“Accessibly sealed” generation of GIS: what opportunities are enhanced with sensor integration



SF6-based GIS are known for their compactness and low maintenance. They are hermetically sealed for life, which allows their users to adopt an “install and forget” approach. The same approach however also limits opportunities to increase operational efficiencies and improve asset management outcomes: a sealed tank does not allow for predictive maintenance or repairs to be performed in case something goes wrong. This can be crucial for the grid operators, who consistently look for ways to improve service reliability, reduce maintenance costs and increase the lifetime of their GIS: it is estimated that 75% of breakdowns are eliminated by energy companies that have implemented predictive maintenance (1).


Continuous monitoring solutions exist for medium voltage (MV) switchgear which enable real-time monitoring of switchgear health and provide operators with benefits such as lower maintenance costs and reduced risk of failures. These solutions are predominantly being used in air insulated switchgear (AIS), or externally in gas insulated switchgear (GIS). However, monitoring solutions inside the critical GIS core tank are not common. This is mostly because of their usage of SF6, which results in the tank being inaccessible.


nuventura’s GIS, while keeping all the advantages of an SF6-based GIS, is based on dry air and allows for the tank to be “accessibly” sealed. This means that the GIS remains sealed and does not require any more maintenance than a traditional SF6-based GIS, but the core GIS tank can be accessed onsite to carry out remedial works if necessary. This not only reduces downtime, but also reduces the cost of having to fully replace the switchgear, or have it sent elsewhere for diagnosis in the case of an issue.


An additional benefit of is that nuventura’s GIS can be optionally integrated with an intelligent sensor system to provide real-time data about vital parameters of the switchgear’s health. To be more precise, our GIS is designed for online partial discharge (PD) and temperature monitoring using passive antennas and sensors which can be integrated into the GIS’ core tank. Increasing PD is an indicator of failing insulation in switchgear and is responsible for over 50% of failure cases (2) in GIS. Due to the stochastic nature of PD, existing preventive methods which are time- or schedule-based are ineffective at picking up failures in their early stages and often go undetected for long periods of time leading to costly failures. In addition, only about 15% to 20% of equipment failures are age related, and the other 80% to 85% are totally time-random events.


Nuventura’s PD measurement is implemented using a non-conventional Ultra-High Frequency (UHF) method based on the IEC 62478 standard. This UHF method detects electromagnetic radiation generated by discharges and is able to measure the amount of discharge and intensity as well as provide a trend of the change in discharge over time. This method can be used as a continuous monitoring system in dry air GIS. Additionally, measurement of temperature anomalies on critical components such as the high voltage conductors enable early detection of the onset of thermal breakdown. It is already widely used as an early warning detection system of insulation breakdown in other areas of the energy system such as switchgear and transformers.


The continuous monitoring of switchgear health metrics, such as partial discharge and temperature, enables a proactive digital strategy for maintenance and asset planning providing significant operator benefits compared to legacy preventive maintenance approaches. Early detection enables proactive mitigation of risks such as failures and would prolong the lifetime of these assets while also reducing the costs associated with repairs, planned time or schedule-based maintenance and service downtime.


The ability to digitise critical assets also opens up new business and revenue opportunities for ecosystem partners such as switchgear manufacturers, suppliers and service partners. Through increased digitisation, they can offer innovative products ‘as-a-service’ (such as insights through analytics of data), improved service and maintenance contracts guaranteeing uptime or provide customers with ongoing value through continuous assistance in maintaining asset health and performance. As in other industries, this also enables consulting services to further optimise switchgear performance and foster long-term relationships or cross-selling of other value-added services that improve outcomes for utilities or other industry operators.


In the era of digitalisation and automation, being able to constantly monitor the conditions of a device is becoming increasingly important. Asset performance management has the greatest value potential among all the digital initiatives, to the tune of €333 billion over the next 10 years. Utility firms across the value chain are likely to enjoy margin expansion from lower repair and maintenance costs, lower downtime of assets and fewer critical breakdowns. Integrating sensors inside a GIS can lead to significant savings in operating costs (up to 20%), while simplifying operation, extending reliability and lifetime and allowing for better asset management. However, such opportunities are only possible in a tank that is accessible – exactly what is enabled by a GIS based on dry air.


1. “Digital Transformation of Industries Electricity Industry”, World Economic Forum & Accenture report, January 2016

2. Fuping Zeng, Ju Tang, Xiaoxing Zhang, Siyuan Zhou and Cheng Pan: Typical Internal Defects of Gas-Insulated Switchgear and Partial Discharge Characteristics, 2018

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