Changing a "Smart meter" - 3 phase
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- Опубликовано: 14 окт 2024
- I don't go very in depth on metering in this video... just kinda covering the "Lineman" side of things.
Most Importantly
Make sure you have the proper meter.
-Never leave an open circuit on an energized "CT" (current transformer).
Lastly, I mention that you can't meter high voltage... you kinda can, but it's not practical. Any common high voltage meters (which many exist), use resistors, PT's or Ct's to reduce the values at the metering element.
Cheers all!
Be safe! 🍻👊
I'll try a technical explanation of why you can't open the secondary of a CT. The ideal operation is that it will force the proper secondary current: if it's 100 to 5 and you have 100 amps in the primary, it's going to do its darndest to force 5 A out of the secondary wires. Even if that requires a high voltage. And that high voltage can produce an arc, or break down insulation that was never designed to handle substantial voltage.
The high voltage will also drive extra flux through the magnetic core and saturate it, which leads to spiky non-sinusoidal waveforms that can have even higher peak voltages, and can even mess with the power quality flowing to the load on the primary side.
I also want to say that as an engineer and an engineering professor, I have learned a tremendous amount from this channel. Reminds me of when I first started as an engineer and was lucky enough to get paired with a very smart and experienced technician, who taught me lots of valuable skills.
And is it the same for donut CTs?
In my mind, the answer is NO. But asking just to be sure.
Also of interest: In electronics that need very high voltage, like CRT tubes, this effect is used in special transformers called flyback transformers to generate the high voltage.
@@martf1061 It is the same for donut CTs if they don't have an internal burden resistor.
@@martf1061 Same problem in donut CTs. Generally, if they're smaller, the problem will be less severe, and some have built in burden resistors so they are never truly open on the secondary.
All CTs are a coil of wire. In a donut CT, the coil is hollow and you slide the conductor you want to measure through the middle. In a bar type CT, a short conductor is already placed in the middle and you connect to each end. You can remove a bar type CT by disconnecting the lugs. To replace a donut CT, you have to cut the wire in order to slide it out. Bars are convenient, but a donut is tamper-evident because the cut and then spliced wire is noticeable. Because a CT is a current transformer, it can only read alternating current. Hall effect sensors are used to read direct current. Shunts can read either, but are more commonly used for DC because CTs are superior for AC in most cases.
The explanation given for why you don't want open lines on a CT is good. I'll just add that the term used is open circuit voltage or VOC, in case anyone is looking at equipment and sees it - photovoltaic solar panels are an example of where it is commonly seen, although the difference between the operating and open circuit voltages is not as extreme as it is for a CT. You usually don't see it as a listed rating on batteries, but you can stick a voltmeter on a battery and then add a load and see the drop when it switches from open circuit to operating a load. The counterpart is short circuit current, which is typically higher than operating current.
When I was in the industry (retired now) a very early teacher told us “ Electricity is a natural phenomenon of which to this day mankind does not completely understand.” …. I was instantly hooked, knowing I will learn every day and never be bored.
Still true today.
I'm an HVAC technician and I still need to know a lot of electrical work and still learning
If you deal with electricity with the understanding that it will kill you and that Job One is not allowing that to happen you'll do fine.
Rule One: Lockout, tag out, tryout. Verify again before beginning work.
Rule Two: Be a skeptic with electric. Trust nothing and no one.
I was taught in AIT after basic training in my electronics MOS that electronics is still theoretical.
My father said, "Electricity is the closest thing to magic that there is"
I don't go very in depth on metering in this video... just kinda covering the "Lineman" side of things.
Most Importantly
- Make sure you have the proper meter.
-Never leave an open circuit on an energized "CT" (current transformer).
Lastly, I mention that you can't meter high voltage... you kinda can, but it's not practical. Any common high voltage meters (which many exist), use resistors, PT's or Ct's to reduce the values at the metering element.
Cheers all!
Be safe! 🍻👊
Very interesting regardless
The difference with primary metering is that the customer gets to pay for the power loss in the stepdown transformer. I was the design engineer for a manufacturing plant that had four 2.5 MVA padmounts with a single primary meter. I enjoy your videos.
You have my curiosity - what scale of power loss do you see in this kind of setup?
@@curtw8827 This isn't factual. The vars are still being delivered and not recorded as watts. That's why we do 4 quadrant metering now.
