GAS INSULATED SUBSTATION

The metal-enclosed gas insulated switchgear inherently follows the criteria for new substation design and offers a higher reliability and flexibility than other solutions. Due to the gas enclosed design, GIS is the most suitable solution for indoor and underground substations.

GIS configurations can be applied to any type of bus bar arrangements:

• Single busbar,
• Double busbar
• Single busbar with transfer bus,
• Double busbar with double circuit breaker,
• One and a half circuit breaker scheme and
• Ring busbar.

GIS performs the same function as AIS. The compact and metal-enclosed design of GIS has prominent advantages and better performance than AIS. However, the high initial investment is a key obstacle in expanding the application of GIS.

In remote or rural area, industrial areas or in developing countries, AIS is still the best choice. In places where the cost of land or cost of earthworks is high or where the sceneries cannot be disturbed by AIS, the solution is to use underground or indoor GIS.

For a better appearance, an underground GIS substation can be design with an aesthetic view that hides its presence. The existence of a substation could be designed so that it cannot even be recognized .

Economics – Life cycle cost (LCC) comparison

Regarding economics, initial capital investmentis not enough to evaluate the overall substation project. Life Cycle Cost (LCC) should be considered, including primary hardware cost, maintenance cost, operation cost, outage cost and disposal costs.

1. Primary hardware

Primary hardware for primary equipment, GIS is more expensive than AIS. However, the price of auxiliary equipment such as support, conductors, land, installation, control, protection and monitoring can lead to a cost difference between the two systems being small.

2. Maintenance

The failure rate of circuit breaker and disconnecting switch in GIS is one-fourth of that of AIS and one tenth in case of busbar, thus the maintenance cost of GIS is less than that of AIS over the lifetime.

3. Operation cost

The maintenance cost of GIS and AIS shall be equivalent. The cost for training in GIS is higher than in AIS.

4. Outage cost

Since the failure rate of GIS is lower, the outage cost of AIS shall be greater.

5. Disposal cost

The cost of decommissioning and disposal after use should be capitalized. The value of future expense must be taken into account.

source:http://electrical-engineering-portal.com/