Engineering Specifications for High-Voltage Gas-Insulated Substations (GIS) per IEEE Std C37.123-2023

Introduction

High-voltage Gas-Insulated Substations (GIS) are essential in modern power systems where compactness, reliability, and safety are critical. The IEEE Std C37.123-2023 provides a comprehensive framework for specifying GIS installations rated 52 kV and above. At Keentel Engineering, we help utilities and EPC firms translate this standard into actionable specifications that improve design quality, ensure compliance, and streamline procurement.

This guide covers the essential clauses, technical requirements, and best practices that engineers must consider when specifying GIS systems based on IEEE C37.123-2023.

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Scope and Intent of IEEE C37.123-2023

The IEEE Std C37.123-2023 serves as a guide to develop procurement specifications for GIS rated above 52 kV. It focuses on the technical components and omits commercial terms. It supports engineers in drafting requirements for design, fabrication, testing, installation, and in-service performance.

Specification Format Structure

Clause 1.5 outlines a structured approach to GIS specifications, including:

• One-line diagrams
• Environmental and service conditions
• GIS component details
• Interfaces and responsibilities
• Test procedures and documentation

Keentel Engineering integrates these clauses into detailed project-specific templates for utilities.

Standards and References Used

Clause 2 lists essential IEEE, IEC, ASTM, and NEMA references. Key among them are:

• IEEE C57.13 for instrument transformers
• IEEE C37.017 for bushings
• IEC 62271-209 for cable terminations
  

We recommend including these in your reference list for any GIS procurement document.

Required Service Conditions

Clause 4 emphasizes environmental data including:

• Altitude
• Pollution levels
• Seismic category (IEEE Std 693 compliance)
  

Accurate site condition data influences GIS insulation levels, enclosure design, and structural interfaces.

What Is the Scope of Supply? (Clauses 5.1–5.3)

Divide responsibilities clearly between supplier and user. Typical user-furnished items include foundations, conduit, SCADA systems, and erection labor. Suppliers provide:

• Circuit breakers, disconnects, ground switches
• Enclosures, bushings, control cabinets
• Insulating gas and accessories
• Site services and test reports
  

Keentel project scopes include annotated diagrams like Figure 1 of the standard for visual clarity.

Proposal Requirements

Suppliers must provide:

• Drawings: one-line, general layout, gas schematic
• Gas handling procedures
• Ratings, dimensions, and weights
• Seismic calculations
• Spare parts and special tools list
  

Use Annex B to streamline bid evaluations across multiple vendors.

GIS Design Considerations

Clause 7 highlights critical design elements

• Interlocks (electrical/mechanical)
• Expansion joints and bolted connections
• External enclosures and corrosion protection
• Grounding per IEEE Std 80
• Wiring shielding and protection
  

Design details must comply with IEEE C37.122.1 and should factor in maintenance access, thermal cycling, and electromagnetic interference (EMI).

Component-Level Requirements

Each major GIS component has specific requirements:

• Circuit Breakers: Comply with IEEE C37.04 and C37.09 for dielectric, thermal, and interrupting duties
• Disconnects & Grounding Switches: Visual indicators, interlocks, and fail-safe mechanisms
• Gas System: Pressure zones, density monitoring, SF6 or alternative gases
• Instrument Transformers: Shorting terminal blocks, accessible secondary testing
• Bushings & Terminations: Mechanical strength, creepage distances, proper flanging
  

We encourage using Annex A tables to itemize component specs.

Testing Requirements

Testing is split into:

• Design Tests: Type tests like dielectric, temperature rise, and arc withstand
• Routine Tests: Mechanical operations, insulation checks, leak tests
• Factory Acceptance Tests (FATs): In presence of the user
• Field Tests: Gas quality, interlocks, continuity, and HV withstand
  

Keentel’s FAT and commissioning checklists align directly with Clause 9.

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Documentation and Quality Assurance Are Required

Quality assurance is anchored in ISO 9001. Required documents include:

• Seismic and structural calculations
• Grounding study
• Operation manuals
• Mimic diagrams and nameplates
  

Use Annex A for specifying project parameters and Annex B for collecting uniform bid data.

Conclusion

IEEE C37.123-2023 is a vital resource for high-voltage GIS engineering. It offers structure, rigor, and clarity for developing specifications that enhance GIS performance and lifecycle reliability. At Keentel Engineering, we incorporate this guide into our project workflows to ensure code compliance, technical excellence, and project success.

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FAQs on IEEE C37.123-2023 for Engineers

To support engineers, utility planners, and substation designers, we've compiled this list of frequently asked technical questions based on the IEEE C37.123-2023 standard for Gas-Insulated Substations (GIS). These answers reflect Keentel Engineering’s application of the standard in GIS procurement and design.

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