@@Meowth849 All the heat generated in the stepdown transformer is watts, the customer is paying for them due to the primary metering. The customer may also be paying for powerfactor (vars). If the metering was on the low voltage terminals (typical), the customer is not paying for losses in the transformer since they are ahead of a secondary meter. My manufacturing plant has power factor correction equipment to minimize vars through the primary metering to the site.
@@curtw8827 VARs are what is used to magnetize a transformer coil, but yes. If it's primary metered this would be recorded and billed assuming a 4 quadrant meter or in the case of only delivered power. I'm not sure what I was thinking - I guess not primary.
From the very first time my dad explained to me the purpose of a screw-in fuse in our 100A residential fuse box in the basement, until I owned my first house, I have been fascinated with electricity and making sure I and others were safe around all things electrical. Now 63 years later, I marvel at your work and our local linemen who bring the power, especially after storms. You have my gratitude and prayers.
A HV primary metering tank is really nice for property security & power company employee safety. There’s only so many safety protocols/procedures you can be ready for and trained on in advance. Staying out of industrial property lets the power company set safety standards to keep their employees safe. Even excessive noise and vibration can be health & safety concerns.
I always hate entering RF sites for data/comms handoff. I’m always happy when I can place my handoff outside of the main comms hut.
In Germany every (most)costumer has a 3 phase 400 Volt and 63 ampere. Use a costumer more than 80 amps, they use the same technique to metering like this video.
But the transformer are more central and the wirering are underground. The hole neigborhood use the same transformer.
The wires get in the last 40 ore 50 years from overhead to undergrund. Only 13kv and more are overhead lines.
I appreciate your content. Greets from Berlin/ Germany.
Same in Sweden, you just basically never see overhead unless it's high voltage distribution lines.
We do have 230/400V overhead lines in Germany, but only in rural areas or older buildings, where changing to underground cable would be to expensive.
@@thebamplayer Yeah, we do too of course. But the norm is definitely underground.
Residential is typically 3 phase 400v??
@@petermuller161 Yes, unless it's very old. Older apartments with gas are often only given one phase with 230 volts.
The danger of opening a CT secondary when the primary is energized comes from the inverse relationship between voltage and current in any transformer. In this case, you only have the 5 amperes of current in each loop when the loop is closed, but break the loop and you now have the CT working as a step-up transformer. When working on the current loop side, you actually want to pull the right-hand lever of each pair first and close it last. I grimaced when you just went left to right like that when getting ready to swap the meter...
Interresting stuff .
Thanks.
Hi Aaron! About 52 years ago I received a BSEE degree from Newark College of Engineering (now New Jersey Institute of Technology). I worked in the communications business my whole career and started as an "Outside Plant Engineer" with NJ Bell so I never looked too far above the bottom 20 ft on the pole. LOL. I got a pretty good education on the theoretical side of power systems but never any hands on practical experience. I am totally hooked on your channel and can't thank you enough for sharing your real world experiences with us. I feel like I've learned more from you than I did in any EE course I took in college. Please stay safe and keep the episodes coming!
That's my alma mater! Half as many years ago though. Still a great school!
It sure is still a great school. I was there a couple years ago and almost didn't recognize the place. Ton of new construction. I forgot to mention to Aaron that I was captain of the NCE hockey team. We probably would have had a hard time beating his son's team but had a great time playing around the NY-NJ metro area. 5 am practices at the outdoor rink at Branch Brook Park were particularly enjoyable!
I am a homeowner that has become fascinated with electricity, and the grid, even more so now that I have solar with battery. I know the dangers but just trying to understand the grid and how it all works is my fascination. My mind wants to understand it and I love your channel as you are showing me things I don't think I would have been able to learn otherwise. I do know not to try and do anything you are doing.
As a meter technician, I've had to correct some linemen mistakes like shunted CTs and reverse current flow on one phase. Needless to say, they can be some high dollar mistakes if improper metering carries on too long. Good stuff, Aaron.
One small mistake can definitely cost a lot !!
Where mistakes are so costly,
We always have a second guy verify work when doing a full meter job (Pt/CT/test switch and meter).
Who pays the mistakes? The billionaires that own the companies that are already overcharging the masses? No harm there. But I'm sure it's the opposite by design. Wonderful world huh.
