MV Switchgear — Live-Cleaning Without Shutdown

The scenario

A distribution facility deferring its switchgear cleaning maintenance because the only window for shutdown is a planned outage that keeps getting pushed is a common position for a reliability engineer to be in. Dust accumulation on insulators and busbars reaching levels the reliability engineer is uncomfortable with is the trigger that usually brings this kind of job forward.

The ask in a scenario like this: clean the equipment without shutdown. A site might have an existing safety case for live cleaning of LV equipment that has never been extended to MV — extending it would mean working with the asset owner’s electrical authority to develop the procedure before any work starts.

How the work would run

A live electrical job like this would be approached slowly and with extensive risk assessment.

Pre-work. Site walk-through with the asset owner and electrical authority. Risk assessment, and a safety-case extension to cover MV with the specific equipment and procedure being used. PPE requirements would include arc-rated suits, face shields, voltage-rated gloves, and hot-stick technique for any contact with the panel.

IR baseline. An insulation resistance test on each panel before any cleaning, recorded for handover.

Cleaning. Pellet feed at low pressure (60-70 PSI) — much lower than industrial cleaning. Working from the top of each panel down, with a 60-degree spread nozzle. Particulate captured by a HEPA-filtered vacuum positioned at the base of each panel.

IR retest. An insulation resistance test after each panel, to compare against baseline.

Documentation. Per-panel photo log, IR test sheets, and a cleaning record signed by the asset owner’s representative.

What a job like this typically involves

• All panels cleaned in a single day is a realistic target for a job of this scale.
• Zero shutdown of the facility’s MV system is the point of the exercise.
• On insulation resistance: we do not have a verified published source for a specific improvement figure, and independent checking found no published, sourced percentage for IR improvement from dust removal on MV switchgear. We are not quoting one here — any change in a real job’s readings would need to be reported from that job’s own before/after test sheets, not a stated “typical” range.
• A safety case formally extended to cover annual MV switchgear cleaning under the site’s electrical authority is the deliverable most sites are actually after — the harder part is always the first safety-case extension; once that’s signed, subsequent panels are largely process repetition.