WA power supply

[jakestar]

Hi fellow SNA'er s

I thought I'd share my recent experiences with power supply fluctuations. I realise this topic has been discussed previously but it seems WA power supply is still lacking. What's it like in remainder of Australian states and cities?

 

Last year about this time of year I experienced readings up to 254V incoming to my home. (A friend living 15 minutes away was experiencing voltages in excess of 260V).

 

Over the past couple of months I've noticed incoming voltages on my Thor power station have been reduced to around 230V. Happy days for stereo gear and in particular valve pre and power amps, well recognised to not react well to voltage fluctuations.

 

However a few days ago I was reading incoming voltage at just over 212V. I thought it's worth an email to Western Power, the only power supplier to Perth, and WA.

I was contacted by a representative the following day to discuss the issue when he arranged for a tech to come to site the following day. Great service I thought.

 

When a tech arrived the following day during early afternoon he determined incoming voltage at 228V which coincided with my readings. I have incoming voltage on my Thor power station and $20 voltage meter from Jaycar when I suspect weird voltage.

He was surprised when I showed him photo taken of the voltage readings and said that was too low and he would investigate substation distribution and possibly arrange for sharing/equalising the power loads.

 

Happy days I thought when subsequent reading yesterday and earlier today showed incoming voltage around 230V. Note the voltage is never stable as always fluctuates a few Volts but looking forward towards less variations.

I was very surprised my earlier hopes were voided when I read incoming voltage on my trusty Jaycar meter this evening at 211.8V.  Scary stuff.

Fortunately I turn off my stereo around 4.00pm each day and avoid these big power swings which I attribute to folks arriving home from work and powering up appliances such as AC, TV, cooking and washing machines.

My point is most folks have no idea what the incoming voltage is to their homes and can be forced to pay for repairs or replacement for appliances and in our case, stereo equipment which fails.

 

Any thoughts or suggestions for having our power suppliers provide a voltage which is far more stable. I acknowledge there is an allowance of +or - but the supply seems too far off the mark.

I am somewhat comforted when I read outgoing voltage for my stereo from the Thor power station set at 240V but there are limits. Fingers crossed all the other household appliances survive.

[HypnoToad]

You would think it would be more closely regulated, how that being said most audio devices would have a high tolerance to voltage fluctuations, not talking about actual power surges but the fluctuations you are referring too. Take an amplifier with a linear power supply, if the voltage increases by 10%, the voltage regulators will take care of this easily. For example a stock 7812 regulator for example which has an output voltage of 12vdc has a maximum input voltage of around 35vdc. With those that have a SMPS this is also of little consequence.

 

IMO it would only be wild voltage swings or actual surges that could affect of damage your equipment. That's not to say that the power companies shouldn't be trying to put out as close to 240vac as possible.

[mbz]

Vaguely recall that the mains should be 240Vac +/-6% meaning
226-254Vac is not unexpected. Readings of 211V and 260V are
disturbing since it may cause damage to electrical appliances
over time (currently working on an amp that was set to 220Vac
and ran long term on 240Vac)

 

I understand that matching the power generation to the load
can be a little tricky however the load over each day type
(mon,tue,,,fri,holiday,,) is well known so such swings are
of concern. Maybe there is a new factory in the area that's
coming on line???

 

Suggest monitor the voltages to try and identify a pattern
or if it's "random". If the massive swings continue then I'd
take it to the ombudsman...

[jakestar]

Yes. The big voltage swings are the concern.

 

Interestingly, the WP tech who attended indicated high voltage lines have automatic voltage regulation but normal residential power supply lines are not.

Makes one wonder how difficult it would be to install some automatic voltage regulation controller to the grid. I keep imagining there is a guy turning a knob to adjust output if the value moves outside limits. Surely that's somehow automated these days.

 

Personal solar panel uptake surely plays a part in problems regulating voltage but one would hope the power authority is more proactive in adjusting to society power choices.

I can't wait for the day when self powering and collecting/saving electricity becomes affordable to all allowing us to disconnect from the unstable and unreliable grid and rely on clean and regular power. 

[cyclingsteve]

Yep I can confirm the voltage swings are crappy as the power rose a bit to high oneday and fried components on my vintage Linn Sondek!!! Was subsequently told by by the dealer that with the older sondeks you need to always turn the power switch off at the mains when not in use .

[Guest Muon N']

Used to be a constant 250vac at the wall in my Brisbane suburb, but sometime in the last several months they changed something and now it hangs close around 239vac.

 

Seems to be widely variable in how much and how variable it is depending on where you are in this country, right down to the local substation.

[mbz]

Worth keeping in mind that power is generated as 3 phase and a key target is to balance the load on each phase, so expect people connected to the other 2 phases to see the same voltage swings as you. If you are in a purely residential area then hard to work out why, if you have some large industry then that may explain...

[HypnoToad]

22 hours ago, jakestar said:

I can't wait for the day when self powering and collecting/saving electricity becomes affordable to all allowing us to disconnect from the unstable and unreliable grid and rely on clean and regular power. 

You and everybody else.

[jakestar]

 

4 hours ago, mbz said:

Worth keeping in mind that power is generated as 3 phase and a key target is to balance the load on each phase, so expect people connected to the other 2 phases to see the same voltage swings as you. If you are in a purely residential area then hard to work out why, if you have some large industry then that may explain...

Nearest light industrial area about 5km away. The big swing even had the tech surprised.

I'm sure they're working at it but yesterday evening still in high teens.

A friend suggested with tongue firmly in cheek that the power slowed down going up the hill.

Must say though that I'm happier to see voltage lower than previous 250+V levels but in an ideal world the supply is  stable regardless of loads. 

