# Alen Matanovic

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Viewing 15 posts - 1 through 15 (of 18 total)
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• in reply to: volt and current harmonics #12035
Alen Matanovic
Participant

Good thing is first for you to understand the difference between
those two.. Voltage harmonics are caused by Current hamonics which are
generated by nonlinear loads.. Second thing that should be on mind is
that FACTORS THDu and THDi,, of Voltage and Current harmonic distortion
respectively,, are not allways the best solution for expressing the real
situation of distortion in the sistem – More appropriate would be use
of the TDD (Tottal Demand Distortion) factor, especially for Current
harmonic distortion – here's why – if you have “light load condition” in
provide high THD factor,, and it may seem like you have problems with
harmonic distortion which is probably not true (valid only at “light load
condition”) because this Current distortion won't cause anywhat serious
Voltage distortion.. There for, it is better to use TDD istead of THD
for Current harmonic distortion because it shows “real distortion
factor” depending on the available sistem capacity at that moment.. This
is why it's better for use for Current distortion bacause THDi can
varry in a wide range for various types of loads – but it's not
necessairy for Voltage distortion because it does not varries in that
wide range,, so it's still expressed in THDu at many chases (but it doesn't mean that there can not be TDD used)..

Speaking about numbers, here's the table from IEEE 519 std. valid in the US and recommended worldwide:

http://ecmweb.com/images/804ecmIPQfig3.jpg

Voltage distortion is said not to be higher than 8% at the PCC (Point Of Common Coupling – point were the object is connected to the grid, or where other customer could be connected to distribution too)..

Effects of Current harmonics are: heating of the loads, cabels, sistem equipment, transformer windings (the more harmonic current this transformer has to supply, the less
fundamental current it can provide for powering loads. In other words,
because the harmonic current doesn't deliver any power, its presence
simply uses up system capacity and reduces the number of loads that can
be powered),, than nuisance tripping of protective devices,, than least wanted failure or damage of sensitive loads such as computer equipment or PLC loads,, the effect of current distortion on distribution systems can be
serious, primarily because of the increased current flowing in the
system,, and least but not last is Voltage distortion..

Effects of Voltage distortion are: this distortion will have minimal effect on a distribution system, but
unlike current distortion, it isn't path dependent. So harmonic voltages
generated in one part of a facility will appear on common buses within
that facility.. Voltage distortion can cause misoperation of devices that use zero crossing as relevant for taking actions or
measurements (because there might be multiply zero crossing in a single
periode of sinus).. 5th harmonic voltage distortion can cause serious problems for 3-phase motors,, it's a negative sequence harmonic, and when supplied to an induction motor it produces a negative torque..

Feel free to ask for more you want to know ;)..

Cheers,, Alen..

in reply to: design harmonic filter bank for new factory #11922
Alen Matanovic
Participant

rejhan karaman said:

It is very hard to explain it to you briefly.

First of all there is no software that can automatically carry out a calculation of reactive power compensation.

The most important of parameters are:

1) in which the voltage level of compensation is done.

2) what kind of compensation you want. (for your factory is better to dynamic reactive power compensation with thyristors.)

3) which type of electrical consumers is necessary to compensate.

4) single-pole electric scheme of the plant (factory).

So I am at you complete disposal for any additional help and questions.

Regards,

Rejhan.

Hello Rejhan,, are You actually from serbia or? Can I write to you in croatian??

However,, for the benefit of others – let's keep conversation in english :)..

I see you're into subject, so I'd like to ask you few questions :).. First,, what is the simpliest way to calculate reactive power request of the loads? Specially if we have various types of nonlinear loads, such as ASD (or VFD) motors, Computer/Office equipment and Fluorescent lighting – and if their distorted current spectrum is known..

Also, how much do you know about NOTCH (LC) harmonic filters,, and can you suggest some materials/books/papers on their calculation?

I'm doing some harmonic analysis using EasyPower software (don't know if You ever heard of it) and I'm expiriencing some problems regarding calculation of these LC filters.. Since I supposed that this programme don't recognize the differences between load characters (i.e. capacitive, inductive),, I simply added their kVAr powers to gain total reactive power that needs to be compensated.. Once knowing that, it's simple to calculate the inductance for inductor in filter to get resonant frequency of problematic harmonic – using Thompson relation.. And another thing,, all loads are three-phase since this programme has no single-line option.. So as all calculations are for three-phase 400V..

Thank You in advance,, and feel free to contact me also over mail, or facebook if you like ;)..

