Oops.
Tuesday, December 29, 2009
Monday, December 28, 2009
How to Capture and Visualize 60Hz
Boring electrical geek ramble here.
100 years ago, many AC systems were operated at 25Hz (25 cycles per second), and pretty much anyone could detect it when looking at a light bulb. You could see it pulsing really fast. At today's 60Hz, it is pretty much impossible to detect that pulse in an incandescent light bulb, because the filament does not have enough time to noticeably dim between the 60-times-per-second pulses.
Unlike incandescents, fluorescent lights visibly pulse to some people whose eyes are sensitive enough. Like mine. I can see the flicker of computer monitors set to 60Hz, too. Both give me headaches. Many monitors have configurable frequency settings, so I change them to as high a setting as possible. If I can't, the monitor is disposed of.... somehow I usually find a way. And of course I avoid using fluorescent lights as much as possible.
But there's a relatively new flicker-detectable 60Hz light source out there, and I probably can't run away from it: Cheap LED lights.
LEDs are either ON or OFF. There is no 'warmup' or 'cooldown' interval.
Have you ever seen one of those spinning light gadgets sold at gift stores, with the LEDs on it? As they spin, the lights make various multi-colored solid lines or dashes or dots, rotating back or forward, and they are fabulous for mesmerizing cranky 2-year-olds for a few minutes.
Next time you get your hands on one of those, grab the spinner so it can't turn, and then turn the thing on. These are battery-operated, so they are not strictly 60Hz, but run at variable frequencies controlled by the internal circuitry. You'll note that, when the spinner is not spinning, the LEDs are constantly changing in their intensity. Brighter, dimmer, to varying degrees. What you are seeing is the pulse rate affecting how much total light they give off. When the LEDs are stationary, your eyes detect the difference in total light delivered as brightness, but when spinning you can see the actual pulses as the dark gaps between the lines and dots in its rotation. Cool, huh?
So there's a lot of Christmas lights that are LEDs now, and I can tell them from the old ones instantly by their flicker. I was at a big Christmas light display with hundreds of thousands of these LED lights, and I about went nuts. Since these are AC, they always pulse at 60Hz. How to visualize that when they don't spin? I used my cell phone camera, and swung my arm quickly sideways while taking a picture of the lights. Can't rotate the lights, then rotate yourself. The result is below.
There's lots of reds in there, but only a few blues or greens. Count the number of blue dots captured from one of these lights, and you'll see that my cell phone camera captured six pulses. At 60 pulses per second, that means my camera caught 1/10th of the pulses delivered every second.... so now I know that my cell phone camera's exposure time is 1/10th of a second. Incidentally, there are a couple of white incandescents that got caught in there on the lower left, and you can see the intensity of one of them oscillating, though it never has enough time to go out between pulses, hence the pulses are invisible to the normal naked eye.
Cool huh?
Or boring.
I know it's late, but Merry Christmas!
100 years ago, many AC systems were operated at 25Hz (25 cycles per second), and pretty much anyone could detect it when looking at a light bulb. You could see it pulsing really fast. At today's 60Hz, it is pretty much impossible to detect that pulse in an incandescent light bulb, because the filament does not have enough time to noticeably dim between the 60-times-per-second pulses.
Unlike incandescents, fluorescent lights visibly pulse to some people whose eyes are sensitive enough. Like mine. I can see the flicker of computer monitors set to 60Hz, too. Both give me headaches. Many monitors have configurable frequency settings, so I change them to as high a setting as possible. If I can't, the monitor is disposed of.... somehow I usually find a way. And of course I avoid using fluorescent lights as much as possible.
But there's a relatively new flicker-detectable 60Hz light source out there, and I probably can't run away from it: Cheap LED lights.
LEDs are either ON or OFF. There is no 'warmup' or 'cooldown' interval.
Have you ever seen one of those spinning light gadgets sold at gift stores, with the LEDs on it? As they spin, the lights make various multi-colored solid lines or dashes or dots, rotating back or forward, and they are fabulous for mesmerizing cranky 2-year-olds for a few minutes.
Next time you get your hands on one of those, grab the spinner so it can't turn, and then turn the thing on. These are battery-operated, so they are not strictly 60Hz, but run at variable frequencies controlled by the internal circuitry. You'll note that, when the spinner is not spinning, the LEDs are constantly changing in their intensity. Brighter, dimmer, to varying degrees. What you are seeing is the pulse rate affecting how much total light they give off. When the LEDs are stationary, your eyes detect the difference in total light delivered as brightness, but when spinning you can see the actual pulses as the dark gaps between the lines and dots in its rotation. Cool, huh?
