Air insulated Switchgear or AIS Substation is a type of substation where all electrical switchgear and other high-voltage equipment’s insulation to earth and between phase conductors are mainly provided by air at atmospheric pressure and where some live parts are not enclosed.
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ADVANTAGES
Cost-Effectiveness of AIS
Lower initial investment compared to Gas Insulated Substations (GIS), AIS generally requires less capital expenditure upfront compared to GIS, primarily due to the simpler design and fewer specialized components.
Proven Reliability of AIS
It has a long history of reliable operation in various environmental conditions. The components are well understood and have demonstrated durability over time. It offers high reliability in terms of performance and uptime, meeting the operational needs of utility companies and ensuring continuous power supply.
Ease of Installation of AIS
Air-insulated Switchgear substations are easier and quicker to install compared to GIS due to their simpler design and construction. They offer flexibility in terms of expansion or modification, allowing utilities to add or upgrade equipment as the demand for electricity grows without significant interruption.
Accessibility of AIS
Components in Air-insulated Switchgear are easily accessible for inspection, maintenance, and repairs. This accessibility reduces downtime and operational disruptions during maintenance activities. Routine maintenance tasks, such as visual inspections and testing, can be performed more easily, contributing to overall system reliability.
Environmental Considerations of Air-insulated Switchgear
Air-insulated Switchgear substations use atmospheric air as the insulation medium, eliminating concerns related to greenhouse gas emissions associated with SF6 gas used in GIS. They have minimal environmental impact and are considered environmentally friendly, aligning with sustainable practices and regulatory requirements.
Scalability of Air-insulated Switchgear
Air-insulated Switchgear substations offer scalability to accommodate varying voltage levels and system configurations. They can be designed and configured to meet specific grid requirements and operational needs. The flexibility of Air-insulated Switchgear allows utilities to adapt the substation layout and equipment arrangement as the grid evolves or expands, optimizing the use of available resources.
DISADVANTAGES
Space Requirements
Among the disadvantages of AIS is the substantial space it needs. Unlike Gas-Insulated Substations (GIS) or hybrid substations, which use much less space and enclosed designs, AIS substations and equipment rely majorly on air as the primary insulation. This is the fact that larger clearances between phases of various components are needed to prevent electrical arcing and flashover and ensure safety.
In densely populated areas, finding adequate space for the construction of AIS can be a daunting task. Large footprint of these substations often leads to higher land acquisition costs and getting these areas often causes delays in project implementation. Additionally, the extensive space requirements can limit the flexibility of AIS installations, which makes it challenging for future integration of bays into existing infrastructure without major modifications.
Vulnerability to Pollution and other factors
As the equipment is exposed to air, it is more prone to air pollution. Factors like, saline environments, and lightning strikes can adversely affect the performance and longevity of AIS equipment. For instance, near coastal areas, the presence of salt in the air accelerates the corrosion of metal parts, leading to an increase in maintenance and replacements of equipment.
In industrial regions with high levels of air pollution, pollutants often accumulate on insulators and other components which reduces the performance and increases the risk of insulation failure. Thus, regular cleaning and proper maintenance are essential to mitigate these effects, which adds to the operational cost and outage time for frequent maintenance needs.
Safety Concerns
Working on equipment poses increased safety threats due to direct exposure the high voltage equipment. Unlike GIS, where components are enclosed in gas-filled chambers, AIS equipment is installed outdoors without any physical barriers. This greater accessibility increases the risk of accidents due to contact with live parts, posing a great danger to maintenance personnel.
To nullify this, special training has to be imparted to personnel working on AIS. All workers must be well-versed in safety protocols and equipped with appropriate personal protective equipment (PPE) for approaching high voltage equipment safely. Despite all these precautions, the risk of accidents and injuries remains higher compared to GIS.
Conclusion
However, a large number of factors must be considered in making the decision as to which is the most appropriate technology to be used in a particular installation. Air-insulated switchgear has the significant advantage that the equipment is generally the cheapest to purchase. Unfortunately, it has disadvantages in that it takes up more space because of the clearance required in air and that the equipment is exposed to the environment. However, if there is space available for the substation, the land cost is not significantly high, and the area is not susceptible to significant salt or industrial pollution, then AIS will still be the most suitable solution for an HV or EHV substation.