@@TheTubejunky Electric rates are set by officials appointed by elected office holders, the people you put in office to do so. You have put into office people to gouge you, if the rate is gouging. If the rate is higher due to some inevitable mistakes by employees, that is the cost of having electricity. That cost doesn't go away in government owned operations.
Power companies are generally owned by huge numbers of stockholders, not especially billionaires, and mostly indirectly through the funding of pensions. In any case, billionaires are calculated as such by the assets (stock) they own, not the money they spend on themselves. Those billions in assets remain locked into the operation as long as the operation exists, and remain so when owned by government.
@@TheTubejunkyIn our cooperative membership service agreement, we will recoup from or credit to the member(customer). The utility needs to have multiple check for errors like this. Glad to hear that Aaron’s got em and I have implemented prevention measures at my company too. IOUs and Municipals policies may vary and would be subject to local laws.
@@TheTubejunky Yes, you have to pay for the power you consumed. I'm not sure why you find that egregious but go off.
Had a New Smart Electric Meter installed about a year ago. Took Contractor longer to get out of truck and Open Box then to Pull the Old and Push On the New. 👍🙏
After 25 years in So Cal as an FSR, retired, I sure would like to have been watching your vids back then. In those days you really needed to press for info like you show, alot because on safety but, a guy didn't want to invest his knowledge unless you were serious. Thanks for what you do
9:32 - very well pointed out, the reason you cant leave a CT secondary open, is because of the magnetic flux that will be induced within the CT! It causes a spike in voltage and can surpase the ratings for any of the CT bushing insulation causing an arc. Keep the awesome videos coming!
It's my understanding is that when not connected to the metering device, a CT secondary should be shorted. Otherwise, high voltage "spikes" can be generated. The power to do damage is limited to the saturation of the iron in the CT. Of course, a simple reversed diodes in parallel will make the shorting automatic and that might be built into the pole mounted CT.
CT’s generate current which is converted to voltage by a burden resistor. V=IR so greater resistance (more ohms) means more volts. Open circuit (infinite ohms) = danger danger danger
The peak demand metering is also used as a billing factor of the total power usage for the Billing period. Thanks for all the videos posted.
The other reason you need a PT is because the current isn't necessarily in phase with the voltage, nor is it necessarily a pure sine wave. In order for the meter to record real power, power factor etc. accurately it needs to measure the instantaneous current and voltage on each phase thousands of times per second. It sounds difficult but there are specialized metering DSP chips that do the measurement internally so the main processor just has to tally up the total usage and report it.
The only purpose of a PT is to step down voltage. I have no clue what you are trying to say but it's probably wrong.
I love seeing how other countries / companies do things. That is neat trick of using a shorting switch before removing the meter, so as to prevent a high voltage on the current transformer secondary. Occasionally we would get trainees and the rare apprentice for a week long visit for the experience and to 'assist', in the lab I was in. They were mortified when we kept shorting out the secondaries of current transformers (we could push through up to 2,000A on the primary). I had a small current transformer that was junk, but would always put on a good show, place it in the HiPot cage make the wires on the secondary about 15mm appart pass through a couple of amps on the primary and watch the sparks. I don't know how they were installed out in the field, but we used to get a number of current transformers back from the field with damaged insulation.
Great video, Thanks.
It's great to see you posting again. I was an electrician with the USMC and we were trained to climb poles and deal with it. If we started falling from a pole we were trained to push away and hope for the best at the bottom . I hope you have all your family issues solved and you can start posting regularly again. Your videos are the best.!!!!!
I very much appreciate what you share. My rural home is supplied from a single transformer on a pole and your videos have helped me understand the technology. Thanks for the video.
Appreciate you linemen. We just went through a hurricane with plenty of power outages. Over 2.3 million customers right after the storm. Almost a week later and still 300,000 still without power. Quite a job.
You nailed it with not wanting to open CTs when they're live. I've seen the aftermath form some medium voltage stuff blowing. It's less that the current jumps up when you open them and more that inductive loads don't like changing how much current passes through them. So if you had 5A going through and you change the path from a copper wire to a few inches of open air the voltage can spike and either draw an arc at the switch or break down the insulation and energize the secondary side.
