Hum & three phase powerlines?

[Happy]

G'day all

 

Whilst looking for something, I ran into this comment from an Aussie user at the DIY Audio forum:

 

 

 

In Australia, we have three phase powerlines. Every third house is connected to the same phase to preserve a balanced power drain. You could request your power supply company or utility to change the phase to your house. 

I use electrostatic speakers and valve amps at home. I had similar problems and I suspected DC on the powerlines. The power utility company changed the phase to my house and the hum disppeared.

 

Anyone else has some insight into this?

 

Cheers

D

[sir sanders zingmore]

I don't have insight to add but I'm very interested in hearing the response to this

[Upfront]

Same. Another bump to prompt a response from someone smarter than me

[frankn]

There is a lot of discussion of this on the 'net, Google it.

Whirlpool - http://forums.whirlpool.net.au/archive/2044413

various other places.

If you have a problem I'd be checking/eliminating all possible internal sources of hum before you contact your local utiity.

[Bronal]

Canberra has had three phase for all new developments since the mid-70s.  I imagine other major cities would be the same.

 

Not sure of the proposition being put here - is that three phase can cause hum or can eliminate it?

Edited August 15, 2014 by bronal

[Benje]

If you have single phase supply, you are being connected to one of the three active wires in the street (the 4th wire is a neutral).

So, to balance the loads, houses 1, 4, 7 and 10 in a street will be connected to the same active wire.

Houeses 2, 5, 8 and 10 to the second wire, and houses 3, 6, 9 and 12 to the third wire.

 

Supply from one phase gives you 240 (or 230) volts, as it is root 3 of the 3-phase voltage (used to be 415 volts).  If you have supply from all three phases then you have 415 volts.

 

You will all be fed from a local transformer (they typically supply about 60 houses).  Each wire has a different transformer connection.

 

So, if you have neighbours with power quality issues that are on the same phase, you might have an issue that can be avoided by switching to a different supply wire.

It may be that all of the wires have issues.

 

If you do have a real issue, then you should contact your distributor.  There may be a problem that should be corrected.  The problem could be with the network, or it could be that neighbours are breaching their obligations about the use of the power system.

 

Don't bother asking any more technical questions of me on this matter - my total knowledge of this issue is printed above.  I am not technically gifted knowledge wise, although I do know enough so that I don't muck around with electricity myself, and I would never take a short cut or use home-made/second-grade electrical equipment or wiring or plugs at home. I have had one electrical fire at home 25 years ago involving some DIY wall plugs (not mine) to know not to take such risks.

 

Benje

[Happy]

Wonder how it would work in unit/flat environment and what one has to do to request change of the phase?

[andyr]

I find the original post - or at least this part: The power utility company changed the phase to my house and the hum disppeared. - interesting because I would've thought the last thing a power utility company would want to do is spend time changing an audiophile's phase from #1 to, say, #3 since this:

• takes time to do, and
• upsets their carefully-planned "spreading" of all the houses across the 3 phases, to equalise load.

As I am about to implement 3-phase power into my new house (with one phase dedicated to the hifi), I'd better have a chat to the builder - or more specifically, the builder's electrician - to see whether it is possible to re-assign the phase going to the hifi room, if I subsequently discover a hum problem like the Aussie guy on DIYAudio had.

 

Thanks for posting, David.

 

 

Regards,

 

Andy

[Benje]

Wonder how it would work in unit/flat environment and what one has to do to request change of the phase?

 

Davidro

 

I suspect it depends what wires/phases are available next to where your electricity meter is.

If the meters are all located at a hub next to each of the three phases, it might be possible.

However, the wiring at that point might be the flat's wiring, not the distributor, in which case you would probably have to consult with the flat owner.

 

I think I would want a real, audible problem to consider this.

[mackeb]

I find the original post - or at least this part: The power utility company changed the phase to my house and the hum disppeared. - interesting because I would've thought the last thing a power utility company would want to do is spend time changing an audiophile's phase from #1 to, say, #3 since this:

• takes time to do, and
• upsets their carefully-planned "spreading" of all the houses across the 3 phases, to equalise load.

As I am about to implement 3-phase power into my new house (with one phase dedicated to the hifi), I'd better have a chat to the builder - or more specifically, the builder's electrician - to see whether it is possible to re-assign the phase going to the hifi room, if I subsequently discover a hum problem like the Aussie guy on DIYAudio had.

 

Thanks for posting, David.

