How stable should consumer electricity supply voltage really be?

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casewindow

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Topic # 123228 29-Jun-2013 14:25

I have read on this page that NZ consumer voltage is 230v +/- 6% which means a low of 216.2v and a high of 243.8v
http://www.trustpower.co.nz/index.php?section=79

I have a UPS that is showing fluctuations in the last 6 hours within this range (222v to 238v), though the fluctuation is fairly regular (it changes 15-20 times an hour significantly and upto 40 times an hour in smaller increments).

But what should be realistically expected - should the voltage ideally be very stable or is it expected that 15 to 20 times an hour it will move 'significantly' within the expected range?

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Reply # 847150 29-Jun-2013 15:39

Lines and transformers have resistance and as the load changes the voltage changes.
Is the variation causing some specific problems for you?

They appear to be within the published specification. Perhaps they could improve the voltage stability by a number of means, such as doubling the size of the conductors in their distribution network. But what is the benefit and who's going to pay for that?

#include <standard.disclaimer>

Kraven

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Reply # 847151 29-Jun-2013 15:41

It's not a <$200 Dynamix UPS is it?

SATTV

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Reply # 847154 29-Jun-2013 15:50

The only thing that is guaranteed is the frequency. 50Hz +-0.2% if I recall, the voltage is a best effort and is dependent on load and switching. If they have to shunt power from one area to another it might cause a drop in power, when they stop the shunt it might cause a rise in voltage.

I know enough to be dangerous

richms

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Reply # 847159 29-Jun-2013 16:12

The standard is pretty meaningless as it doesnt cover what time it is averaged over, seems odd that its only 6% tollerance, I was under the impression it was 6% under or 12% over or something like that.

In anycase, the only things that care are resistive heaters and to a lesser degree motors.

Richard rich.ms

casewindow

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Reply # 847161 29-Jun-2013 16:13

Kraven: It's not a <$200 Dynamix UPS is it?

No, it is an APC SmartUPS - fairly good one and I purchased it brand new a few years back.

I am interested in those Dynamix UPS from the likes of DSE though. Are they any good? I assumed they were a good price as they're NZ made - though that may be a bad assumption.

alexx

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Reply # 847162 29-Jun-2013 16:14

The electrical regulations define the allowable variation.
http://www.legislation.govt.nz/regulation/public/2010/0036/latest/DLM2763653.html

Electricity (Safety) Regulations 2010

Section 28: Voltage supply to installations
   •   (1) The supply of electricity to installations operating at a voltage of 200 volts AC or more but not exceeding 250 volts AC (calculated or measured at the point of supply)—
    *    (a) must be at standard low voltage; and
    *    (b) except for momentary fluctuations, must be kept within 6% of that voltage.
   •    (2) The supply of electricity to installations operating at other than standard low voltage (calculated or measured at the point of supply)—
    *    (a) must be at a voltage agreed between the electricity retailer and the customer; and
    *    (b) unless otherwise agreed between the electricity retailer and the customer, and except for momentary fluctuations, must be maintained within 6% of the agreed supply voltage.
   •    (3) A person who supplies electricity commits a grade A offence if he or she supplies electricity to an installation in breach of this regulation.

===

Elsewhere in the regulations it defines standard low voltage as 230 volts AC.
http://www.legislation.govt.nz/regulation/public/2010/0036/latest/DLM2763510.html

Note there can also be momentary fluctuations outside this range.

If your equipment is unable to operate correctly when there is a variation of up to 6%, then you should return it as not fit for purpose (assuming you are as consumer under the consumers guarantees act).

#include <standard.disclaimer>

casewindow

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Reply # 847163 29-Jun-2013 16:15

alexx: Lines and transformers have resistance and as the load changes the voltage changes.
Is the variation causing some specific problems for you?

A few times a day - usually 11am, 1pm, 3pm or 11pm (though not all of these) the UPS switches to battery power. It seems that the UPS does this at least once a day - and I am concerned about the life of the UPS / the effect on other equipment around the house that just have surge protectors.

I decided to really start analysing the voltage by installing powerchute and I was surprised after 1/3 of a day to see just how much the voltage varies.

richms

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Reply # 847164 29-Jun-2013 16:19

Does it define momentary fluctuations?

