Entering Outdoor Substations, Part 1 of 8
Dave Smith has been an Industrial Maintenance Electrician since 1975. He has taught maintenance, troubleshooting and safety courses to thousands of electricians in mines, mills, refineries, factories, plants, power stations and offshore platforms throughout North America and the Middle East. Dave is a hands-on guy and teache...
High voltage and the hair on the back of your arm.
Seeing the insides of an outdoor substation for the first time can be quite a unique experience for anyone, regardless of their experience and background. Within the big picture of an entire energetic system, a substation is the small connection point transferring the electrical energy from the generating station to the end consumers.
Depending on your location, you will find yourself faced with different grids which are ultimately interconnected. The optimal performance of the North American utility grid falls under NERC - North American Electric Reliability Corp’s responsibility which oversees all the eight grids or regional entities that make up the North American utility systems network.
We’ve all heard the old saying: never put all your eggs in one basket. I think it’s safe to say our industry surely preaches and practices this idea in its philosophy. Case in point: if one generator registers a failure, others take over its function and energy feed continues uninterrupted - this being a major advantage. But there is a downside as well - helping hand generators risk to also take over the problems of the faulty generator and this state can quickly spread to the entire grid as experienced in the 2003 NPCC event.
Industrial, non-residential, small facilities are most likely serviced by… an equally small substation having a primary set of high-voltage lines, that feeds a single transformer. Near them, a secondary set of lines feeds the above-mentioned facilities with a reduced high-voltage or low-voltage power. This is the so-called radial system, a system depending entirely on just one source of electrical power.
Up one level, in the electrical system, we find a slightly more sophisticated substation having a set of lines entering the substation and, this time, multiple sets of lines going out, feeding either other small substations, or big consumers who feed directly from the interconnected system for the very reason previously mentioned, power redundancy.
Logically, both input and output voltage levels of this substation are significantly higher than those handled within the radial system. Going yet one more level up we reach the big energetic cavalry system, a network of more elaborated substations with multiple sets of high-voltage lines at both sides supplied by 230kV and 800kV hulks.
Finally, we get to the generating station’s gang of transformers which convert the generator’s output voltages to levels that fit the specifics of the regional transmission grid.
There are a couple of things to be observed and considered every time you enter a substation. Many of them particularly address your safe work knowledge. One important thing to watch for is the presence of crushed gravel, as it serves as a limitation of the step potential in a fault event. You should also pay attention to the external, physical look of the substation since this will be your first clue on the quality of maintenance. If for example, you can see weeds popping out from the gravel or green bushes climbing the fence, then it’s clear that those in charge with maintenance are either careless or too poorly prepared to get the job done correctly. Also, check for damaged insulators, weather damage or even evident signs of people getting destructive. Finally, any source of harm for the physical integrity or life of the workers should be clearly marked by a danger sign.
After completing the preliminary checks above, also make a habit of verifying if the copper grounding is still in place. I once visited a 60kV substation in Ontario which had been plundered of all its copper. In the rare event in which a thief steals the copper grounds without becoming part of the electrical system, the system is now highly dangerous and should not be entered.
Only approach the entrance when everything else seems to be in safe. Before unlocking the gate, test its state by placing your hand in close proximity. Don’t touch the fence! See if the hair on your arm starts raising, that’s one loud telltale sign of danger. If nothing like that happens, you may want to very quickly and lightly touch the fence with the back of your hand. Any tingles? If not, don’t get too comfortable. If you wear insulated boots on the dry ground, you cannot expect to feel any tingles. An alternative to this popular solution is a tic tester but even it can give you false positive results sometimes. However, if during the first test you’ve felt no tingle, then it’s safe to unlock the door. Don’t forget to lock it behind you, before some other unmentionable event is triggered by unauthorized visitors!
Until next time, be ready, be careful and be safe. ©