I really like all your videos. They're one of a kind and very educational . Thanks for taking time out to do these. I'm sure many people would agree. Thanks
I remember checking this channel years and years ago first like "Oooh this is all new and interesting" then as I have gone forward in both studies and experience the videos feel like the sort of conversations I have with colleagues on the job when we have 10 minutes to spare and it turns into story time
For large electric users ( like a steel plant ) I always picture a old glass mechanical meter the size of a 20 ft round swimming pool with the disc furiously spinning around. . .
I love watching your videos. I’m retired HVACR technician of forty seven years. When I first went to school to learn my trade one of the first things my instructor taught us was to never be afraid of electricity because it will get you injured or killed. Just always respect it and I never forgot that and I’m still alive today.
I came across a pile of PT's while wondering around the local utility's yard and was so curious why conduit with low voltage wireing was going up to a medium voltage head. This explains it perfectly, thank you!
I appreciate you sharing your story. You have not idea how you have helped me. Thank you!
Rebuilt a metering tank (as you call it) for a local mill & another 1 for a golf course. 14,400 through & 110/220 out for the meter. 255 litres of Voltesso oil in it & it dripped for days. The phenolic plate for the meter connection had burnt through & need replacing. Hooked it backwards to test with a surge tester & made some awesome plasma balls with welding rods for arc points.
Just wanted to say I'm another recent subscriber who randomly found your channel. I can't stop watching your videos because they're super informative! I don't work in the electrical trade, but I'm always trying to learn how the world around me works
Awesome stuff Aaron we're just getting over a heat wave here in Las Vegas over 5 days above 115 one day couple days 120 deg, power is very important Hope your day is going well
I absolutely enjoy your videos. I respect those power line from a distance.
This was great I always wondered how the large scale metering worked!
Thanks for your video Aaron on primary metering. Excellent explanation on Ct's , Pt's, and all associated wiring.
thanks for sharing this was very insightful, I am working towards becoming a lineman.
Interesting set up to meter a 3 phase service.
I am actually enjoying your channel. I happen to run across it and I think it’s very interesting. I had some family members. Of course I’ve passed on now but used to work for our local power company. In fact, one of the members of my family was a head lineman, so it’s quite interesting seeing what you’re doing
Looks like some meters we use in the US as well. Some buildings I worked at had different 3 phase meter. some of the 480V service ones have dual displays . the second display is demand . I seen 208V 3 phase with that same type meter .just different brand . the old meter had the dials and the 480V one had 2 sets of dials . I was working at time of meter change to see the newer meter go in.
Neat stuff. I always wondered how they meter those multi-megawatt installations without melting the meter.
What’s up Arron? Hope things are still going great but I had to laugh when I heard “clear as mud” reminds me of high school, my science teacher always said that & now I catch myself saying it every so after and people just glance at me me.. lol.. but the video was great & as always very educational, I’m very very familiar with the setup here in North America but still watch to learn because none of us know it all, & I’m glad you are willing to share.. hope you and the family is doing well👍
Great explanation on metering and associated replacement, find your videos informative, thanks!
The way you explained seems that the ratio of the transformers can be tuned on the unit. As they are probably hard to inspect, how do you guarantee that the customer doesn’t mess with the CT ratio directly on the transformer in order to pay less for electricity?
Thanks for the videos! As an electrical engineer that doesn’t work with high voltage, I learn a lot from them.
from what i remember from school in January, open circuit on a ct will cause the voltage (or amps) to reach a dangerous level because its no longer grounded or something but all i remember is my instructor saying if there ever was a question that should get you failed instantly is saying "yes, open circuit on a ct is ok"
I have always liked the description of Primary rate metering is that metering is simple " Sampling transformers step down the Voltage and the Current down to a level a self contained meter can read on all three phases of power. This metering can be set up for overhead to underground lines like you show in the video. Or Overhead primary to overhead customer owned system. The metering for the customer owned system would be the same. The size of the metering transformers would be based on the customers expected load. Great video.
Bro, you are a rock star! Your knowledge is impressive.
Always interesting seeing the wire colours other countries use. Here (New Zealand) three phase is also red, yellow and blue, but neutral is always black. Single phase is red and black. Most appliances though have the European colours (brown and blue), so another set of colours to remember. Not sure how we do industrial metering like in the video, the only three phase meter I’ve seen was wired similarly to a residential meter (inline) as it was essentially a retail store, so no heavy loads except for a roller door. I believe the door was the only three-phase circuit, everything else was divided evenly across each phase.