And a short switch to battery but no beeping is normal on UPS's, its just testing the batteries under load. If they fail it will switch back and if set up email you an alert that the batteries are stuffed.

Richard rich.ms

casewindow

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Reply # 847167 29-Jun-2013 16:26

richms: Does it define momentary fluctuations?

And a short switch to battery but no beeping is normal on UPS's, its just testing the batteries under load. If they fail it will switch back and if set up email you an alert that the batteries are stuffed.

It is not a short switch - it switches between battery power and AC over a 30-60 second period at the times I listed (though not all of these - usually at least one though). It beeps during this time and the 'on battery' indicator light is lit at the front.

Afterwards the battery starts charging, so it is seen by the UPS as a loss-of-power event.

alexx

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Reply # 847171 29-Jun-2013 16:29

Does it tell you how low the voltage reached, e.g. like this...
http://forums.apc.com/message/24224

#include <standard.disclaimer>

richms

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Reply # 847172 29-Jun-2013 16:29

It might be freaking out at the high frequancy ripple control noise on the powerline. I know that it totally skitzo's some light dimmers. Luckilly on the shore we dont have that on the lines.

Richard rich.ms

casewindow

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Reply # 847207 29-Jun-2013 18:34

alexx: Does it tell you how low the voltage reached, e.g. like this...
http://forums.apc.com/message/24224

Powerchute allows exporting the data.

The lowest so far today is 211.6v (4.6v less than the allowed minimum threshold of 216.2v)
The highest so far today is 240.4 (3.4v less than the allowed maximum threshold of 243.8v)

sbiddle

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Reply # 847225 29-Jun-2013 19:41

casewindow:
richms: Does it define momentary fluctuations?

And a short switch to battery but no beeping is normal on UPS's, its just testing the batteries under load. If they fail it will switch back and if set up email you an alert that the batteries are stuffed.

It is not a short switch - it switches between battery power and AC over a 30-60 second period at the times I listed (though not all of these - usually at least one though). It beeps during this time and the 'on battery' indicator light is lit at the front.

Afterwards the battery starts charging, so it is seen by the UPS as a loss-of-power event.

My pick would be your UPS is probably tripping on the ripple signals. Not all UPS's will trip on these, but it can get annoying if you've got one that does.

Ripple signals were historically just used for ripple switches at night, but are increasily being used for network load management as they're an exceptionally powerful way of controlling network load.

casewindow

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Reply # 847232 29-Jun-2013 20:26

sbiddle:
casewindow:
richms: Does it define momentary fluctuations?

And a short switch to battery but no beeping is normal on UPS's, its just testing the batteries under load. If they fail it will switch back and if set up email you an alert that the batteries are stuffed.

It is not a short switch - it switches between battery power and AC over a 30-60 second period at the times I listed (though not all of these - usually at least one though). It beeps during this time and the 'on battery' indicator light is lit at the front.

Afterwards the battery starts charging, so it is seen by the UPS as a loss-of-power event.

My pick would be your UPS is probably tripping on the ripple signals. Not all UPS's will trip on these, but it can get annoying if you've got one that does.

Ripple signals were historically just used for ripple switches at night, but are increasily being used for network load management as they're an exceptionally powerful way of controlling network load.

Could be the case. I set it from high sensitivity to low sensitivity for a while and I am pretty sure I saw less occurrences. At that time the battery was near end of life and the short outages would cause it to almost lose all power (then the 'replace battery' light came on).

I have since replaced the battery and decided to put it back to high sensitivity as during the time it was on low sensitivity, a piece of equipment had a power supply die on it (though the PSU for this equipment was low spec so it could have just been coincidence)

gumboot19

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Reply # 847236 29-Jun-2013 21:04

First, (In my simple opinion) there may be a loose connection in your incoming power cabling, Copper cables tend to work loose (lose tension in connectors) over time. This will not help issues.
As an aside most lamp bulbs are rated at 230volts. We have found that the European sourced? bulbs rated at 250volts appear to last longer, maybe due to the advertised? additional voltage capability of the bulbs. Would be happy to be proved wrong here. Possibly other electric equipment ma have the same potential issues?

Regards
Darren

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