help on thesis

[n30nl16ht]

MABUHAY sa lahat ng mga EE! ahehe

hello guys this is my first time to post here, anyway i need some help on our thesis

its entitle DEVELOPMENT OF A BUILDING POWER QUALITY MONITORING UNIT w/ wireless application, basically what were trying to achieve is to fabricate a monitoring unit that will be attached to the service entrance drawing data from a CT and rogowski coils. We are planning to record real time voltage quality and harmonics as is required by the IEEE. So far, we have got our initial layout of the circuitry and the components involved. We will be using two atmega32s two process the data one for the harmonics and the other for the voltage quality then will combine both info in one atmega128 chip and send it to sd module for storage purposes. right now were having problems sa circuit. Do u guys think its costly? what would be a better way to do this? THANKS sa repz

[zer0w1ng]

3 MCUs! It will be an overkill and more complicated.
A single MCU is more cost effective.

A few questions:
-How fast do you log the voltages? harmonics?
-What will be the data format on the SD card? readable by any PC?
-Why are you using a CT when you are only measuring the voltage and not the current?

I am not an EE and I'm curious on how is the harmonics measured and sensors used.
How is this done?

[Dandy]

Hi Sir,

Mas maganda siguro kung i-detail kaunti ang Technical Requirements, as in 1..2..3...4.   Kung puwede, paki-sama na din po ang "Features", pati na ang "Functional Description + Block diagram".  Ito po ang mga importanteng element para maka-decide  kung anong solution ang gagamitin.

I have seen ready made solution - from low and very high tech one from the show in HK and Canton fair show,  solution are there, it's just a matter to know more about the "requirements".

I am concern about "Safety"...

[marcelino]

3 MCUs!!!! overkill nga... i have seen a single avr32 works. i think, isa nga lang ok na.
Perhaps, you wanted to have a simultaneous sensing and calculation. if this part is so critical that you wanted it to be derived so fast, i suggest you can use FPGA. however, interfacing some peripherals to FPGA is much more tedious than that of an MCU.

More details will be helpful...

[zer0w1ng]

I am not an EE and I'm curious on how is the harmonics measured and sensors used.
How is this done?

I googled and found out that AC line harmonics is measured using low freq spectrum analyzer.
http://www.allaboutcircuits.com/vol_2/chpt_12/4.html

It can also be done using Fourier Transform.

This can be solved using software in DSP.
I am not very sure if AVR has enough MIPS for this application.

If we want to measure up to the 5th harmonics, that will be at 300Hz thus the sampling freq should be 600Hz min.
To be more accurate a 1KHz sampling is recommended.
But depending on how often its logged, the AVR might be able to do the job.

[rdpzycho]

http://elm-chan.org/works/akilcd/report_e.html

applied to audio.

[motion55]

@TS

What is your background? And what do you hope learn by producing this project?

The reason I am asking is because you don't have to start everything from scratch. If your thesis is mainly on "making a building monitoring unit" and not about the messy stuff of fabricating circuit boards, then it is better to use pre-existing boards like the Atmel evaluation kits. With an evaluation kit then your time will be well spent in doing the actual thesis itself and not on trying to procure parts, fabricating the board, etc.

If this way is acceptable to your thesis adviser (you may have to do a little convincing), then check out the Atmel site and pick a kit that can be best modified for your project. Even if you haven't gotten one yet, try to see if you can write software from the freely downloadable tools for your thesis. This is to make sure the strategy is viable.

Should your professor insist on making a final model without the benefit of the starter/evaluation kit, you can always finalize by transferring the design to your own fabricated board, removing the unused parts of the evaluation kit from the final design.

[anthonydp]

@n30nl16ht

I would recommend that you read this informative equipment manual .  This is a commercial power analyzer product but you can get ideas presented on its manual on how to implement your project.  After you completed your project, we hope you can share pictures and experiences here.

[n30nl16ht]

Here's a more detailed info list in our project...

We are trying to fabricate a building power quality monitoring device that will be setup as an extra device in the service entrance pole outside of the building. So the device is expected to withstand environmental conditions.

