Hi friends. is any way to detecting the Di/Dt with OP AMP under the 20Kv power line ? I want when the power line current increased 120 amp or decreased 120 amp the OP AMP output be activated.
thanks.
So what are you using as the sensor? Its kV, not Kv, note, which is the electric motor velocity constant normally.Motor constants - Wikipedia
20kV will instantly kill, so I presume you are expecting to detect the remote magnetic fields? Power lines
carry no net current when operating properly so that the magnetic fields will cancel fairly efficiently except
for earth leakage currents which will pose a problem as you'll be likely to be measuring the wrong thing.
The magnetic fields at say 3m from 120A current (even when not cancelled) are not big, 8µT in fact (the Earth's
field is around 20 to 60µT depending where you are).
However changing fields are easy to sense with a magnetic loop antenna. The loop's axis needs to be
perpendicular to wire and horizontal. Pickup voltage with a loop of radius r and N turns is BwNπr^2
where B is the field and w the angular frequency of the mains (2πf).
But as I said the currents normall sum to zero in a power transmission line (as its 3-phase).
No idea why you are fixated on opamps.
MarkT:
So what are you using as the sensor? Its kV, not Kv, note, which is the electric motor velocity constant normally.Motor constants - Wikipedia20kV will instantly kill, so I presume you are expecting to detect the remote magnetic fields? Power lines
carry no net current when operating properly so that the magnetic fields will cancel fairly efficiently except
for earth leakage currents which will pose a problem as you'll be likely to be measuring the wrong thing.The magnetic fields at say 3m from 120A current (even when not cancelled) are not big, 8µT in fact (the Earth's
field is around 20 to 60µT depending where you are).However changing fields are easy to sense with a magnetic loop antenna. The loop's axis needs to be
perpendicular to wire and horizontal. Pickup voltage with a loop of radius r and N turns is BwNπr^2
where B is the field and w the angular frequency of the mains (2πf).But as I said the currents normall sum to zero in a power transmission line (as its 3-phase).
No idea why you are fixated on opamps.
thanks for reply. I want to build a overhead power line fault indicator device. when the power line Di changes, the OP AMP should waking up the MCU and sending SMS.
MarkT:
so I presume you are expecting to detect the remote magnetic fields?
Yes, it is installed on the line by the device we make.
MarkT:
The magnetic fields at say 3m from 120A current (even when not cancelled) are not big, 8µT in fact (the Earth's
field is around 20 to 60µT depending where you are).
The distance from our device to the line is only a few centimeters. That is, the device is connected to the line.
MarkT:
However changing fields are easy to sense with a magnetic loop antenna.
But I don't know how much coil winding is. how to calculating ?
thanks.
any help ?
Connected to the line? No, this is not a job for an Arduino, or any low voltage electronics come to that.
ErfanDL:
Yes, it is installed on the line by the device we make.
You make a commercial product for use in a highly dangerous situation and are asking amateurs for advice?
(And I include myself in the amateur category, with over 40 years experience in analogue/digital electronics including RF, microwave and some safety, high voltage and high current applications)
I remember the SAME question on a post from several years ago. Possibly from the same person.
Paul
MarkT:
Connected to the line? No, this is not a job for an Arduino, or any low voltage electronics come to that.
thanks for reply. the device in the box like the picture I attached
MarkT:
Connected to the line? No, this is not a job for an Arduino, or any low voltage electronics come to that.
but the arduino always in deep sleep and when any fault appears the OP AMP waking up the arduino. when faults Appears the power line de-enrgised by feeder protector .
JohnLincoln:
You make a commercial product for use in a highly dangerous situation and are asking amateurs for advice?(And I include myself in the amateur category, with over 40 years experience in analogue/digital electronics including RF, microwave and some safety, high voltage and high current applications)
I researching for a university project that my professor told to me
ErfanDL:
thanks for reply. the device in the box like the picture I attached
but the arduino always in deep sleep and when any fault appears the OP AMP waking up the arduino. when faults Appears the power line de-enrgised by feeder protector .
The engineering knowledge gone into making a device like that includes very thorough Faraday shielding to
protect the low voltage parts, protection circuitry all over the place, very careful sealing to prevent moisture
ingress, careful design of the parts to prevent corona discharge being an issue, and lots of testing in a high-voltage
lab, and then safety approval from various industry safety bodies. You try and make your own, bad things are extremely likely to happen.
ErfanDL:
I researching for a university project that my professor told to me
Then I guess I remember the same professor giving the assignment to another student.
Paul
Then I guess I remember the same professor giving the assignment to another student.
