High Voltage isolation near miss
- Safety Flash
- Published on 22 October 2026
- Generated on 22 October 2026
- IMCA SF 18/26
- 2 minute read
There was a high voltage isolation near miss when crew were working on a TMS (Tether Management System).
What happened?
The incident occurred during a planned maintenance task inside a high voltage junction box on the TMS. The team intended to isolate one ROV system before work started, but isolated the wrong one.
The isolation and grounding were applied to the wrong system. Believing that the correct system had been isolated, the ROV team proceeded with the maintenance task on the junction box. After the maintenance was completed, it was discovered that the wrong system was isolated and grounded. The ROV being worked on had never been electrically isolated and had only ever been switched off using topsides computer control.
No injuries, electric shock or equipment damage occurred. However, the potential consequences were severe.
What went wrong?
- Procedures were followed - but on the wrong system.
- Personnel relied on verbal confirmation rather than independently verification.
- There was no “buddy check” to verify correct system isolations.
Lessons learned
- Assume nothing: verify correct isolation — never assume isolation is in place; always confirm system identity before starting work.
- Use Buddy checks for all HV isolation and grounding tasks.
- Ensure there is clear communication maintained and that everyone involved fully understands all aspects of the job or task at hand.
- Don’t forget that Stop work authority can be exercised if uncertainty exists.
Members may wish to refer to:
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