So there's a lot of Christmas lights that are LEDs now, and I can tell them from the old ones instantly by their flicker. I was at a big Christmas light display with hundreds of thousands of these LED lights, and I about went nuts. Since these are AC, they always pulse at 60Hz. How to visualize that when they don't spin? I used my cell phone camera, and swung my arm quickly sideways while taking a picture of the lights. Can't rotate the lights, then rotate yourself. The result is below.
There's lots of reds in there, but only a few blues or greens. Count the number of blue dots captured from one of these lights, and you'll see that my cell phone camera captured six pulses. At 60 pulses per second, that means my camera caught 1/10th of the pulses delivered every second.... so now I know that my cell phone camera's exposure time is 1/10th of a second. Incidentally, there are a couple of white incandescents that got caught in there on the lower left, and you can see the intensity of one of them oscillating, though it never has enough time to go out between pulses, hence the pulses are invisible to the normal naked eye.
Cool huh?
Or boring.
I know it's late, but Merry Christmas!
Friday, December 25, 2009
The Pre-Plan
Showed up for work at the power company this fine Christmas morning.
Keeping the lights and the heat on for you while you do whatever you do this holiday. Don't mention it. I get paid extra to be here and I am happy to have a job.
Anyway, for some reason, the refrigerator was replaced during my days off. Looks like the person in charge ordered a really nice stainless steel side-by-side to replace the old one. What was wrong with the old white enamel one is not clear. Apparently the boss simply wanted us to have a new one. With stainless steel.
They didn't go cheap. Bought a side-by-side to replace the old over/under. After all, we're a multi-billion $$$ company, so we can afford it.
If you've never compared refrigerators... typical mid-line over/unders are about 33" wide, while side-by-sides are rarely (if ever) less than 38" wide.
Yeah, you can see where this is going.
So in the corner of the control center kitchen, where the old fridge used to be, the new one is in front of the old hole, turned 90 degrees and against the side wall. Now we have the loss of space in the kitchen, the open and inaccessible hole blocked by the sideways fridge in front of it which will no doubt gather accidental trash and crud, and you know..... the new one has less fridge space than the old one overall, in exchange for a bigger freezer that we pretty much never use.
Not to mention, the all-important pizza box doesn't fit in a side-by-side.
Nice upgrade.
Pre-plan FAIL.
I'll keep you posted on what comes next: (A) Swap for smaller fridge (with or without consulting the guys who actually use it), (B) Spend a bundle to remodel a kitchen that does not need a remodel so that the wrong fridge will now fit, or (C) just leave the goofy situation as is.
Keeping the lights and the heat on for you while you do whatever you do this holiday. Don't mention it. I get paid extra to be here and I am happy to have a job.
Anyway, for some reason, the refrigerator was replaced during my days off. Looks like the person in charge ordered a really nice stainless steel side-by-side to replace the old one. What was wrong with the old white enamel one is not clear. Apparently the boss simply wanted us to have a new one. With stainless steel.
They didn't go cheap. Bought a side-by-side to replace the old over/under. After all, we're a multi-billion $$$ company, so we can afford it.
If you've never compared refrigerators... typical mid-line over/unders are about 33" wide, while side-by-sides are rarely (if ever) less than 38" wide.
Yeah, you can see where this is going.
So in the corner of the control center kitchen, where the old fridge used to be, the new one is in front of the old hole, turned 90 degrees and against the side wall. Now we have the loss of space in the kitchen, the open and inaccessible hole blocked by the sideways fridge in front of it which will no doubt gather accidental trash and crud, and you know..... the new one has less fridge space than the old one overall, in exchange for a bigger freezer that we pretty much never use.
Not to mention, the all-important pizza box doesn't fit in a side-by-side.
Nice upgrade.
Pre-plan FAIL.
I'll keep you posted on what comes next: (A) Swap for smaller fridge (with or without consulting the guys who actually use it), (B) Spend a bundle to remodel a kitchen that does not need a remodel so that the wrong fridge will now fit, or (C) just leave the goofy situation as is.
Saturday, December 19, 2009
Fuzzy Brain Radio Follies
(tones)
Engine 51, Engine 57, Mayberry Engine 13, Medic 98.... traffic accident.... tac channel is TAC2.
Ugh. Engine 51 is first-due. I look at the clock. 02:24. Ugh. OK, here we go.
