Engineering and lifetime management of outdoor HV Gas Insulated Switchgear (GIS)

GIS has been in use since the 1960’s due to its excellent insulation properties enabling compactness of switchgear and substations. The majority of GIS installations are indoor; however, GIS application outdoors is also common. The exposure of the outdoor GIS to the environment leads to maintenance challenges. A newly formed working group will investigate the optimal design and lifetime management strategy of outdoor GIS. Benefits include optimization and manufacturer guidelines to ensure increased reliability.

 

Gas Insulated Switchgear (GIS) is applied throughout the world since the late 1960s because of its excellent features such as compactness, encapsulated electrical components and to avoid failure due to environmental condition, and personnel safety with less exposed high-voltage components.

GIS substations might present indoor or outdoor use. Statistically, most GIS operated in the world are indoor use. But, because of its compactness, GIS with higher ratings have been used for the replacement of Air Insulated Switchgear (AIS) due to growing power demand or a higher transmission voltage without additional space requirements.

Fig.1 shows an example of an up-rating real project. A former Outdoor 14-bays AIS substation (300kV-50kA) was replaced after 35 years operation by a 14-Bays GIS substation (300kV-63kA).

 

 

 

Figure 2 shows an example of the rusty flange of an aged outdoor GIS after a long commercial operation caused by the poor watertight design. Figure 3 shows an example of countermeasure against flange corrosion as an appropriate maintenance which was introduced in past CIGRE activities (WGs….)

 

Therefore, an outdoor GIS is exposed to environmental conditions (rain, snow, sunshine, salt contamination etc.), and its corrosion and deterioration is accelerated rather than indoor GIS. An appropriate maintenance is therefore the key to success for long tern operation of outdoor GIS with high reliability. This is the application a new WG of CIGRE (WG B3.57 on Impact on Engineering and Lifetime Management of Outdoor) will focus.

 

This new CIGRE Working Group will cover the analysis of ‘HV outdoor GIS including Mixed Technology Switchgear (MTS)’ and will consider the following issues compared with indoor use:

1. Market and standard requirements for outdoor GIS
2. Impact on GIS design including HV connection, layout, foundation and overall substation design
3. Impact on Long-term reliability such as tightness/corrosion behavior, impact on environmental condition such as solar radiation effect, rain, snow, industrial pollution, etc.
4. Impact on operation and maintenance strategy to ensure outdoor performance.
5. Economical comparison (outdoor vs indoor) - initial and life cycle cost during install, maintain, refurbish and replace
6. Case study

 

The WG will include considerations for the Gas Circuit Breaker installed in AIS substations.

 

As benefits of this work, we could mention:

1. Recommendations for manufactures and users to increase reliability of outdoor GIS
2. Optimization of Outdoor GIS design and their maintenance strategy
3. Reduction of the risk of Power system outages, and improvement of grid availability

 

Contacts for interested professionals are:

Koji Kawakita (koji.kawakita@cigre.org), SC B3 Chair and

Toshiyuki Saida (toshiyuki.saida@toshiba.co.jp), WG B3.57 Convenor