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Topic Title: Line current harmonics for Y to Y systems.
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Created On: 17 September 2009 05:44 AM
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17 September 2009 05:44 AM
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makeitwork

Posts: 23
Joined: 10 June 2009

Hi all
i need some confirmation regarding harmonics on a Y to Y 3 phase system. Assuming a 3 phase supply supplying a 3 phase non-linear load.The neutral points are connected to ground. Will the line current contain triplen harmonics? In the case where there is a neutral wire,will the line current contain triplen harmonics?Thanks.

Regards,
alvin
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22 September 2009 08:40 AM
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jafarpour

Posts: 198
Joined: 14 August 2005

In Y connection system, the line current is same phase current, therefore when there is a suitable path for third harmonic current (neutral point) we face to it in line current. In delta connection we have third harmonic current just in phase current which formed delta connection and it is absent in line current. Of course there is an exception for that mentioned fact. For more information you can refer to General electrical riddle No.13 from http://electrical-riddles.com
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24 September 2009 05:59 PM
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Backintime

Posts: 282
Joined: 11 April 2007

The two links below may be able to help:

http://www.allaboutcircuits.com/vol_2/chpt_10/7.htmlhttp://www.allaboutcircuits.com/vol_2/chpt_10/7.html

http://www.theiet.org/forums/f...id=23598&enterthread=y
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09 October 2009 05:04 AM
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makeitwork

Posts: 23
Joined: 10 June 2009

Thanks guys.
However,i'm still confused. After reading this
http://www.allaboutcircuits.com/vol_2/chpt_10/7.html. It seems to say that for a case where a three-phase balanced supply is connected to a wye connected non-linear load and both neutral points are grounded,the line or phase current will be free from triplen harmonics but in the case where a fourth wire is connected between the neutral points, the line current has triplen harmonics. Is this statement true? I've tried generating this phenomenon in SIMULINK, it seems that the line current do have triplen harmonics regardsless of weather neutral points are grounded or connected with a neutral wire.
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21 October 2009 12:31 PM
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makeitwork

Posts: 23
Joined: 10 June 2009

Originally posted by: jafarpour

In Y connection system, the line current is same phase current, therefore when there is a suitable path for third harmonic current (neutral point) we face to it in line current. [\q]

Hi jafarpour,
you are saying that in Y systems when there is a neutral wire connecting the neutral points of the source and load,there will be triplen harmonics on the line current? but when both neutral points are grounded,there won't be triplens harmonics on the line current?
I actually try simulating this scenario,unless i am doing something wrong, there are triplen harmonics in both cases.

Regards.
alvin
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22 October 2009 02:36 AM
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tonysung

Posts: 630
Joined: 14 September 2001

Originally posted by: makeitwork

Thanks guys.

However,i'm still confused. After reading this

http://www.allaboutcircuits.com/vol_2/chpt_10/7.html. It seems to say that for a case where a three-phase balanced supply is connected to a wye connected non-linear load and both neutral points are grounded,the line or phase current will be free from triplen harmonics but in the case where a fourth wire is connected between the neutral points, the line current has triplen harmonics. Is this statement true? I've tried generating this phenomenon in SIMULINK, it seems that the line current do have triplen harmonics regardsless of weather neutral points are grounded or connected with a neutral wire.


Hi, Alvin

In star-star connection, the triplen and other higher order harmonics will be present in the line (and phase) conductors no matter a neutral conductor is there or not. If a neutral wire is present, the triplen harmonics will sum together in the neutral while all other harmonics and the fundamental 50Hz components will sum to zero.

Only in a delta-delta connection, the triplen harmonics will only be found in the delta phase windings but not in the line conductors.

Your Simulink model should give you the above mentioned results.

Kind regards

-------------------------
 Tony Sung
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25 October 2009 01:08 AM
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makeitwork

Posts: 23
Joined: 10 June 2009

Hi Tony,
thanks for your confirmation reply.However,i still have some questions. We know that the triplen harmonics are canceled in line to line voltages for a Y system.Somehow some articles portray it as some sort of benefit. May i know what is the benefit of this towards three phase systems? Does three phase loads look at the supply as line to line voltages rather than phase voltages?
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