7 Tips to Choose the Right GIS Switchgear by Leistungenergie

The selection of high-voltage switchgear is one of the most critical decisions in the lifecycle of any major electrical project. It is a significant capital investment that will define the reliability, safety, and operational efficiency of a substation for the next 40 to 50 years. While Gas-Insulated Switchgear (GIS) technology offers undeniable advantages in compactness and reliability, the market today is diverse. Not all GIS solutions are created equal.

Navigating the complexities of different designs, evolving technologies like SF₆-free alternatives, and the varying capabilities of manufacturers can be a daunting task. Making an uninformed decision can lead to a solution that is over-specified, unnecessarily expensive, or ill-suited for the long-term needs of the asset.

This comprehensive guide from the engineering experts at leistung energie provides a structured framework for the selection process. We will detail seven critical tips and technical considerations to help utility planners, consulting engineers, and project managers specify and choose a GIS solution that is technically sound, financially viable, and truly future-proof.

Tip 1: Define Your Core Technical Specifications Rigorously

The foundation of any successful procurement process is a robust and unambiguous technical specification. Moving beyond the basic voltage and current ratings is essential to ensure the GIS is perfectly matched to the grid's demands and operational philosophy.

• System Ratings: Clearly define the fundamental parameters:

  • Rated Voltage (kV): The nominal system voltage.

  • Rated Frequency (Hz): Typically 50Hz or 60Hz.

  • Basic Insulation Level (BIL) (kVp): The equipment's ability to withstand lightning and switching surges. This must be coordinated with the substation's overall insulation strategy.

• Current Ratings:

  • Rated Continuous Current (A): The maximum current the main busbars and circuits can carry continuously without exceeding temperature limits. This should be specified with a margin for future load growth.

  • Rated Short-time Withstand Current (kA): The maximum fault current the switchgear can safely withstand for a specified duration (typically 1 or 3 seconds) without damage.

• Busbar Configuration: Specify the required scheme based on your reliability and operational needs. Common configurations include Single Busbar, Double Busbar, or more complex arrangements. The choice impacts flexibility during maintenance and the overall availability of the substation.

• Bay Configuration and Quantities: Detail the exact number and type of feeder bays required, for instance:

  • Incoming Line Bays

  • Transformer Bays

  • Bus Coupler / Bus Sectionalizer Bays

  • Feeder Bays

• Instrument Transformer Requirements: Be precise about the needs for your protection and metering systems. Specify the accuracy classes, burdens, and ratios for all Current Transformers (CTs) and Voltage Transformers (VTs) within the GIS.

Tip 2: Evaluate the Physical Footprint and Site Constraints

The primary driver for choosing GIS is often the need for a compact solution. A thorough evaluation of the physical constraints of your site is non-negotiable.

• Maximum Dimensions and Weight: Obtain detailed general arrangement drawings from potential vendors. Scrutinize the overall dimensions (width, depth, height) and the transport weight of the largest single module. Ensure these align with the available space in your switchgear room, basement, or offshore platform.

• Transport and Access Routes: A common oversight is planning for the final location but not the path to get there. Verify that the largest GIS module can be transported to the site and maneuvered through access doors, corridors, or hatches.

• Layout and Modularity: Assess the flexibility of the vendor's modular system. Can the bays be arranged to fit an irregularly shaped room? Can busbars be configured to exit from the top, bottom, or side? A highly modular design can solve complex layout challenges.

Tip 3: Scrutinize the Insulating Medium: The SF₆ vs. SF₆-Free Decision

In 2025, the choice of insulating gas is no longer a simple technical decision; it is a long-term strategic and environmental one.

• The SF₆ Path (The Legacy Choice): Sulphur Hexafluoride (SF₆) is the time-tested industry standard with decades of proven field performance and reliability. Its dielectric and arc-quenching properties are exceptional. However, its extremely high Global Warming Potential (GWP) of over 23,500 times that of CO₂ makes it a significant environmental liability. Choosing SF₆ today may expose the asset to future carbon taxes, stricter regulations, and complex end-of-life gas handling requirements.

• The SF₆-Free Path (The Future-Proof Choice): Leading manufacturers now offer a range of eco-efficient GIS solutions that eliminate SF₆. These technologies include:

  • g³ (Green Gas for Grid): A fluoronitrile-based gas mixture with a GWP reduced by over 99%.

  • Dry Air / Nitrogen Mixtures: Utilising purified "Clean Air" as the primary insulator.

  • Vacuum Technology: Combining vacuum interrupters with Clean Air insulation.

  When evaluating an SF₆-free solution, ask critical questions: What is the technology's maturity and track record? Are there any differences in size, performance, or operating pressure compared to the SF₆ version? Opting for an SF₆-free solution demonstrates corporate environmental responsibility and future-proofs the investment against tightening climate regulations.