 

I've been wondering after reading issues claiming for stereo gear as well as other appliances by a SNA'er who was recently burgled, if similar claims for failed equipment due to power voltage swings, would fare with insurances companies. 

[Monkeyboi]

Apologies in advance for the lengthy reply.

 

Most insurance companies will pay out under the "fusion" conditions in the policy, however what actually defines "fusion" must be carefully interpreted as many policies are either vague or ambiguous with this term.  Remember insurance is a game or gamble between the insured and the insurer.  Their game is to get your premium and hopefully never have to pay out on it.

 

Back to the WA power grid. The nominal grid voltage is supposed to be 240v per phase wrt neutral. Most WA domestic premises are fed with a single phase 70A supply.  Some premises may have 3 phase as is my Perth home. My rural property is single phase but 100A supply from its own 25kVA pole mounted transformer that isn't shared with any other property as the original owners had an electric kiln for firing pottery and glass blowing therefore because of their increased supply requirements they purchased the transformer that feeds my property exclusively.   

 

Voltage throughout the day and night varies considerably.  Western Power say this is normal for single phase rural supplies as the street distribution is done as HV over considerable distances and properties are fed via a stepdown pole mounted transformer the 240v supply will vary with load, which is to be expected.  Also grid connected solar / wind inverters will also have an influence on the mains supply voltage inside the premises network whilst feeding back into the grid.

 

Whilst a slightly lower supply voltage may cause problems with some domestic appliances (older non-inverter compressors, pump motors etc.) the effect isn't significant or detrimental to resistive loads such as kettles, electric stoves, heaters and many devices using a switch mode power supply (SMPS).  Also most hi-fi equipment won't be damaged or significantly effected if the mains voltage drops a bit.  Non-synchronous a.c. induction turntable motors will run a bit slower (but these types are few and far between anyway).

 

Where the danger is in when the mains voltage is too high.  Some SMPS will tolerate a higher than nominal input voltage as good SMPS units can handle a wide range of input voltage (within limits of course), but a linear transformer power supply is completely different story.

 

Occasionally I see an amplifier delivered to my workshop for repair.  The common comments the customer makes are on the lines of "I could smell this burning type odour, then the device stopped working."  On opening up the device one often finds on some units that something has failed in the power supply.  A common problem with gear brought over from the EU or parts of SE Asia is the transformer and or some other component in the power supply have failed. In many cases of transformer supplies designed for 220v operation the primary winding has gone open circuit as a common design of EI transformers is to have a thermal fuse imbedded in the primary winding close to the core.  This thermal fuse is designed to become open circuit when the internal temperature of the transformer exceeds about 120 deg. C.  Unfortunately even if the device hasn't been abused or even if no other component in the device has failed, the transformer can easily overheat due to excessive core saturation.  That's why I advise people not to buy transformers with 220v primaries for use on the Australian electricity supply for their DIY projects.

 

So what's wrong with a 220v transformer on a 240v supply?  Well if you do the calculation, the 240v is ~ 9% over the nominal 220v  voltage rating of the transformer.  No big deal as some may say. But what happens when it drifts up to 260v as @jakestar commented?  Redoing the calculation this increases the error to ~ 18% too high on a 220v transformer.  This in turn translates by the same error to the secondary winding(s), which may stress the other components down the chain.

 

Over voltage is a cause for concern for linear power supplies that use a mains transformers because the increased primary voltage can saturate the core which causes a steep rise in operating temperature even without a load connected. Transformer design is a complicated science and many manufacturers try to do three things -

•  optimise the efficiency of the transformer.  This is often done by operating the transformer just below the point of the core saturation, but this makes the transformer less tolerant of overvoltage operation (not talking transient voltage spikes here).
•  keeping the size and weight to a minimum for the VA rating of the transformer.
•  reducing manufacturing costs.

So on your next equipment purchase or DIY project don't buy a bit of kit or transformer that has a 220v rating and run it directly from a 240v supply.  You're just asking for premature failure of the transformer or other electronic components within the device.  Just think about the consequences of a 220v tube amplifier connected to a supply that may drift up to 260v.  Elevated HT supply, filaments operating at 18% over their nominal voltage (unless downstream regulated) will contribute to shorter tube lifespan, stress on the other components and increased operating temperatures all working towards reducing the operating life of the equipment.   

 

Once again, apologies for the lengthy post but I'm attempting to explain the problems in not so technical terms that hopefully most readers can comprehend.

 

Cheers,

Alan R.

[jakestar]

Thanks  @Monkeyboi - very informative and clear input. Certainly enough information for a non tech savvy person to get my head around

 

As an update since WP techs attended my power supply concerns they installed a monitor to my meter box for 3 days to identify fluctuations on a continual basis. 

The tech rang the following day to confirm they had shifted my supply voltage slightly and to advise if still too high or low.

I can happily report that so far my power supply variation has been far more even ranging from mid 240V to low 230v, a very good outcome compared to previous variations.

 

When I read the potential damage when using 220V gear I'm glad my valve amp is Aussie designed and built for 240V. Much of my other gear is also 240V and 230V. I guess if ordering from O/S to ensure one chooses the best voltage for local supply matching or ensure a step down transformer is in the line.

I'm sure nobody needs or wants disputes with insurance companies should claims arise.

Cheers

Peter

[Guest deanB]

Alan @Monkeyboi I monitor my house voltage at the wall socket with a Jaycar type device. What is the minimum and maximum voltages a 240v power amp (valve in my case) should be used at, +/- 5% or...?

I've been erring on the side of caution at +/- 5%. (228v - 252v)

Edited February 4, 2020 by deanB