Using Pressure Trends and Topping-Up Records to Support GIS Maintenance

GIS SF6 Topping-Up Technical Series — Part 5 of 5

In Part 4, we discussed remote monitoring and event records. Reviewing those records across multiple operations helps maintenance personnel understand how a GIS compartment’s replenishment needs change over time.

Pressure trends and topping-up history provide useful evidence for investigation. Their value depends on consistent measurements, complete records and an understanding of the operating conditions.

A useful review starts with records linked to the same equipment and compartment.

Bring together compartment pressure P2, topping-up start and stop times, pressure before and after filling, supply warnings and relevant maintenance activities.

Where available, retain temperature information and identify whether the pressure values are raw readings or temperature-compensated values. Record changes to sensors, pressure settings or control logic, as these can affect comparisons.

The interval between topping-up events can help identify a change in replenishment demand.

If a compartment begins requiring more frequent filling under comparable conditions, the change warrants review. First check whether pressure settings, measurement methods or operating conditions have changed.

A shorter interval is a reason to investigate; it does not, by itself, confirm a leak or quantify its rate.

A falling pressure trace should be assessed alongside temperature, measurement quality and the equipment’s operating history.

Gaps in data, sensor faults and inconsistent pressure references can distort the apparent trend. An automatic topping-up event can also interrupt a decline, making the pressure appear to recover even though the underlying cause remains unresolved.

Mark filling events on the trend so reviewers can distinguish replenishment from other pressure changes.

[Insert an illustrative pressure trend with topping-up events and maintenance annotations.]

Figure 1. Event markers add context to pressure trends. Any example curve should be identified as illustrative rather than actual operating data.

Changes in filling duration may also deserve attention, but duration alone does not establish the amount of gas added.

Supply pressure, regulator settings, valve operation and the difference between starting and stopping pressure can all influence an operation.

Compare duration alongside these conditions. Where gas consumption reporting is required, use an appropriate quantity measurement method rather than deriving SF6 mass directly from elapsed time or pressure readings.

A practical review process is to:

• Identify a change from the compartment’s previous pattern.

• Check data quality, settings and operating conditions.

• Arrange inspection or leak investigation where indicated.

• Record corrective work and verify its outcome.

• Continue monitoring under comparable conditions.

Review criteria should be agreed for the equipment and maintenance programme. A universal number of filling events or a single pressure-drop threshold should not be assumed suitable for every installation.

Across this five-part series, we have covered the topping-up sequence, P1 and P2 monitoring, gas circuit protection, remote visibility and maintenance review.

Together, these functions support a more traceable replenishment process. Automatic topping-up maintains the configured filling cycle; repeated replenishment still requires attention to the cause of gas loss.

Explore the series:

1. How an Automatic SF6 Gas Topping-Up System Works for GIS

2. Monitoring GIS Compartment and Gas Cylinder Pressure During SF6 Topping-Up

3. Pressure Control and Safety Protection in Automatic SF6 Topping-Up

4. Remote Monitoring and Data Logging for GIS Gas Topping-Up Systems

5. Using Pressure Trends and Topping-Up Records to Support GIS Maintenance

Contact KSTONE to discuss pressure monitoring, topping-up records and the information needed for your GIS maintenance workflow.

Email: info@kstone-sf6.com
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