Regards/Pozdrav,, Alen..

in reply to: Three-phase or single-phase output for UPS? #11899
Alen Matanovic
Participant

Three phase will offer some harmonics cancelation of your nonlinear loads (I assume that there are mostly nonlinear loads, since you need UPS),, but you'll still have problems with “simetry” of your loads.. It actually really depends on type of your loads..

in reply to: tražim posao u inozemstvu #11887
Alen Matanovic
Participant

Prijatelju, moram da te informiram,, na ovoj stranici nećeš vjerovatno
nikada naći posao – iz jednostavnog razloga – nitko ovdje osim mene ne
razumije hrvatski..

Napiši oglas na engleskom ;)..

#11884
Alen Matanovic
Participant

I supose he didn't think about building/making trasformer.. It's just about desinging it using some software, try to google software for designing transformer..  There are probably free / trial / demo versions around..

More interesting to me is, what do you need this transformer for??

K.R.,, Alen..

#11877
Alen Matanovic
Participant

Like others said,, there's few areas where you could get potential savings..

Most significant are:

Heating / Ventilation / Air Conditioning (HVAC system)

Lighting

and Probably Water Consumption (in hotels)

Here's the breakdown from '99. (but it didn't changed significantly):

Since I can not instruct you about your gas or oil consumption, I can only say something about electric savings..

You can possibly achieve savings in Lighting and HVAC system..

About lighting, I hope I don't need to say that there are various solutions, I mean, that there are various diferent types of lightings that can assure You signifficant savings as opposed to Simple old lighting fixtures that have low power factor (PF). Important thing here is to mention that even though New  fixtures can provide good PF, they can still make You, allthough, different type of problem.. Now,, You should not be that affraid,, it's about harmonic distortion that can (and probably will) occur, but solving that issue is still cheaper  comparing to consumption with old lighting systems and possible Utillity penaltys for low PF.. Other important thing on topic is wheter You'r buildings electrical installation is old enough that it was build with reduced neutral that can give You more problems when using new lighting that is electronical nonlinear device wich after all and cause this harmonic distortion..

About HVAC, only significant way of reducing of electrical energy consumption is using of Adjustable Speed Drives  that will run HVAC pumps and fans.. other savings here are not electrical related..

Conclusion here is,, consulting specialists for specific problem,, or providing us with more details on topic (electrical)..

P.S. I apologize for my english, I'm no native speaker ;)..

Regards,, Alen..

in reply to: Harmonic filter for better power quality #11863
Alen Matanovic
Participant

Jim said:

Hi, Alen,

Most of your attachments have been removed from the Blog content. I have not been able to review most of what you sent.

Obviously, this is not the correct media for your investigation.

Regards,

Hi and thanks for your help,, I really appreciate it ;)..

You can find my e-mail above this post by clicking on “little red button – with person logo” named “view user profile”..

But there it is to: alen.matanovic@gmail.com

I've prepared detailed paper with my problem to send you :)..

Regards, Alen..

in reply to: electrical design engineering books/info #11642
Alen Matanovic
Participant

Jennifer said:

Hi,

Thanks again. No, I haven't heard of those sites before today. I tried some of them without success. I was looking for a book entitled 'Transmission and Distribution Electrical Engineering' by Colin Bayliss (3rd edition). The first link you gave me, well, when I went to it, but had a little bit of trouble because after I translated the site to english, not all of it translated. I did try some of the downloads for the book, but they wouldn't work for me. I'm not sure what the problem is. Any ideas or other sources?

In any case, I appreciate your time and help.

Sincerely,

Jennifer

I'm not sure what You have had to translate,, this web site is in english, maybe not completelly, but most is..

Please,, if You need some further help about “downolading” contact me over my email, to stop posting offtopic here ;).. (click litle “person in circle” icon on the left by my name, it's called “view user profile”,, and there You'll find my adress)

Thanks for understanding,, Alen..

in reply to: Harmonic filter for better power quality #11639
Alen Matanovic
Participant

costas said:

Hi. My name is costas. I start my master thesis and i face a problem. i take measurements  in a hybrid renewable energy system (with photovoltaics and a wind turbine) to see the produce power quality of the system (i take measuremets after the inverter). From measurements i notice that i have big harmonig currents. I want to know if anybody have the IEEE standards for power quality (current, voltage) to compare them with the values of the measurements i take and also if there is a way to reduse this harmonics in the real system. Thanks.

Most relevant IEEE standard regarding harmonics is IEEE: 519-1992,, here's link to simple pdf that contain tables with standard limits for THDi and THDu http://www.calvin.edu/~pribeiro/IEEE/ieee_cd/chapters/pdffiles/c9pdf.pdf ..

Hope that helps ;)..

