Accident Commentaries
I. Accident due to an induced effect
The job consisted in cleaning the switchgear and controlgear of a 132 kV line (line I) inside a substation enclosure.
Said line runs in parallel for a number of kilometres to another 132 kV line (line II), both of which reach the same substation.
To carry out the job, line I was discharged, opening the voltage sources, locking the cut-off elements and earthing via a circuit-breaker.
The Contact area on said circuit-breaker had to be cleaned and so was opened to do so, which meant that the disconnected line was no longer earth-protected.
When the electrician climbed up to the circuit-breaker and was about to start cleaning the device, he suffered an electric shock that caused his death.
Why did the accident occur?
- If line I was disconnected, why was the worksite live?
- The voltage at the worksite (6,000 V) was the result of the an induction effect by line II (which was in-service) over line I (which was disconnected).
How could the accident have been avoided?
- By applying the Golden Rules for working on High Voltage installations.
- The 1st Rule was correctly applied (opening with visible cut-off of the voltage sources); in this case, the power generating zone was isolated.
- The 2nd Rule was correctly applied (locking and signposting of the cut-off elements).
- The 3rd Rule was not applied (verify the absence of voltage).
- The 4th Rule was incorrectly applied (short-circuit to ground all the conductors that penetrate the work area, on both sides), as the installation was earthed only on one side, via a circuit-breaker.