The fuzz is heavy. I pull out in trusty 51 and grab the mic to come online.
Engine 51 is responding.
10-4 Engine 51.
I then hear a couple of other sort-of-nearby units from our agency start our way, ready to turn around if not needed.
Then I look at the radio. Oops... I used the FireMed channel.... but they answered me anyway and just went with it, without a poke. Thanks, guys.
I pick up the mic again to advise dispatch that I am cutting over to Mayberry's response channel to touch base with Engine 13 when they come up. You see, they don't have the fancy-schmancy 800MHz system we have, so on M/A someone has to go meet them on their channel.
As I key the mic, I abruptly realize that I never changed channels in the first place. I am still on FireMed instead of TAC2. Since I came online first, as first-due I am the one responsible to initiate the correction and make sure everyone is moved over to TAC2.
I have two messages in my fuzzy head, and I have already keyed the mic. (#1) I am going over to Mayberry Channel 4 for a moment. (#2) Let's move all responding units to TAC2.
My fuzzy brain, under pressure (mic is keyed), smashes these two messages violently together.
Dispatch from Engine 51, let's move all responding units to Mayberry Channel 4.
Oh crap, did I really just say that on the air?
I really fubar'd this. I can visualize every guy on a responding unit, as well as anyone else listening, staring at their radios as if they just channeled radio traffic from the Burger King drive-thru. Say what? You want us to... did he just say that?? Not all units responding even have the capability to go to Mayberry's channel.
And I'll be danged if the dispatcher didn't just go with that, too, nary skipping a beat.
10-4 Engine 51. All units responding on the traffic accident, move to Mayberry Channel 4 per Engine 51.
I wish he had put the brakes on and called me on the goof... but off we go before I can pipe up again to fix it.
So... some guys just follow orders and go to Mayberry Channel 4 as directed, some stay on FireMed to see what my next move is because they realize I am fuzzed up and should come out of it soon, while still others go to TAC2 as we were supposed to have done all along. Once I let the livestock out of the pasture, I wasn't sure how to get them corralled again. From there on out, it was a great big communications Charlie Foxtrot.
Thankfully it was a one-car, non-injury wreck, not a lot of coordination involved in finding units, whichever channel they went to, and telling them to cancel.
Lesson to self (and I rant about this to the new guys constantly): Engage brain and think over your message before you key the mic.
The Captain sat me in the office for a few minutes the next day, just to make sure I still knew the protocol for M/A and TAC channels. He knows it was 0-dark-30, but he had to check. I don't blame him.
Ugh.
Engine 51, Engine 57, Mayberry Engine 13, Medic 98.... traffic accident.... tac channel is TAC2.
Ugh. Engine 51 is first-due. I look at the clock. 02:24. Ugh. OK, here we go.
The fuzz is heavy. I pull out in trusty 51 and grab the mic to come online.
Engine 51 is responding.
10-4 Engine 51.
I then hear a couple of other sort-of-nearby units from our agency start our way, ready to turn around if not needed.
Then I look at the radio. Oops... I used the FireMed channel.... but they answered me anyway and just went with it, without a poke. Thanks, guys.
I pick up the mic again to advise dispatch that I am cutting over to Mayberry's response channel to touch base with Engine 13 when they come up. You see, they don't have the fancy-schmancy 800MHz system we have, so on M/A someone has to go meet them on their channel.
As I key the mic, I abruptly realize that I never changed channels in the first place. I am still on FireMed instead of TAC2. Since I came online first, as first-due I am the one responsible to initiate the correction and make sure everyone is moved over to TAC2.
I have two messages in my fuzzy head, and I have already keyed the mic. (#1) I am going over to Mayberry Channel 4 for a moment. (#2) Let's move all responding units to TAC2.
My fuzzy brain, under pressure (mic is keyed), smashes these two messages violently together.
Dispatch from Engine 51, let's move all responding units to Mayberry Channel 4.
Oh crap, did I really just say that on the air?
I really fubar'd this. I can visualize every guy on a responding unit, as well as anyone else listening, staring at their radios as if they just channeled radio traffic from the Burger King drive-thru. Say what? You want us to... did he just say that?? Not all units responding even have the capability to go to Mayberry's channel.
And I'll be danged if the dispatcher didn't just go with that, too, nary skipping a beat.
10-4 Engine 51. All units responding on the traffic accident, move to Mayberry Channel 4 per Engine 51.
I wish he had put the brakes on and called me on the goof... but off we go before I can pipe up again to fix it.