We never heard from him again...
Yes, it is installed on the line by the device we make.
You need to back up and start at the beginning:
"Hi , my name is Joe.
I work at [company name].
We make a product [Product name/model number] that does the following....
I would like to ....."
So far nothing is adding up.
For starters, YOU are NOT allowed to place ANY device on ANY power lines , PERIOD ! (EVER !!!)
Only authorized service personal who work for the power company are allowed to do that.
Your story isn't believable or plausable.
If you actually worked for a company that made such a device, you would certainly not be asking us,
and if you were the authorized service person, you wouldn't need us.
Something doesn't add up here and I am not sure yet what it is.
How about providing some proof that anything you have said is true.
For starters, what can you tell us about the device in the photo ?
Who is your professor ?
What country are you in ?
Just for the record, I have worked with equipment exactly like the kind you are asking about. The only
minor difference was our project was 13kV 3-phase and we had a custom transformer made by a company to convert 480 3-phase to 13kV 3-phase. The current transformers (CT) were about 12"x6"
each and there were 3 of them. The enclosure that housed it all was about the size a a VW bug.
The weight of the enclosure was probably more than a VW bug. (we used a fork lift).
We measured the current using equipment to measure the differential voltage output from the CT's
on high end storage oscilloscopes which, if I recall , could calculate di/dt based on the voltage measured
and the time scale using the math function.
Normally the " di/dt " of the 3-phase line on a 13kV line is simply the current sinewave for the line voltage.
I don't remember how we measured the 13kV because I don't recall what probes we had. The current
was no problem because the stepup transformer had the CT's as part of the design requirement.
Why would you want to measure the di/dt ? There are not likely to be current spikes on a 20kV power
line. The power company has to keep the voltage within the required tolerances so it's unlikely you
would see anything other than a normal current sinewave just like we saw.
If you know the power rating for the line you can calculate the di/dt.
Take a 10MW 20kV power line and it's simply:
Prms = Irms*Vrms => Irms = Prms /Vrms
10MW/20kV = 500Arms = 500* sqrt(2) = 500*1.414 = 707.1 Apk.
The voltage from line to Neutral on a 3-phase 20kV line is VLine to Line/sqrt(3)
= 20kV/1.732 = 11,547 Vrms
As far as the di/dt of 3-phase 20kV 60Hz, I couldn't tell you but if you give me the formula
I can put it in Matlab.
AC electronics is not really my area of expertise.
raschemmel:
We never heard from him again...You need to back up and start at the beginning:
"Hi , my name is Joe.
I work at [company name].
We make a product [Product name/model number] that does the following....
I would like to ....."So far nothing is adding up.
For starters, YOU are NOT allowed to place ANY device on ANY power lines , PERIOD ! (EVER !!!)Only authorized service personal who work for the power company are allowed to do that.
Your story isn't believable or plausable.If you actually worked for a company that made such a device, you would certainly not be asking us,
and if you were the authorized service person, you wouldn't need us.Something doesn't add up here and I am not sure yet what it is.
How about providing some proof that anything you have said is true.For starters, what can you tell us about the device in the photo ?
Who is your professor ?
What country are you in ?Just for the record, I have worked with equipment exactly like the kind you are asking about. The only
minor difference was our project was 13kV 3-phase and we had a custom transformer made by a company to convert 480 3-phase to 13kV 3-phase. The current transformers (CT) were about 12"x6"
each and there were 3 of them. The enclosure that housed it all was about the size a a VW bug.The weight of the enclosure was probably more than a VW bug. (we used a fork lift).
We measured the current using equipment to measure the differential voltage output from the CT's
on high end storage oscilloscopes which, if I recall , could calculate di/dt based on the voltage measured
and the time scale using the math function.Normally the " di/dt " of the 3-phase line on a 13kV line is simply the current sinewave for the line voltage.
I don't remember how we measured the 13kV because I don't recall what probes we had. The current
was no problem because the stepup transformer had the CT's as part of the design requirement.Why would you want to measure the di/dt ? There are not likely to be current spikes on a 20kV power
line. The power company has to keep the voltage within the required tolerances so it's unlikely you
would see anything other than a normal current sinewave just like we saw.If you know the power rating for the line you can calculate the di/dt.
Take a 10MW 20kV power line and it's simply:Prms = Irms*Vrms => Irms = Prms /Vrms
10MW/20kV = 500Arms = 500* sqrt(2) = 500*1.414 = 707.1 Apk.