And, of course, here in the States, the colors are Black-Red-Blue or Black-Orange[high-leg]-Blue. Or Purple-Orange-Yellow. Neutrals are white or grey. Ground(ing)s are always green, green/yellow-stripe, or bare.
Nice work Aaron, I like the color code you guys use. I've been pushing my company to use a similar color code. One thing I do is mark phase rotation in all my 3 phase meter boxes. Knowing the rotation comes in handy during transformer changes and storm restoration.
The reason can't you open circuit a current transformer (CT), but you can open circuit a power is transformer is because a power transformer has winding on the primary side and CT does not (just a wire which is a single loop). As a result, the CT has an intern resistance that is very high, the power transformer has an internal resistance that is very low. From Ohms law V=IxR, so if the current is significant enough and the internal resistance is high - high current x high resistance = high voltage. A CT may see 400V or 800V or more. From Bobsdecline video, the CT test switch separates the currents by a very small distance (1/8"-1/16", 2mm or less). High voltages will begin arcing in very short distances, arc causes damage. Shorting the CT provides a low resistance, low resistance X high current = lower voltage.
Now that was cool, it really is Rocket Science. Metering High Voltage with lower voltage, who knew.
Thanks Aaron, that was really instructive. Stay safe.
Howdy Aaron. Always enjoy your content as I find your particular world very interesting. Keep up the good work and stay safe! Oh... got a question for ya... why the name of "Bobsdecline"?
Power systems engineer here, spent a good chunk of my career teaching. HMU if you want to go through the theory of why you short circuit CTs and why they make high voltage sometime. It could be a really good video on it's own.
I'm not any kind of electrician or lineman. But, can still learn something. 🤝 🍻
In a short circuit the voltage is close to zero. The CT is a transformer with a winding ratio with current in mind. The meter's relatively low resistance shunts the voltage close to zero. It is the current in the circuit that is measured. With the CT open ,not connected to the meter's low resistance, you have the potential of the winding ratio of the CT on the high line.
Hey Aaron, I came across a coax drop today that was melted nearly the WHOLE length from the house to the tap (fairly long with a midspan) Customer said it was smoking yesterday! Since we aren't supplied amp clamps, I was concerned it was a serious problem, so I called MB Hydro to be safe.
A guy showed up maybe 20 min later with a bucket truck, but didn't seem too concerned. He pulled the meter, ran some tests and said everything's showing good. I felt really dumb cuz I fully expected for him to find an open neutral! I then asked if I could cut down the melted drop from the house while he was there, just in case. Nothing. No sparks etc.
He changed the crimp on the neutral at the weatherhead just to "do something" and trimmed some large branches near the pole after talking to another neighbour.
Anyway, he said he'd hang around while I changed the drop. I asked if his tests would indicate an issue with the neutral from the panel to the meter, and he said no, that's not his problem (understandable.)
Their internet came back up, so I asked them to try their oven and dryer for a few min. I also said if the drop melts again to call an electrician. I was so worried that cutting the old drop could've started a fire.
The troubleman said he's seen some strange things with open neutrals but not a drop melted that bad.
Sorry for the long message. Just curious what your thoughts are, and hopefully we get to see a video on this topic soon. Thanks!
Oven and dryer are balanced loads so they wouldn't cause any neutral heating. The best test (assuming you don't know anything about the customer's wiring) is _one_ high load plug-in appliance like a microwave or space heater, that way you can be sure it is 100% unbalanced.
Awesome explanation! Thank you
The CT has the inverse winding ratio of a PT or other voltage transformer. So a single winding on the "primary" and multiple windings on the secondary. If the secondary isn't shorted or otherwise loaded in an energized situation, a very high secondary open circuit voltage will be created resulting in a shock hazard or potential equipment damage. (At least that is the explanation we got in the metering section of electrician apprenticeship.)
10:30 so THAT is why the boss had me to flip all of the switches in the box outside at 12:30 am, he said it shut off the windows 95 computer running the business,
joking!!
Lol
I find this stuff very interesting, so thanks for this content
Thank you for another great video.
