Modern Subterranean Substations in GIS Technology – Challenges and Opportunities in Managing Demographic Change and Infrastructure Requirements
Bert Strassburger, Peter Glaubitz, Siemens AG, Energy Sector, Germany

1. Summary
This paper outlines the opportunities the use of modern subterranean substations offers and the challenges we face. For more than 40 years proven gas-insulated switchgear (GIS) has helped to secure efficient energy supply. It is suitable for various urban or industrial settings, e.g.

  • Vicinity of public buildings
  • Subway stations, plazas or parking lots
  • Stadiums, parks or recreation areas
  • Historic or religious places
  • Off-shore wind parks or oil platforms
  • Hydropower stations

Furthermore, the adaption to different design-concepts, e.g.

  • Underground substation
  • Semi-underground substation
  • On-top building

provides additional architectural flexibility.
Modern subterranean substations have to be “invisible”, i.e. perfectly integrated in the surrounding area. Challenges such as access routes, emission control, fire protection, soil or ground water have to be solved by combining established know-how and experience. Local expertise and partnership are essential for obtaining approval from the respective authorities without problems as well as for on-time completion and reliable long-term operation of the substation.

Examples of existing installations and installations under construction are presented. These references show a wide range of situations and solutions and document how modern subterranean substations contribute to assuring economical and environmentally friendly power supply.

2. Introduction
Energy supply today and in the future presents major challenges to the infrastructure. Demographic dynamics, scarcity of resources and the increasing environmental focus are
three global trends in the energy sector.

  • Population growth followed by an increasing demand for power and power supply in
    urban and rural areas require reliable transmission of large amounts of electricity as
    well as grid stability.
  • The shortage of fossil fuels warrants cost-effective energy solutions, long service life and low lifecycle costs.
  • Climate change calls for low energy losses, and environmental protection.

Modern high voltage products and solutions provide answers to these multifaceted market requirements. Space-saving gas-insulated switchgear with 25-year maintenance cycles, highpowergas-insulated lines, low-noise transformers and state-of-the-art energy automation systems contribute to managing the global challenges.

Figure 1: Three global megatrends in the energy sector
Figure 1: Three global megatrends in the energy sector

3. Substation Site Constraints and Implementation Criteria
The cost reduction facilitated by getting high-capacity connections at transmission voltageclose to a city’s distribution network and its load makes up for design-related challenges. These are due to the fact that certain issues, such as environmental impact and public safety need to be addressed when designing substations and their components for inner cities. The following parameters have been identified as important for inner city substations:

  • Limited size of the substation area due to limited availability of space and the high
    cost of land: This calls for a very compact multi-level substation design.
  • The proximity and number of neighbors and neighboring activities require a very low
    environmental impact of the substation in terms of visibility and noise as well as
    electric and magnetic fields.
  • For the same proximity reasons public safety requirements of the substation are very high and the assessment of failure consequences is a major criterion for component and substation design.
  • The high-voltage switchgear installed in the substation must be of the highest quality based on proven designs. Its implementation requires extensive operational experience.

4. Subterranean Substations – a Solution Providing Great Benefit
More and more areas in the world require suitable solutions that fulfill their individual sdmands. Gas-insulated switchgear (GIS) is known for its efficient energy-supply capabilities. It can be used for a great variety of urban or industrial situations. Thanks to its compact and modular design GIS allows directly connecting inner city nodes to the highvoltage and extra-high-voltage networks, reducing transmission losses and enhancing energy efficiency. Furthermore, GIS provides great architectural flexibility as it can be adapted different subterranean design concepts, such as :

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