Innovative Implementation of SF₆ Online Monitoring for HV Circuit Breakers

Provider’s (TNSP) high-voltage transmission equipment to ensure safe and reliable operation.

However, SF₆ assets are prone to leakage over time, necessitating careful management. To meet the challenge of long-term net zero emissions targets, we developed an innovative method to achieve low-cost SF₆ online monitoring, proven its operability through trial installation and developed a method for quantifying the expected benefits of deployment. The LoRaWAN (Long Range Wide Area Network) technology was identified as being able to provide low-cost communications between SF₆ density transducers connected to circuit breakers (CBs) and the condition monitoring servers used for analytics and trending. A proof of concept was completed in early 2025 and the remaining population of SF₆ assets will have

LoRaWAN installed over the long term. The details of the architecture are provided in this paper. This paper largely focuses on resolving the challenge of quantifying the expected reduction in

SF₆ emissions due to the deployment of online monitoring. This required developing a methodology for creating a probabilistic model of SF₆ emission based on historical field data using reliability engineering principles. The probabilistic model is then combined with quantified environmental benefits to evaluate business case viability of installing new SF₆ monitoring devices as well as retrofitting existing circuit breakers. This paper presents a quantitative assessment of the environmental benefits derived from this initiative, focusing on the reduction of SF₆ emissions. The method for quantitative assessment of environmental benefits on SF6 emissions reduction begins with establishing the probability of SF₆ leakage events using historical top-up data from relevant existing CBs in the network. A 3-parameter Weibull distribution is then selected to model failure probability, as it best fit the observed data. The model indicates an increasing failure rate with asset age, consistent with wear-out failure modes. This statistical approach integrates both failure and censored data, ensuring a robust foundation for lifecycle predictions.

The study then estimates the average SF₆ loss per leakage event, based on our operational practices, which currently is initiated by responding to density alarms being received. The output of the model then provides both annualized cost benefit analysis and whole of life benefits based on the Australian Energy Regulator guideline of Value of Emissions Reduction

(VER). The annualized analysis can be useful for retrofit whereas the lifecycle benefit may be more useful for assessing the justification of monitoring installed at the same time of installation of new circuit breakers. The paper quantifies the benefits of SF₆ On Line Condition Monitoring (OLCM) in mitigating emissions. Online monitoring enables earlier detection of leaks, reducing both the volume of

SF₆ lost and the time required for planning and executing repairs. The benefit is proportional to the total SF₆ mass in each circuit breaker, which varies by type and location. Lifecycle benefit calculations are derived from cumulative distribution functions, providing a probabilistic model on the quantity of SF₆ emission reductions due to introduction of online monitoring. These findings provide a defensible business case to justify the cost of integrating

OLCM into high-voltage infrastructure projects, not only for operational efficiency but also for environmental stewardship.