Tip 4: Analyze the Design for Reliability and Maintainability

While all GIS units are inherently reliable, superior designs incorporate features that enhance long-term performance and simplify maintenance.

• Compartmentalization: A robust design will feature a high degree of segregation. Each functional unit (circuit breaker, busbar) and each phase should ideally be in its own gas-tight compartment. This ensures that a fault in one section is contained and does not propagate to adjacent components, significantly reducing the potential damage and outage time.

• Gas Monitoring System: Evaluate the sophistication of the gas monitoring. A basic system may use simple pressure switches, while an advanced system will use intelligent gas density monitors that compensate for temperature changes, providing a true and reliable indication of the gas condition.

• Accessibility for Essential Tasks: Although "maintenance-free," some tasks are inevitable over a 40-year lifespan. How accessible are the cable testing points? How easily can the circuit breaker drive mechanism be inspected and serviced? A design that considers ease of access for these rare but critical tasks is superior.

• Vendor's Track Record: Look beyond the brochure. Inquire about the field experience of the specific GIS model you are considering. How many units are in service globally? What is their documented mean time between failures (MTBF)?

Tip 5: Consider the Level of Digitalization and Smart Grid Integration

A modern substation is a key data hub. Your GIS can be a simple electromechanical device or an intelligent, data-rich asset.

• Conventional GIS: Uses traditional, wire-wound instrument transformers (CTs/VTs). Protection and control signals are hard-wired using extensive copper cabling.

• Digital GIS: Replaces conventional CTs/VTs with Non-Conventional Instrument Transformers (NCITs), such as optical sensors or Rogowski coils. Data is transmitted digitally via fiber optic cables using the IEC 61850 protocol.

  The benefits of choosing a Digital GIS are immense:

  • Reduced Footprint and Cabling: Eliminates thousands of copper control cables, reducing cost, complexity, and installation time.

  • Enhanced Safety: Removes the risks associated with open CT secondary circuits.

  • Rich Data for Asset Management: Provides continuous, real-time data on the health and performance of the switchgear, enabling predictive maintenance and advanced grid analytics.

Specifying a digital-ready GIS is a strategic investment in the future of your grid.

Tip 6: Evaluate the Total Cost of Ownership (TCO), Not Just the Purchase Price

A common mistake is to select a switchgear based solely on its initial capital cost (CAPEX). A truly informed decision must consider the Total Cost of Ownership (TCO) over the asset's entire lifecycle.

• Initial Cost (CAPEX): The purchase price of the equipment.

• Installation & Commissioning Costs: The modular, factory-tested nature of GIS significantly reduces these costs compared to the extensive civil works and on-site assembly of AIS.

• Operational & Maintenance Costs (OPEX): The sealed-for-life, low-maintenance design of GIS results in minimal OPEX. There is no need for regular insulator cleaning or mechanism servicing.

• Outage Costs: The exceptionally high reliability of GIS minimizes unplanned outages, which can have enormous financial consequences.

• Footprint Cost: In urban areas, the land savings from GIS can amount to millions of dollars, a cost that must be factored into the equation.

• End-of-Life Costs: Consider the future costs associated with decommissioning the equipment and handling the insulating gas, especially if SF₆ is chosen.

When all these factors are considered, GIS often proves to be the more economically viable solution over its lifetime, despite a higher initial purchase price.

Tip 7: Assess the Vendor's Capability and Long-Term Support

Your relationship with the GIS manufacturer does not end upon delivery. You are entering into a multi-decade partnership.

• Engineering Expertise: Does the vendor have a knowledgeable local engineering team that can provide expert support during the crucial design and specification phase?

• Project Management & Installation: Does the vendor offer experienced project management and on-site supervision for installation and commissioning?

• After-Sales Support: What is their long-term strategy for spare parts availability? Can they guarantee technical support and emergency services for the next 30-40 years? A strong local presence is a significant advantage.

• Training: A reputable vendor will offer comprehensive training programs for your operational and maintenance staff to ensure they are fully competent in managing the new asset.

Conclusion

Choosing the right Gas-Insulated Switchgear is a complex but critical engineering decision. It requires a holistic evaluation that extends far beyond a simple comparison of price tags.

By rigorously defining your technical needs, strategically considering the long-term environmental and regulatory landscape, and thoroughly vetting the design and support capabilities of your potential partners, you can make a truly informed choice.

This decision will define the reliability, safety, and efficiency of your critical electrical infrastructure for decades to come.

At Leistung Energie, we are not just suppliers; we are engineering partners. We work closely with our clients through every stage of the selection process—from initial design studies to long-term asset management—ensuring you receive a GIS solution that is perfectly tailored to your technical requirements, budget, and sustainability goals.