Mind Your Safety

Entering Outdoor Substations, Part 1 of 8

If you’ve never entered an outdoor substation before, the equipment may be completely foreign to you. A substation, though, is merely one of a series of connection nodes between a generating station and an end user.

Where you are in North America determines which grid you walk into, all of which are interconnected. The reliability of the North American utility grid is the responsibility of NERC (North American Electric Reliability Corp.), which manages eight grids or regional entities (Google NERC maps to see them all).

The benefit of this system is redundant supply within each grid; should one generator go down, the rest will share the load to keep the lights on. It also means that when a fault occurs in your substation, every generating station in your grid wants to feed energy to the fault (limited only by the impedance of the system). This means that problems with one utility can be transmitted to neighbouring utilities—even an entire grid, as happened to NPCC in 2003.

If you are a small non-residential facility, you are likely fed from one small substation with one set of high-voltage primary lines feeding one transformer in the station, and another set of secondary lines feeding your facility—either at a reduced high voltage or at a low voltage. Your facility will depend completely on this one power source, called a radial system.

Upstream in the electrical system will be a more complex substation that will have one set of lines coming in and multiple sets of lines going out, and it is part of the interconnected grid system. These multiple lines can both feed other substations and entire communities, or major users who want to be fed from the interconnected system for redundancy.

The input/output voltages of this substation will be higher than in the radial system. Further up the system will be more complicated substations with multiple lines going in and out with higher voltage levels on both primary and secondary (these are the 230kV to 800kV boys).

Then you’re back at the transformer yard outside the generating station where the transformers are stepping up the generator output voltages to match to the regional transmission grid.

Regardless of the substation you are entering, there are some common sense and historically validated safe work practices you should follow. As you approach a substation, its appearance can indicate the quality of the maintenance. For instance, the crushed gravel that is in every substation is there to limit step potential during a fault event. Weeds growing up through the gravel, or blackberry bushes coming through the fence, means someone is not doing—or does not know to do—their job. During your approach, visually check for broken insulators, storm damage, snow, ice, puddles, vandalism, whether Danger signs are in place, and that the gate is locked.

In a world of high-value copper, look and see whether the copper grounding is still in place. There should be ground wires and ground jumpers from the fence into the ground along the fence and, particularly, attached to the gates. I was in a 60 kV substation in Toronto where every lick of copper had been stolen since the previous inspection (such an incredibly dangerous thing to do). Someone sent me horrible pictures of two guys roasted in a Texas substation as they were trying to remove copper and, inadvertently, became part of the electrical system.

As you approach the gate, and everything seems in place, take the back of your arm and slowly hold it close to the fence. If the hair on your arm starts to rise, there’s a problem. If the hair does not raise, take the back of your hand and quickly and lightly touch the fence. Do you feel any tingles? (However, it is unlikely you will feel the tingle of low voltage if you’re wearing insulated boots on dry ground.) A tic tester could be effective for determining whether there is induction on the fence but, due to general induction, it may give you a false positive. Regardless, if you have felt no tingle on the back of your hand, then you can likely unlock the gate and go in. Lock the gate behind you; you do not want to be responsible for someone entering after you without permission.

Until next time, be ready, be careful and be safe.©

Canada Training Group has been providing consulting services to industry since 1980; Dave Smith, the president, can be reached at davesmith@canada-training-group.ca.