Case Study: Gas-Dry Installation on 345 kV Critical Bus

Project Overview

A major Midwestern utility deployed the EMT Gas-Dry unit on a mission-critical asset where outages are rare and no energised work – including SF₆ testing – is permitted.

Gas-Dry was installed on a 345 kV transmission bus; the objective to evaluate in-field moisture reduction performance under real operating conditions.

Ambient temperatures during installation were approximately 0°C (32°F), providing an opportunity to assess performance during cold-weather conditions where moisture behavior can be affected by freezing.

Project Scope

• Asset: 345 kV bus
• Gas Type: SF₆ (SF₆/N₂ blends in certain substations)
• Objective: Evaluate moisture reduction performance of Gas-Dry
• Constraint: Limited outage window (estimated removal in 1–2 months)

Installation & Commissioning

The Gas-Dry installation was completed smoothly and without complications.

• The unit was connected using a DN20F–DN8M adapter.
• No modifications to the asset were required.
• The installation was performed efficiently within outage constraints.

Baseline Moisture Readings

Three separate bus ports were tested prior to installation to establish baseline moisture levels.

At 0°C (32°F) ambient temperature, some internal moisture may exist in a frozen state within the system. As temperatures rise in spring, previously frozen H₂O can re-enter the gas phase and temporarily increase measured PPM levels.

Recommended Measurement Strategy

Rather than focusing solely on absolute PPM values, the recommendation was to:

• Compare delta moisture values across all three ports at removal.
• Expect the trial port to demonstrate a significantly lower relative moisture level.
• Consider installing a second Gas-Dry on a thawed port in spring to further validate absorption performance under changing environmental conditions.

This delta-based approach reduces the impact of seasonal temperature shifts and provides a more meaningful performance comparison.

Operational Constraints

This 345 kV bus is classified as a critical asset:

• Outages are infrequent.
• No energised maintenance or testing is permitted.
• Removal is estimated within 1–2 months.

These conditions demonstrate the Gas-Dry’s suitability for deployment in high-value, tightly controlled transmission environments where reliability and simplicity are essential.

Key Outcomes

• Successful installation on a 345 kV critical transmission asset
• Smooth commissioning under cold-weather conditions
• Baseline moisture documented across three ports
• Clear methodology established for performance validation

This installation demonstrated Gas-Dry’s effectiveness and adaptability in real-world transmission environments. Even on critical high-voltage infrastructure with limited outage windows and strict operational controls, the unit was deployed smoothly and positioned for measurable performance validation.

Conclusion

The case reinforces three core strengths of the Gas-Dry:

1. Operational simplicity
2. Suitability for critical high-voltage assets
3. Field-proven durability with predictable maintenance lifecycle

Upon removal, delta-based moisture analysis across all ports will provide quantifiable validation of absorption performance, further strengthening the in-field performance record of the Gas-Dry system.