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GIS Temperature Monitoring

GIS Temperature Monitoring is a project aimed at developing a new way of monitoring gas-insulated switchgear (GIS). It is trialling the deployment of highly accurate distributed temperature sensing equipment which will measure temperature changes along the length of a fibre optic cable wound around a GIS unit. The condition of the GIS can thereby be continually monitored by its temperature. This allows us to proactively address and repair overheating issues observed on the device.

Project-on-a-Page summary

Project data

Start date: 01/11/2020
End date: 30/06/2022
Budget: £327,000

UK Power Networks owns and operates Gas Insulated Switchgear (GIS), and some of them use Sulfur hexafluoride (SF6) as an electrical insulator. SF6 is an excellent electrical insulator. It is not poisonous to humans and has other advantageous engineering properties. However, SF6 is a potent greenhouse gas. Managing potential leaks of SF6 is increasingly important for the UK to meet its Net Zero targets and for UK Power Networks to meet its environmental targets.

There is a large population of GIS on the network that are legacy models and no longer supported by manufacturers. However, they are still in good condition. One example is the F35 GIS made by Areva (now GE). It has been identified that enhanced monitoring of this asset could be beneficial in identifying developing faults. For example, if localised heating caused by loose connections in circuit breakers could be monitored, the asset could be switched out and maintained before failure occurred.

The project will be implemented in two phases.

Phase 1: A demonstration at GE Renewable’s facility in Stafford using one of UK Power Networks’ GIS. This unenergised GIS will be heated up internally, and the attached distributed temperature sensing (DTS) system will monitor for temperature changes. This phase will serve to verify the hypothesis that heat build-up within a GIS will manifest in detectable temperature changes by the DTS system. The monitoring system will then be programmed to generate an alarm at a designated threshold.

Phase 2: The technology is then deployed to a working environment by installing it on approximately five bays of switchgear at each of two sites to ascertain whether the relationship between load and temperature can be characterised. This input will inform the level at which alarms should be set. Analysis of the site data will further augment the findings from phase one.

Fibre optic DTS technology has both a high degree of spatial and temperature resolution and typically can be used for applications where sensing is needed over a long distance (up to 4km in conventional uses). By attaching a single fibre optic cable to a DTS unit, UK Power Networks can potentially use it to monitor a full bay of five to six GIS in a single site. The load and temperature characteristics of GIS can then be monitored to determine the normal temperatures for a given load and to identify the development of hotspots in the GIS.

This project will enable early intervention, reduce disruption to customers, prevent environmental incidents and prevent damage to highly expensive GIS that is valued at approximately £1m per bay when switch room building costs are taken into account.

Through the trials, we aim to learn how a DTS system provided with a suitable alarm system can detect a GIS failure. When it does detect a failure, this project will aid in generating an understanding of the temperature changes of the F35 GIS bay as it fails.

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