May 27, 2005
Engineering Department
VAC, Part 2
As I mentioned in my last entry, we're having a few electrical problems at our house. ComEd is supposed to supply voltage at 120VAC (Volts Alternating Current). That's just a nominal value, it can vary a bit. ANSI standards supposedly permit 5% variation, from 114 volts to 126 volts. ComEd's rule book says they may have 5.8% variation, from 113 volts to 127 volts. This past week, I'm measuring anything from 133 volts to 139 volts. The speakers attached to my wife's PC blew out last week, and one of the 300W quartz-halogen lamps burnt out a few days ago.
I've called ComEd twice, and they haven't fixed it. On Monday a truck came by and they took a look at the transformer drum mounted on the pole in the alley behind our house. (Here's a few pictures of a transformer drum at HowStuffWorks.) However, since then nothing has happened. I've been compulsively checking the line voltage ever since with my DMM (Digital MultiMeter). It was 137 volts just a few minutes ago.
There must be tens of thousands of transformer drums in the city of Chicago alone, so ComEd must be replacing them all the time. I've been wondering why they haven't replaced ours yet. The rule book says that voltage shall not exceed 127 volts for more than one minute, but it's been more than that for a whole week.
I think I've now got it figured out. I was restless tonight (this morning) and couldn't get to sleep, so I took a walk. I took my DMM with me. I was looking for outdoor outlets. I wanted one right on the side of the building, so I could get to it without entering anybody's backyard.
Down at the end of the block is a small apartment building that has an outdoor outlet in their parking lot. I flipped on the DMM, turned on the backlight for the display, flipped up the cap on the outlet, and stuck in the probes. 138 volts AC. Bingo.
All the buildings on that end of the block are fed by a different drum transformer than our building. That means the problem is not in the transformers in our alley. The problem is further upstream in the distribution grid, at some substation nearby. It's a bigger problem that's taking longer to fix.
The drum transformers tap into three-phase lines running high up on the utility poles. Both transformers I tested are attached to the same phase. I walked down the street in the other direction to where the buildings were on a different phase and found an outside outlet I could get to, but it wasn't turned on. I wonder if all the phases are affected?
Anyway, now I have a plan.
This high voltage is against the rules for electrical service in Illinois. It damages delicate equipment, strains motors, and causes light bulbs to burn out faster. It also raises peoples' electric bills.
Maybe tomorrow I'll follow the power lines a little further and find a few people who will let me check their voltage, especially in some of the businesses on Milwaukee Avenue. If enough of us bitch to ComEd about the problem, maybe they'll hurry up and fix it.
.
Leave a comment