This is our conceptual framework:

<a href="http://s150.photobucket.com/albums/s99/n30nL16ht/SWEARERS/?action=view&current=ConceptualFramework.jpg" target="_blank"><img src="http://i150.photobucket.com/albums/s99/n30nL16ht/SWEARERS/ConceptualFramework.jpg" border="0" alt="Conceptual Framework"></a>

Objectives of the Study:
1. To create a power quality monitoring device using ADE7758, an energy metering chip, that could sample the voltage behaviour from a load power source, primarily from a CT source.
2. To evaluate the harmonics of the load power source by attaching rogowski coils with RC integrators on the three secondary line of the transformer banking.
3. To implement and apply two ATMEGA32 microcontrollers that will independently gather data from the energy metering chip and rogowski coils.
4. To implement a mother MCU, namely the ATMEGA128 to interpret the data gathered from both sub MCUs. Voltage deviations and current harmonics will then be compared to the standard values provided by IEEE using a comparator circuit for which the values are stored in the microcontroller.
5. To implement an Analog-to-Digital Converter within the microcontroller that will process the waveform data from the energy metering chip and store it together with the other data needed into a separate storage device(i.e. SD card, EEPROM).
6. To implement a wireless network using ZIGBEE or BLUETOOTH as an intermediate to constantly transmit data from the device unto any compatible recieving platfrom such as a PC or laptop for easy and handy access of data.
7. To construct a dedicated software that can retrieve these data and reconstruct the actual data in phasor form or waveform.

Scope and Limitations:
• The voltage levels that will be applied to the device will not be greater than 250 V.
• The device will only be applied and implemented at the service entrance of a building.
• The rated maximum input current should be 5 Amperes.
• Wireless transfer is only limited to the capabilities of the ZIGBEE/BLUETOOTH transmitter.
• The SD card used will only be limited to a storage not greater the 2Gb and therfore if full, the device will automatically dump the last encoded entry in the storage.

[n30nl16ht]

oops sorry bout the code thought the posting supports it...

anyway @ zerowing: we are using CTs since ADE7758 utilizes both voltage and current as inputs

Salamat nga pala sa lahat ng nagpost, greatly appreciated po, is it really overkill pg tatlo ang MCU kac we thought one ATMEGA32 couldn't handle all the monitoring kac 32mb lng ung mem cap nya so eto nlng ang npagisipan namin. Is there a better way mga sir?

Were from iligan city, lanao del norte, mindanao nga pla so its very hard to procure the components here... any suggestions?

[zer0w1ng]

anyway @ zerowing: we are using CTs since ADE7758 utilizes both voltage and current as inputs

Are you sure that the voltage is read via a current-transformer?
Where in the datasheet is this stated?

I am curious with this...I'll d/l and read the datasheet to be sure.

Hmm...
Here http://www.analog.com/static/imported-files/data_sheets/ADE7758.pdf
Page 17, on test circuits, the voltage is read via a voltage divider 1Mohm and 1Kohm and with a 33nF cap in parallel.
It does NOT go via the CTs.

--

Take note that ADE7758 IC is not for power quality monitoring but for POWER CONSUMPTION and POWER FACTOR calculation only.

Also your objectives is too broad and conflicting and you may not be able to implement them all.
For example, with the ADE7758 chip, the ADC is internal.
You can't read harmonics with ADE7758 as well.

PS: Rogowski coil is a type of Current Transformer, again this cannot measure voltage quality.

[n30nl16ht]

aw sorri for the confusion, current is drawn from the ct and the voltage is from the voltage divider, ahehe, u can see it in our conceptual framework from the link i provided (suppose to be the image).

heres the link again.
http://s150.photobucket.com/albums/s99/n30nL16ht/SWEARERS/?action=view&current=ConceptualFramework.jpg

[n30nl16ht]

up, pa help nman guys, cge na...

[iyo karpo]

There are many references available from manufacturers:

http://www.eaton.com/EatonCom/Markets/Electrical/BusinessPartners/ConsultantsEngineers/TechnicalPapers/index.htm

http://www.geindustrial.com/solutions/engineers/specifiers_table.html