Safety risks associated with HV electrical equipment at the point of imminent failure.

Richardson, Chase M. (2023) Safety risks associated with HV electrical equipment at the point of imminent failure. [USQ Project]

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Abstract

The risk of an electrical arc blast or explosion and subsequent pressure waves are a major concern with high voltage (HV) equipment that is at risk of imminent failure (ERF). Projectiles caused by the fragmentation of an ERF, and the distances that they can travel, present challenges when trying to maintain safety. This paper investigates the relationship between the available energy during an arc blast event and the distance that projectiles can travel by simulating a gapless porcelain surge arrestor failure.

The current Energy Queensland Limited (EQL) procedures for enabling ERF to remain energised is based on the Network Access Restriction (NAR). It outlines the controls that must be adhered to in order to maintain risks to As Low As Reasonably Practical (ALARP). A key component of a NAR is the establishment of a Risk Management Hazard Zone (RMHZ) which is an exclusion zone around the ERF. The current outdoor distance settings for RMHZ are typically 25 metres when there is a potential of projectiles, though this is yet to be fully rationalised.

Initial research used a primitive porcelain cylinder filled with TNT explosive to represent the surge arrestor during a simulated arc blast explosion. Advanced computational modelling, using hydrocode, were used to simulate the energy, pressure, and time required to fragment the cylinder. Modelling solutions were compared to a physics based projectile model script, which considered the available energy, drag, height, and distance a porcelain fragment could travel. The collated data from these models were analysed to determine the accuracy of each one against a known incident/event.

The time for fragmentation to occur was identified as a critical component, which through observation, closely relates to initial pressure rise. This led to an investigation into the vaporisation of internal material as a potential cause of the pressure rise. Copper was used for this analysis due to both the availability of its material properties and its common use within electrical equipment. It was identified that only a small amount of copper mass was required to be vaporised to exceed the tensile strength of a HV porcelain shell.

An electrical arc blast explosion is a nonlinear explicit time event with the projectiles expelled early in the event. This presented several challenges when attempting to predict the amount of energy available to a projectile, which modelling indicates would be hazardous during the entire flight path. It is recommended that further research, including physical testing in a controlled environment, would benefit network owners, power workers, and the public.

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Item Type:	USQ Project
Item Status:	Live Archive
Faculty/School / Institute/Centre:	Current – Faculty of Health, Engineering and Sciences - School of Engineering (1 Jan 2022 -)
Supervisors:	Ahfock, Tony
Qualification:	Bachelor of Engineering (Honours) (Electrical & Electronic)
Date Deposited:	01 Oct 2025 04:35
Last Modified:	01 Oct 2025 04:35
Uncontrolled Keywords:	arc blast; failure
URI:	https://sear.unisq.edu.au/id/eprint/52995

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