Good info from Germantown Wisconsin
My understanding is smart meters have a built in cell phone. Driving around you will notice some transmission towers have cell antennas mounted on the sides. Some substations also have cell antennas. Your meter reports to the nearest substation or transmission tower. This is how the power company knows instantly when your neighborhood has a power outage. They also know which circuits are out and can instantly reroute power around the outage. I remember the old days not too long ago when customers had to report power outages themselves. Then wait while the crew drove around looking for the problem.
Maybe some do. The ones in our area use 915-930 MHz ISM band, spread spectrum. Yes, there's receivers on poles every so often. Often the system is not what would be described by security pros as secure.
Linemen are underpaid...they keep everything going....and it is everything
Those transmission towers with cell equipment are not usually for the utility company's use. In most cases is just a good location for cell equipment placement so think of it as "shared space" instead of another tower being erected. BTW, that shared space is actually a rental, which means the cell providers are paying to use that location.
Our meters are RF in the old pager frequency band. We have antennas on radio towers that communicate two ways. It’s a remarkable system that informs us of readings and outages in real time.
Just FYI, for your safety. In this video you did open circuit the secondary of the CT for a short time. You should always open your shunts (polarity - the ones that catch and short to neutral) before your returns. By opening the returns first your polarity has no return path until you opened the next switch in line shorting it to neutral.
Yes that's correct 🤦♂️
@@Bobsdecline Stay safe brother
Interesting information
Aaron you know more about electricity than our new generation of electrical engineers......😂😂😂😂😂 Keep up the amazing work!!!!!🙏🙏🙏🙏🙏
His name is Aaron (watch some of his other videos where he tells you how this name was created). He is certainly at the top of his game, it's clear he loves what he does and is a master of it with dedication. I have been watching his back catalogue and every so often he will say something in passing and I'm, hang on a minute that is way above your paygrade. I'm in awe of what he does, I have worked with many linemen and they do a fraction of what Aaron does and they did it poorly, frequently having to get them to fix their work.
This stuff is so dangerous and that is without the frozen poles and heights he works at.
He is an amazing advertisement for kids trying to work out what they want to do.
@@jumper123910 thanks man..... Yes Aaron is on top of his game.... 😀😀😀😀😀😀😀😀😀😀
6:37 you can see the CT is a multi ratio either 100 or 200/5. Those are chosen based upon the taps used on the secondary side of the ct ie x1-x3 or x2-x3.
It's not muddy, but it's a bit foggy for someone like me. I can now understand the different applications for three phase metering. Larger businesses and farms could have different meter options. Thanks for the info. Stay safe, and God bless
Thanks Arron 👍👍👍
Excellent info. Thanks for posting! What is the volts rating on those gloves that you are using and how often do you retire them for a new pair?
That is basically how we meter the two 13.8kV feeders into where I work, only difference is the CTs and PTs are mounted in the main switchboard..
Hi Aaron,
I sent your hearing protection to you by UPS ground. Not sure when it will arrive? Keep an eye out for it.
Great video! We have a separate metering department. We don't have any training on it. Thanks for the tutorial though. We have those overhead metering units for very large customers only.
I thought I noticed a hole in your left "keeper" or gauntlet? Better check that out. I don't want your rubber glove to get a hole too. I know you check your rubber gloves & sleeves daily 😉.
Keep up the great content! I hope everything is alright? Thinking of you & your family.
My relative has a house with 3 phase power. 3 600 amp breaker panels and enough Air conditioning to keep the house cool, and in SC it is over 100 degrees 6 months out of the year
The electric bill is 4000 a month
What model of phone have you got? The zoom is great.
Great video, thanks
greetings brother lineman from flagstaff Arizona 👊 🇺🇸
I wonder if the disconnection causing an arc thing is because the CT is basically an inductor, which is something where if the power is pulled off, the voltage spikes. You use diodes (I think?) across the inductor to clamp the voltage spike.
Regarding the current transformer, if it is essentially an AC current source representative of the customer load by some fraction, then it is designed to be connected to a very low impedance, as in the power meter. With any current source, the output voltage equals current times resistance. An open circuit has very large resistance, so the output voltage will also become very large. The open-circuit voltage will rise until it arcs over, or finds some other path through parasitic capacitance in the transformer windings, for example. Whereas voltage sources don't like short-circuits, current sources don't like open circuits. I'm not familiar with CTs, as such, but the electrical theory should be the same. Please correct me if I missed something!
