Yes, you can perform SF6 gas purification while high-voltage equipment is energized, but it requires a specialized Online SF6 Purification System (often referred to as an "online kidney" or "breathing system").

Performing this task on live equipment—often referred to as live-line operation—is a highly technical procedure that must adhere to strict safety standards, such as T/CEC 424—2020.

Here is how the process works and the critical safety measures required:

1. The "Breathing" Cycle Principle

To purify gas without a power outage, the equipment acts as an external circulation loop. It connects to the gas chamber's existing valves and "breathes" the gas out, passes it through a multi-stage filtration system, and returns it to the chamber in a continuous loop.

2. Critical Safety Constraints

For the equipment to remain energized safely, the purification unit must manage three primary risks:

• Pressure Stability: This is the most critical factor. The unit must maintain a constant internal pressure within the GIS (Gas Insulated Switchgear). Professional systems, like the SF6 purification cart, use PLC controls to ensure pressure fluctuations stay within ±0.01 MPa. If the pressure drops too low, the insulating properties of the gas fail, leading to an internal flashover (arc).

• Moisture and Decomposition Removal: The system must use specialized molecular sieves and chemical adsorbents to remove SO2, HF, and micro-water in real-time.This prevents the formation of corrosive acids while the switchgear is under load.

• Particulate Filtration: Conductive dust or metallic particles generated by moving parts must be filtered out (typically down to ≤ 1 um) to prevent them from bridging the gap between energized components and the grounded tank.

3. Advantages of Online Purification

• No Power Outage Required: You avoid the logistical complexity and lost revenue associated with scheduling a substation shutdown.

• Dynamic Monitoring: Most online units provide real-time data on the current state of the gas, allowing you to see the purity levels improve as the cycle progresses.

• Predictive Maintenance: By treating the gas while the equipment is under load, you address degradation at its source before it causes an insulation breakdown.

4. When Not to Perform Online Purification

While online purification is a powerful tool, it should not be used if:

• The equipment has a suspected structural leak (indicated by rapidly dropping pressure).

• There is a major internal fault already in progress.

• The gas chamber's valves are damaged or inaccessible for a secure connection.