Regards,, Alen..

in reply to: electrical design engineering books/info #11637
Alen Matanovic
Participant

Please try searching for some e-book of interest on ebookee.net and when You click on it look for the “download links” ……. here's the example of direct links for some book I randomly selected: [Link removed by moderator team] trust me, it's simple ;)..

in reply to: Harmonic filter for better power quality #11635
Alen Matanovic
Participant

Could this voltage be something that is mentioned in following Schneider pdf,, page 22.??

http://www.electrical-installation.org/w/images/7/73/EIG_chap_L-2010_haute_def.pdf

(somewhere like in the middle of the page, related to 7-8% increase of fundamental 400V)

Thanks again,, and sorry for multiply posting ;)..

Regards,, Alen..

in reply to: electrical design engineering books/info #11634
Alen Matanovic
Participant

Dear Jennifer,

here's a very usefull web site that can provide You various e-books..

You can simply start searching for “Electrical power systems” or lest say “Electric Power Transformer Engineering ” or even “Control of Induction Motors”……. Anything You may want to know…….

(P.S. if some book You found have no mirror links, You may want to search for another with same title,, because people do “reposting” for those books)

Anyways, the site is : [Link removed by moderator team] so feel free to share Your opinion about how usefull You find it ;) ..

Cheers,, Alen..

in reply to: Harmonic filter for better power quality #11633
Alen Matanovic
Participant

Thank You for brief help..

In meanwhile I've found the way to calculate needed values for capacitor and inductor (needed by programe) and I've got some new “printsreens” to share:

impendance caracteristics @ bus – 3

and reduction of THDi to some 7% at PCC:

Still, I want to ask something more,, what does this voltage presents, and how to determin it's value,, and I mean on the Voltage that is required by Programme as You can see at my first post in fllter data picture? I've set aprox. voltage level of 430V (because main is 400V) just to perform calculation,, and it seemed to work, but I'm looking to find formula for it's precise calculation..

Also, I'm able to change my loads specifications because they are not strictly set,, so if I change from kVA@pf – to – kW and kVAr,, nothing changes, from my perspective of problem,, because if I just “add” those kVArs I'm not sure if I'm geting proper value for my capacitor bank.. Lets say, for example, if my linear load is set as: 100 kW and 20 kVAr, and orher three, ASD 40 kW and 5 kVAr, Fluo. lighting 25 kW and 5 kVAr,, and PC center 30 kW and 5 kVAr,, simple problem is how should I properly add those to gain value for reactive power request by my loads.. I asume that linear load would have “ohmic” character, ASD drive “inductive”,, and Fluo and PCs “capacitive” character,, so simple adding (20+5+5+5=35 kVAr) is definatelly questionable,, more proper way would be “phazor” addition.. but interesting fact is that if I set my filters capacitor bank to 0.035 MVAr it provides better THDi atteunation than it's if I set it to phazor value 20,616 kVAr,, I supose that programe is not able to differ those differences.. Once knowing this “voltage” and “capacitance” it's simple to calculate “inductance” using Thompsons relation..

The only information provided by programmes “manual” and “help” is:

Filter Data:

•  Resistor:  Resistance of resistor of the filter in ohms.

•  Inductor: Real and imaginary impedances (ohmic resistance and inductive reactance) at system frequency in ohms.

•  Capacitor Bank (1 and 2):  The reactive power of capacitors for the system frequency in MVARs at the voltage level specified in kilovolts

… which doesn't helps me very much..

Here are also the links for my calculation of those filters, as well as “reverse” calculation (that's the way I found to calculate my filters) of filters that are provided in example in the users guide of this book (I'm going to apologize again, now for two reasons, first is those materials are not in English, since I'm from adriatic region, but You can see/look only at calculations…. other reason for apologize is “messy” pdfs because my scanner just got broken, so I was using my camera)..

primjer iz knjige” would be “example from the book” and “računanje filtera” would be my filter calculation..

example form the book (please notice that “2.filter” and “3.filter” are notch 5th and 7th filters respectively….. how come is Xc value different for both filters and it's close to 20 MVAr set by the load?……. there You can also see those voltages like 120 kV that are set “in decimal”):

calculation (please look on the page 3. for calculation of my filters,, and on page 2. for reverse calculation of filters from book example):

Kind Regards,, Alen..

in reply to: effect of capacitor #11621
Alen Matanovic
Participant

First of all,, You need to know that capacitor banks are mainly used to improve power factor, and to compensate reactive power request by induction motors..

The effect on installation is little rise in voltage,, and, if there are reactors connected (if problems with harmonic distortion are present), there's also possibility of resonance conditions..

I supose simple “google search” could help if you enter “capacitor effect” and search a little..

There's also a mirror link: [Link removed by moderator team] to very usefull e-book from 2005. (skip to page 13th for a “contents” list, there's almost everything You want to know),, than You may ask further questions about specific problem ;)..

(P.S. I apologize to admin for posting mirror link, hope Usman B. click it first, before You delete it)

Cheers,, Alen..