Following the switching by the client one team of service engineers set to work to rack out the LV ACB (LV side of transformer H2) and another racked out the Vacuum C-B on the HV side. The HV team racked out the carriage and lifted to ground level with the aid of a trolley and then switched to earth, once racked the Service engineer switched to earth. A safety lock and caution sign (LOTO) was fitted to the earth switch once applied.
The HV Circuit-breaker was then handed to another team for planned preventative service, the HV team proceeded to check the LV side which was also complete with the ACB withdrawn and brought to ground level via trolley for service. It was at this point the HV team proceeded to open the transformer enclosure in order to test for dead and discharge the circuit from any additional charge.
At this time the Permit-to-work documentation was neither issued nor communicated to the HV team The Service Supervisor had confirmed the HV and LV withdrawal of the C-B’s and application of earthing and signed the permit and also had obtained client sign on, however no indication of this was given to the members of the work party of this. A permit-to-work is a systematic way of ensuring all safety controls have been performed and confirmed prior to the commencement of works for a given period of time. Once all controls (isolations and earthing in this instance) were confirmed this should then be effectively communicated to members of the work party to ensure all persons are aware of the controls, equipment to be worked upon and details of the risks faced by adjacent LIVE equipment.