So... some guys just follow orders and go to Mayberry Channel 4 as directed, some stay on FireMed to see what my next move is because they realize I am fuzzed up and should come out of it soon, while still others go to TAC2 as we were supposed to have done all along. Once I let the livestock out of the pasture, I wasn't sure how to get them corralled again. From there on out, it was a great big communications Charlie Foxtrot.
Thankfully it was a one-car, non-injury wreck, not a lot of coordination involved in finding units, whichever channel they went to, and telling them to cancel.
Lesson to self (and I rant about this to the new guys constantly): Engage brain and think over your message before you key the mic.
The Captain sat me in the office for a few minutes the next day, just to make sure I still knew the protocol for M/A and TAC channels. He knows it was 0-dark-30, but he had to check. I don't blame him.
Ugh.
Tuesday, December 15, 2009
Commentary on Death by Ignorance, and System Protection
There's a little tie-in commentary I want to make in regard to the previous post and all of the system protection stuff talked about in the last two tutorials.
Everything in a substation is protected by zones, so why in the world would the carnage depicted in the photos on the last post be so severe? Why didn't something detect the fault and clear it before it got so bad?
Well, my friends, what probably happened in that case and does happen in many others like it, is that technically there was never a fault. There was never a hard connection to the fatal arc from the generator-to-component chain that is watched by fuses and relays.
Part of the transmission of electricity involves a powerful electromagnetic field which literally rotates around energized equipment and power lines, out to a distance of several yards, though the strength of this field weakens quickly as the distance from the energized equipment increases.
You hear about people complaining about EMF exposure when living near power lines, so you can imagine the distances the fields can reach out to. And then you can imagine the fields you're immersed in when you're in a substation and fairly close to the big stuff. Induction potential is normally negated on the structures and fences at stations by the grounding straps which dissipate the potential immediately
If the induction potential is not dissipated by grounds (because some Darwin Award candidate removed them), any electromagnetic induction potential will look for a way out, and will create an arc when it finds it. Since it draws no actual fault current from the energized equipment, there is nothing for the relays to detect. It will just burn and burn and burn, either until (1) there's nothing left to burn, (2) the damage created by the arc grows so large that the arc can no longer jump the gap, (3) the arc reaches energized equipment where the relays can see it, (4) the damage causes a structural failure of some variety that indirectly creates a real fault, or (5) a power company guy observes the arc and takes action to de-energize the associated equipment.
So, as you might conclude, exposure to electricity by induction is far more hazardous than exposure to straight-up energized equipment. The energized stuff will pretty much kill you 99.999% of the time, though rare exceptions have been noted and made possible by quick fault clearing and only on relatively low voltages. But you've got no chance at all when you get whacked by undetectable and non-clearing induction current.
Just some things to think about.
Everything in a substation is protected by zones, so why in the world would the carnage depicted in the photos on the last post be so severe? Why didn't something detect the fault and clear it before it got so bad?
Well, my friends, what probably happened in that case and does happen in many others like it, is that technically there was never a fault. There was never a hard connection to the fatal arc from the generator-to-component chain that is watched by fuses and relays.
Part of the transmission of electricity involves a powerful electromagnetic field which literally rotates around energized equipment and power lines, out to a distance of several yards, though the strength of this field weakens quickly as the distance from the energized equipment increases.
You hear about people complaining about EMF exposure when living near power lines, so you can imagine the distances the fields can reach out to. And then you can imagine the fields you're immersed in when you're in a substation and fairly close to the big stuff. Induction potential is normally negated on the structures and fences at stations by the grounding straps which dissipate the potential immediately
If the induction potential is not dissipated by grounds (because some Darwin Award candidate removed them), any electromagnetic induction potential will look for a way out, and will create an arc when it finds it. Since it draws no actual fault current from the energized equipment, there is nothing for the relays to detect. It will just burn and burn and burn, either until (1) there's nothing left to burn, (2) the damage created by the arc grows so large that the arc can no longer jump the gap, (3) the arc reaches energized equipment where the relays can see it, (4) the damage causes a structural failure of some variety that indirectly creates a real fault, or (5) a power company guy observes the arc and takes action to de-energize the associated equipment.
So, as you might conclude, exposure to electricity by induction is far more hazardous than exposure to straight-up energized equipment. The energized stuff will pretty much kill you 99.999% of the time, though rare exceptions have been noted and made possible by quick fault clearing and only on relatively low voltages. But you've got no chance at all when you get whacked by undetectable and non-clearing induction current.
Just some things to think about.
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