An open secondary on a CT will cause it to produce a very high voltage, usually high enough to damage the CT and high enough to be a serious hazard.
CT without a Burden (AKA the meter ) will produce a high voltage across it . And can arc through the windings of the CT and destroy it .
Aaron, can you cover Ferroresonance in one of your videos and if you have ever ran into it? I know you can isolate the meter by opening the cutouts, but was curious if ferro could be an issue on a tapline like this.
Seeing that meter, all I could think was Marathon Man: "Is it safe?"
I wonder if ‘safe’ on the meter is the built-in diagnostics detecting a problem and going into a safe mode.
Unhooking a CT leads will turn it into a fly back transformer and create very very high voltage, 10000s of volts
Love the channel!!
Those wing nuts could have fallen down across those HRC fuses to the left, when you undid them. Those HRC fuses need a plastic cover to stop that happening.
I'm sure you get this question all the time: Are the new digital/WiFi-connected smart meters more "efficient" at detecting residential usage, say by compensating in real time for different Power Factor values? I know a guy who used to keep his bill artificially (hence, illegally) low by adding capacitors to his home's wiring.
And, if the answer is essentially "Yes", do you give any credence to consumers yelling about their bills going "Up", "Way Up", even "2-3x Higher" after the upgrade??
I'm curious how a smart meter can communicate outside that metal enclosure? I mean, yeah it's not a perfect seal and some RF will sneak past the door gap but there's still a ton of attenuation there.
Love the videos man
Hi Aaron years ago I had a friend who had a old retired electric meter and he made a table lamp out of it. I thought it was neat to have a meter connected to a table lamp. I was wondering if I could make one with a smart meter?
As long as the internal copper or aluminum carrying conductors are intact, it will work. Some smart meters will have an internal switch though, and if that switch is open, then you would need to close that connection. My old boss had a lamp like you describe and it’s cooler to see the old disc spin, imo
There isn't really any difference between a current transformer and a voltage transformer, its just the way that they are used. A current transformer is just one that has a very low resistance burden connected across its secondary winding and it usually has a very high turns ratio. The primary might have say one turn and the secondary 1000 turns. In normal use the low burden resistor allows sufficient secondary current to flow to cancel the primary current with only a small voltage across it and an even smaller voltage is reflected to the primary. So the presence of the CT has negligible effect on the load circuit. If the secondary circuit is opened then it ceases to be a CT and becomes a voltage transformer and just like any other voltage transformer it will try to generate a secondary voltage that is the turns ratio times the primary voltage. So in this case if the primary is say 7kV then it will try to produce a secondary voltage of 7,000kV. This is sub optimal.
Bring the spinny wheel back on meters
Are these big consumers pay for the 1 power factor, so is it corrected inside the meter or do they have to use additional equipment to balance out the power factor to get the real consumption?
Just wanted to pass on to you that there cartridge fuse covers in stores that covers those fuses and holder so you don’t drop something across it and cause a short.Made of plastic and clips on. All new installation should have them.
Do those industrial customers also get billed for apparent power?
In most places where smart meters are used, there's a charge on the bill for peak power usage.
In commercial installations they make a lot of sense, remote metering and being able to analyse demand, peak, off-peak etc really helps.
But in residential I think they are a moneygrab.
In my City they rolled out digital meters basically only because they want to replace old analog meters since they cant guarantee their safety and accuracy after 30 odd years in service.
They say smart meters aren't really worth it for them since they are more expensive and don't provide much benefit to the local grid operator since they already have good metering at every sub and local feeder.
Good deal Aaron.......
I watch these.. and go "damn I really should switch fields" but I cannot afford to apprenticeship for $18/hr again. Guess i'll stick with automotive...
FYI if the red and black tape was supposed to block the # you can clearly see on other angles
U stay SAFE ~~~~~~~~~
the wires for that meter look on the small side for a big building like that or does the site have multiple meters on it?
The current doesn't go through the meter directly. Current goes through current transformers, in this particular building they have a 100:5 ratio. If the building is drawing 100 amps the CT steps it down to 5 amps which the thin wires can easily handle.
you forgot to screw the Plexiglas cover wing nuts back on :)