In each edition of the Electrical Connection magazine, Dale West has included a personal story about how an incident affected someone, either the injured person, their workmates or family. This edition, he talks about the fine line between a close call and a catastrophic issue.

You know ‘close calls’ as ‘near misses’ but the term tends to make people feel like: “it missed, get over it and get back to work”. But when it comes to HV, there is a fine line between a near miss, and a fatality, and I find people are more concerned with close calls, than near misses.

Studies show that every day, somewhere in Australia, while performing simple switching operations, a fatality is avoided by the narrowest of margins. The Swiss Cheese effect is not realised because two of the holes did not quite line up perfectly, and thus the incident; does not become, a notifiable incident.

There are two common situations where this occurs: good old-fashioned mistakes like isolating the wrong equipment, and not understanding the effects of operating switchgear and ring main units on their specific ring main system.

Scenario one: Slip ring maintenance on Stacker Four

The site authorised high voltage switching operators isolated the stacker for your crew. You completed the maintenance job successfully, signed off the access permit and the stacker was ready to be powered up.

While working through the reverse steps on the switching program, the HV operators discover Stacker Two was isolated; Stacker Four was still energised. This happens often and for various reasons.

One reason is incorrect labelling. I have worked on sites where HV equipment is incorrectly labelled, and site management does not want to correct it because “that would confuse everyone; the labels have been that way for decades”.

Poorly written switching programs is a common reason. Vague instructions, repeating meaningless information, multiple terminologies for the same tasks, individual preferences on how a program should be written or executed, switching assistant/director not double-checking the correct equipment was located, correctly operated, or even worked correctly.

Switching directors interpreting what is written on the switching program instead of accurately reading exactly what is written is a very common problem.

Switching operator simply repeating instructions back to the switching director instead of verifying their position, reading the actual equipment labels and double-checking required actions.

Time, personal issues, lack of competency, site procedures, ineffective training and care factor are also big contributors.

You might ask, if Stacker Four was energised, why was no one injured? The simple answer is that no one tried to start the stacker.

If someone did try and start it, the working earths, if applied correctly, usually cause the protection device to operate and no one even knows they were in danger.

Scenario two: Isolating an HV cable for repairs

A switching program is prepared and checked. A ring main switch is opened and to make the cable safe to work on, the earth switch is closed. All seems good until calls are heard over the two-way that the whole site has just lost power. It turns out the main incomer has tripped, but they don’t know why.

They figure it was not their actions that caused the trip, because they opened the switch, de-energising the cable before closing the earth. However, at the other end of the cable, it was still energised.

This is a very common occurrence. What they fail to remember is we no longer have “line and load” in a ring system. We don’t have power in at the top and out at the bottom; there is no set configuration for how a ring main unit must be connected.

When the earth is closed, the protection device works as it is designed. Had the protection not operated, or operated slower than it is supposed to, they can be seriously burnt or quite likely killed.

Ring main units can be operated regardless of the condition of the cable at the other end.

The opposite situation happens just as often: a cable is earthed at one end they unknowingly energise the other end of the cable.

The reason for this happening is pretty much the same as the first scenario, all be it with a lack of understanding of the specific ring system on their site playing a larger role.

Unless you have installed a complex key interlocking system, the only thing preventing these scenarios from becoming a reality, are the skills of the HV operators.

This situation is more likely to occur on sites where the switching operators do not have the advantage of regularly working with the ring system. It is often said, it is hard to perform a perfect switching operation when they only switch once a month or so.

Crews that face this challenge might find it a good idea to run regular exercises of different scenarios, so they are more familiar with the task when they need to switch live. Keeping spare ‘dummy switches’ handy for the team to practice with is always a huge advantage.

These two scenarios, as serious as they are, do not help us to improve the system of work: why? Because they are not notifiable incidents; they are rarely, if ever investigated.

Because the holes in the Swiss Cheese did not line up, we wipe our brows, feel embarrassed and do the same thing next month.

Every now and then the holes match up, the protection does not operate quickly enough, and we consider it a tragic accident.

We need to vigorously investigate these ‘close calls’ and determine the root cause, to find an effective solution that prevents it ever happening again.

It is all easily avoidable.

If you know of an incident that might help people understand the hazards of HV or effects of incidents, please send your information to hv@ezylec.com