 

 

Regards,

 

Andy

 

 

Hello All,

 

As someone who works for an electricity distributor I may be able to shed some light on some of these comments, and as a spark I can maybe help with others.  In the OP that Andyr quotes, the most likely cause and effect was a poor termination causing RF hum which was picked up by some audio gear.  The easiest way to rectify this is easy - re terminate the connection to the house.  Now in and underground area, this is usually done in a 'pillar' (one of those green domes around the place).  In the case it's a matter of moving the cable from one tunnel to another.  It's not always an easy job depending on loading and space in the dome.  If we're talking overhead then moving the service wire from one LV phase to another is accomplished by the use of bucket truck, linesman and all the things that go with it.

 

As for having three phase at your house Andy, the way the switchboard is constructed will dictate exactly how easy or hard it is to change a circuits phasing but it usually is as simple as moving a wire from one place to another.  I've done lots of this sort of thing when having to balance customers loads across the three phases.

 

Apartments and strata units can be a different affair.  Often they use distribution boards with busbars for each phase and breakers mounted accordingly.  Depending on the space in the board and cable length, this may be easy or hard.  How long is a piece of string?

 

Lastly, while all distributors strive for balanced LV phase distribution, it's not always possible.  Changing phases, from a technical electrical point of view will do nothing to improve or worsen your sound, but looking after the connections and terminations from end to end could possibly.  A dirty single phase load in someone else's house may be the culprit, but again it's unlikely.  Another nasty could be a solar inverter on the same phase.

[Happy]

Thanks mack for the comments. So what could an ordinary person do about it? Summon an electrician and show your comments?

Sent from my X10a using Tapatalk 2

[andyr]

Hello All,

 

As someone who works for an electricity distributor I may be able to shed some light on some of these comments, and as a spark I can maybe help with others.  In the OP that Andyr quotes, the most likely cause and effect was a poor termination causing RF hum which was picked up by some audio gear.  The easiest way to rectify this is easy - re terminate the connection to the house.  Now in and underground area, this is usually done in a 'pillar' (one of those green domes around the place).  In the case it's a matter of moving the cable from one tunnel to another.  It's not always an easy job depending on loading and space in the dome.  If we're talking overhead then moving the service wire from one LV phase to another is accomplished by the use of bucket truck, linesman and all the things that go with it.

 

As for having three phase at your house Andy, the way the switchboard is constructed will dictate exactly how easy or hard it is to change a circuits phasing but it usually is as simple as moving a wire from one place to another.  I've done lots of this sort of thing when having to balance customers loads across the three phases.

 

Apartments and strata units can be a different affair.  Often they use distribution boards with busbars for each phase and breakers mounted accordingly.  Depending on the space in the board and cable length, this may be easy or hard.  How long is a piece of string?

 

Lastly, while all distributors strive for balanced LV phase distribution, it's not always possible.  Changing phases, from a technical electrical point of view will do nothing to improve or worsen your sound, but looking after the connections and terminations from end to end could possibly.  A dirty single phase load in someone else's house may be the culprit, but again it's unlikely.  Another nasty could be a solar inverter on the same phase.

 

Thanks, mackeb.

 

In terms of hum on one phase - I was thinking exactly something like a solar inverter in a neighboring house.

 

As an "audiophile sparkie" , I'm interested in your take on one matter to do with the switchboard.  I corresponded with a guy in the UK who was very much into mains effects on sound - he supplied (to Pommies) an additional bus to add to the neutral connections between the MCBs.  It was kind of like an "E" with as many 'bars' as there was MCBs.

 

As I understand it, this gave a much thicker (and lower-resistance) connection for 'neutrals' - which was a good thing to do?

 

 

Regards,

 

Andy

Edited August 15, 2014 by andyr

[Malcolm]

Isolation transformers

[mackeb]

Thanks, mackeb.

 

In terms of hum on one phase - I was thinking exactly something like a solar inverter in a neighboring house.

 

As an "audiophile sparkie" , I'm interested in your take on one matter to do with the switchboard.  I corresponded with a guy in the UK who was very much into mains effects on sound - he supplied (to Pommies) an additional bus to add to the neutral connections between the MCBs.  It was kind of like an "E" with as many 'bars' as there was MCBs.

 

As I understand it, this gave a much thicker (and lower-resistance) connection for 'neutrals' - which was a good thing to do?

 

 

Regards,

 

Andy

 

I think I know what you're referring to, but I can't be 100% positive.  However, the vast majority of switchboards in Australia do not use MCBs that require a neutral at each breaker - rather there is a neutral bar which is a solid brass bar with many screwed tunnels for each circuits neutral.  RCDs that protect a few circuits have their own smaller bars, or if it's only protecting one circuit (RCD/MCB combo) then the tails from the circuit normally are installed directly in the RCD/MCB.  Unfortunately it's really hard to explain without many pictures and being there in person.  Needless to say, the many different types of breaker, boards RCDs etc etc mean there are so many different combos.  Quicklag, MCB, Square D - they're all different!  Old style boards with porcelain semi-rewirable fuses are another thing entirely.

