Substation accident – a case study

By B Gass, Training Manager

 

Published in: Electricity+Control, March 2015 (pages 12 – 14)

Enquiries: Barry Gass cell  083 459 8298 or email bgass@vodamail.co.za

 

Read the full article on Substation accident – a case study in low res PDF format.

 

An Authorised Person had to isolate an 11 kV cable, in order to cut in a new mini substation (MSS), between a substation (S/S) and a MSS. He had already Switched, Isolated, Tested and Earthed the cable on both sides correctly.

A risk assessment had been conducted and a work permit issued, in accordance with the company’s rules and regulations. A work permit is written authorisation for work to be carried out on electrical mains or apparatus.

The circuit breaker (CB) had integral earthing and had been tested and placed in the earth position, locked off and a danger tag applied. During the course of the work, the Authorised Person had to remove the back cover of the panel (cable end box), in order to disconnect the 11 kV cable. The Authorised Person chose to identify the correct back cover to be removed by counting the number of breakers in from the LEFT hand side. He walked around the back of the panel, from the right and counted the breakers from the RIGHT hand side, instead of from the left. The Authorised Person also checked the label on the back of the panel to confirm that he was at the correct breaker. Unfortunately, this cover was a removable cover and had been incorrectly replaced on the wrong panel from a previous job that had been done.

As the cable was earthed at the MSS and the circuit breaker at the front of the panel by integral earthing, the Authorised Person decided that it was not necessary to wear a flash suit when removing the back cover and testing. He removed the back cover and decided, as an extra safety precaution, to safety test the conductors before removing the tape from the conductors. He decided to use a live tester to penetrate the insulation before removing the tape for safety. However, instead of using an approved medium/high voltage live tester, as required in terms of the company’s regulations, he picked up a low voltage multimeter to test for the presence of voltage. He also enlisted the help of his assistant to hold the multimeter, whilst he tested the conductors. The assistant was not wearing any special PPE (flash suit). On penetrating the tape, there was an explosion, causing third degree burns to 80 % of his body and his assistant sustained burns to his hands, face and upper body.

 

Take note

  • There is no substitute for safety.
  • To maintain safety, a risk assessment must exist for each task.
  • Substation staff must be trained on Hierarchy of Control to ensure the safety of personnel.