data. The results establish that the power law expression arc model sufficiently predicts the natural arc extinction distance. These predictions can be improved in the future with more precise test data. This thesis’s research fills a gap in the existing literature on modeling natural arc extinction in air. The findings of this research can influence future safety procedures for the line workers who experience these arcs. Furthermore, the results of the arc model for PED removal can potentially be expanded to describe the arcing behavior of disconnectors during bus transfer assessment, leading to a greater understanding of disconnectors and providing a deeper insight into their application and test result interpretations.