 

Thanks mack for the comments. So what could an ordinary person do about it? Summon an electrician and show your comments?

Sent from my X10a using Tapatalk 2

 

Look, if someone lives in a three phase house already then find a socket on another phase and try that.  If you live in a single phase house and suspect this issue then call a spark and explain the situation, what you've done to come to this conclusion.

 

The trick is you'll have to find a good electrician, someone who is an expert fault finder.  Then once your own house has been eliminated as the source of the problem they can give you a report which you can present to your distributors power quality department and they should investigate it for you.  If there is a problem then they'll fix it.  Here's the clincher too - if your distributor is state owned then you'll get any PQ issues fixed up (it may take  bit of time but it will happen).  If you're on a private network be prepared to fight the case.

[thoglette]

Look, if someone lives in a three phase house already then find a socket on another phase and try that.  If you live in a single phase house and suspect this issue then call a spark and explain the situation, what you've done to come to this conclusion.

 

+1   If you've got all three phases, you can connect your audio gear to the least noisy on.    It ain't the phase, it's the other crappy equipment hung on that phase.  Welders, fridges, inverters, airconditioners etc etc.

 

Swapping phases is easy IF you have space in your main distribution board to move the breakers around.  If you board is full you're out of luck.  And if the neighbours move the fridge you're back to where you started.

 

Better to work on the power supply noise rejection of your "gear".  

[Freedom]

G'day all

 

Whilst looking for something, I ran into this comment from an Aussie user at the DIY Audio forum:

 

 

Anyone else has some insight into this?

 

Cheers

D

 

 

I really can't fathom 'why' this is a topic!

 

A lot of people around here have enough knowledge to know too much BUT too little!

 

You are clutching at straws here!

 

Nuf said!

[Freedom]

As an "audiophile sparkie" , I'm interested in your take on one matter to do with the switchboard.  I corresponded with a guy in the UK who was very much into mains effects on sound - he supplied (to Pommies) an additional bus to add to the neutral connections between the MCBs.  It was kind of like an "E" with as many 'bars' as there was MCBs.

 

As I understand it, this gave a much thicker (and lower-resistance) connection for 'neutrals' - which was a good thing to do?

 

Can you explain more about this?

[andyr]

Better to work on the power supply noise rejection of your "gear".  

 

Or use a 'DC blocker' or an isolation transformer in front of the component! 

 

Andy

[sir sanders zingmore]

Or use a 'DC blocker' or an isolation transformer in front of the component! 

 

Andy

 

what are they ? 

[Malcolm]

what are they ?

There a DC Blocker an a isolation transformer :-)

[andyr]

what are they ? 

 

Hi Trevor,

 

There's thread started by 'guru' under "DIY Audio Projects" which explains it all.

 

That thread inspired me to make up some 'Isotran' units ... which 3 other people have found to improve the sound coming from their system, when placed in front of a source component (CDP, preamp, phono stage).

 

In my case, the improvement came on my TT - djb, Duc, & Steve Tuckett clearly heard the improvement when an Isotran unit was placed in front of the SMPS which was powering Steve's speed controller which drives my 'SkeletaL'.

 

The only problem with these Isotran units is they are only rated to pass 250ma of mains current - so can't be used with a power amp (except by those who use 5w SETs!  ).

 

For these, we need the DC blocker - which was what 'guru' was posting about.  Whereas the isolating transformer is simply a 1:1 mains transformer (which, by virtue of the magnetics that enable it to work, stops any DC which might be present on the primary winding from passing through to the secondary winding).  A DC blocker is a combination of caps and diodes, which also doesn't let DC pass.  The advantage here is that (with sufficiently rated diodes and caps) it can cope with 6 or 7 amps of mains current - which means it can be used with just about any power amp.  In fact, guru reported that he used it in front of his plasma TV and noticed a significant increase in picture quality.

 

 

Regards,

 

Andy

Edited August 17, 2014 by andyr

[Guest guru]

Using it on the plasma was only for people who don't trust their ears. Those that do can hear quite easily what it does for audio systems.

[awty]

A cheap $8 240v AC EMI filter installed on my TT seem to make the motor more quiet and run more smoothly, but I dont have djb, Duc, & Steve to verify.....do they do house calls?

[Malcolm]

 

The only problem with these Isotran units is they are only rated to pass 250ma of mains current - so can't be used with a power amp (except by those who use 5w SETs!  ).

 

Lucky mines rated at a 30 amp continuous draw :-)

[Guest guru]

So you're running the oven off it, bet the souffle's rise perfectly.