The voltage from line to Neutral on a 3-phase 20kV line is VLine to Line/sqrt(3)
= 20kV/1.732 = 11,547 VrmsAs far as the di/dt of 3-phase 20kV 60Hz, I couldn't tell you but if you give me the formula
I can put it in Matlab.
AC electronics is not really my area of expertise.
Thanks for the long reply!
raschemmel:
For starters, YOU are NOT allowed to place ANY device on ANY power lines , PERIOD ! (EVER !!!)
I will not do this because we have a hotline team !
raschemmel:
Why would you want to measure the di/dt ?
To detect ground fault we need di/dt
Your explanation of the mysterious device on the line was mysteriously missing...
To be frank I cannot believe that I am on the other friggin' side of the world and I have to look up the
information on the 'device' (on the power line) because you are too lazy to do so.
For the love of pete ! If you are going to post on this forum asking for help , AT LEAST DO YOUR HOMEWORK !!!
And just for the record, you have yet to explain what it is you expect us to do about your desire to
build a device to hang on a 20kV power line.
What were you planning on using for communication , RF ? (433 Mhz ?) Or one of these ?
raschemmel:
Your explanation of the mysterious device on the line was mysteriously missing...
To be frank I cannot believe that I am on the other friggin' side of the world and I have to look up the
information on the 'device' (on the power line) because you are too lazy to do so.For the love of pete ! If you are going to post on this forum asking for help , AT LEAST DO YOUR HOMEWORK !!!
And just for the record, you have yet to explain what it is you expect us to do about your desire to
build a device to hang on a 20kV power line.
What were you planning on using for communication , RF ? (433 Mhz ?) Or one of these ?
no I'm using SIM800L for sms and tcp/ip
Ok , so that takes care of the communication
(assuming it will work so close to the piwer lines)
but how do you plan to measure the current and
why are you posting on an arduino forum ?
How do you expect us to help ?
raschemmel:
Ok , so that takes care of the communication
(assuming it will work so close to the piwer lines)
but how do you plan to measure the current and
why are you posting on an arduino forum ?How do you expect us to help ?
raschemmel:
but how do you plan to measure the current
maybe with a ultra low power analog comparator to reading the EMF values and convert it to voltage (need calibration) also need ultra low power MCU.
another way is using the ultra low power OP AMP (AD8541ARZ) to converting the current to voltage ( I asked in first post).
raschemmel:
why are you posting on an arduino forum ?
How do you expect us to help ?
I just posted my question in the general electronic arduino forum that if anyone can helping me to building the di/dt detector with OP AMP.
I've seen this circuit, but I don't know how to calculate the amount of winding coil for 120 amp currents detection. see blow picture
Forgive me for asking but how do you plan to get the 20kV power line INSIDE the donut shaped CT ?
(minor detail I know)
OP AMP (AD8541ARZ) to converting the current to voltage
Please elaborate with a schematic. What current are you referring to in this statement ?
converting the current to voltage
That's the function of a CT (CURRENT TRANSFORMER) , like the ones I mentioned for the 13kV .
Each CT weighed about 20 lbs and was the size of a small dog.
raschemmel:
Forgive me for asking but how do you plan to get the 20kV power line INSIDE the donut shaped CT ?
(minor detail I know)
it's just a schematic the coil is non-contactable like below
video link: https://www.youtube.com/watch?v=kkhye5kHkRs
raschemmel:
How do you plan to get the signal from the fault line indicator shown in the youtube video to the arduino ?You know I have to say, while YOU may have all the details worked out, if you reread this post you will see
that your whole plan comes off as being very 'half-baked' and not thought out because you have deliberately omitted 80% of the details, forcing us to 'interogate' you in game of 20 questions.Is it REALLY so hard to compose an Original Post (that means the VERY FIRST POST) that contains all these details, (including the stuff I HAD TO ADD because YOU NEGLECTED to include it (like the Navigator website link), your latest youtube video, the GSM module link etc. If you are telling us anything because you want
to keep it a secret, then why , may I ask , are you posting on an INTERNATIONAL FORUM to ask about it /Either include everythin in one post , or don't post. It's very simple, because you are wasting out time.
If you had included all these details in your first post I would obviously not sound so annoyed, but every
single new post from you includes a NEW piece of the puzzle that WAS NOT included previously.
What is your problem ?
raschemmel:
How do you plan to get the signal from the fault line indicator shown in the youtube video to the arduino ?
the output of the OP AMP waking up the arduino from sleep and sending the SMS or data and asleep again.
I have no secrets for this project. I think I just asked my questions badly and I apologize for that 
I'm sorry if I took your time.