Line transients...

[Don Y]

From time to time, we seem to experience a power \"glitch\", once a
day, at roughly the same time -- usually ~3AM. (but, not every day...
just \"periods\" when it manifests followed by periods where it is
completely absent).

It\'s not a problem, for the most part, as everything is on UPSs, here
(the microwave oven seems to complain the most as it isn\'t on a UPS
and its damn clock often resets -- I long for the day when appliances
have synchronized clocks or NO clocks!!!)

I assume this is some sort of switching transient that affects the
entire city (?) -- or, at least large portions of it.

(our services are below grade so not likely caused by something
physically interfering with the transmission lines)

I\'m turning my attention to the design of the power systems for
my current project and figure it would be prudent to put some
line-monitoring capabilities into it (if only to let it anticipate
such problems and plan ahead).

So, the questions are:
- how often to sample (to be able to catch transient events)
- maximum peak likely to be encountered

[Of course, I have to anticipate what the power conditions are
likely to be in other parts of the market (US consumer and,
separately, commercial/industrial) and not just rely on my own
observations.]

I\'m tempted to buy a line monitor just to see what they\'ve done
(in terms of hardware interface; the signal processing software
won\'t be a problem). Recommendations? (again, two/three different
markets, as above)

 

[Anthony William Sloman]

On Wednesday, March 30, 2022 at 1:25:36 PM UTC+11, Don Y wrote:

From time to time, we seem to experience a power \"glitch\", once a
day, at roughly the same time -- usually ~3AM. (but, not every day...
just \"periods\" when it manifests followed by periods where it is
completely absent).

That sounds like somebody switching a generating set on or off. It is a process that can generate transients.

The famous Telsa grid scale battery in South Australia is reputed to be fast enough to cancel that sort of transient really fast (and half it\'s capacity is devoted to doing just that, which made it a really profitable investment.

The other source of that kind of transient is lightning strikes in the wrong place. They are less predictable.

<snip>

--
Bill Sloman, Sydney

 

[Clifford Heath]

On 30/3/22 1:25 pm, Don Y wrote:

From time to time, we seem to experience a power \"glitch\", once a
day, at roughly the same time -- usually ~3AM.  (but, not every day...
just \"periods\" when it manifests followed by periods where it is
completely absent).

It\'s not a problem, for the most part, as everything is on UPSs, here
(the microwave oven seems to complain the most as it isn\'t on a UPS
and its damn clock often resets -- I long for the day when appliances
have synchronized clocks or NO clocks!!!)

I assume this is some sort of switching transient that affects the
entire city (?) -- or, at least large portions of it.

We had repeated trips of the whole-house RCD every few days for months.
Always at 7:58AM. ALWAYS. I turned off everything in the house that
could know the time of day, and they still happened. Eventually I became
certain that it was something to do with the power supply, and started
harassing our provider.

They kept fobbing me off, saying I should replace the RCD - which at the
time was brand-new, after a renovation where we got a new powerboard,
and I told them that and insisted.

Eventually they admitted that 7:58AM is when they switch in some large
PFC capacitors in preparation for inductive industrial loads coming
alive. I told them that it was therefore their problem, and they
arranged to send a couple of electricians around to fit a more tolerant
RCD, at no cost to me.

When the sparkies came, they said they had been doing *hundreds* like
this. And that\'s just for the households who figured it out, and
complained long and hard enough to wear down the power company.

This was in 2000, before we started fitting RCD breakers on every circuit.

Clifford Heath.

 

[Jeff Layman]

On 30/03/2022 03:25, Don Y wrote:

From time to time, we seem to experience a power \"glitch\", once a
day, at roughly the same time -- usually ~3AM. (but, not every day...
just \"periods\" when it manifests followed by periods where it is
completely absent).

It\'s not a problem, for the most part, as everything is on UPSs, here
(the microwave oven seems to complain the most as it isn\'t on a UPS
and its damn clock often resets -- I long for the day when appliances
have synchronized clocks or NO clocks!!!)

I assume this is some sort of switching transient that affects the
entire city (?) -- or, at least large portions of it.

(our services are below grade so not likely caused by something
physically interfering with the transmission lines)

I\'m turning my attention to the design of the power systems for
my current project and figure it would be prudent to put some
line-monitoring capabilities into it (if only to let it anticipate
such problems and plan ahead).

So, the questions are:
- how often to sample (to be able to catch transient events)
- maximum peak likely to be encountered

[Of course, I have to anticipate what the power conditions are
likely to be in other parts of the market (US consumer and,
separately, commercial/industrial) and not just rely on my own
observations.]

I\'m tempted to buy a line monitor just to see what they\'ve done
(in terms of hardware interface; the signal processing software
won\'t be a problem). Recommendations? (again, two/three different
markets, as above)

Just get a \'scope monitoring the line power supply. Point a video camera
(preferably with continuous time display) at the screen and record a few
minutes before and after 3am every day. You should be able to record the
spike and the exact time it appears. Even a webcam on a laptop might do
the job. The power supply company wouldn\'t be able to argue with that
sort of evidence.

3am seems a strange time for transients. Some sort of fairly regular
maintenance work at the generation station or distribution switching,
perhaps?

--

Jeff

 

[Jan Panteltje]

On a sunny day (Tue, 29 Mar 2022 19:25:13 -0700) it happened Don Y
<blockedofcourse@foo.invalid> wrote in <t20f2p$ob9$1@dont-email.me>:

From time to time, we seem to experience a power \"glitch\", once a
day, at roughly the same time -- usually ~3AM. (but, not every day...
just \"periods\" when it manifests followed by periods where it is
completely absent).

It\'s not a problem, for the most part, as everything is on UPSs, here
(the microwave oven seems to complain the most as it isn\'t on a UPS
and its damn clock often resets -- I long for the day when appliances
have synchronized clocks or NO clocks!!!)

I assume this is some sort of switching transient that affects the
entire city (?) -- or, at least large portions of it.

(our services are below grade so not likely caused by something
physically interfering with the transmission lines)

I\'m turning my attention to the design of the power systems for
my current project and figure it would be prudent to put some
line-monitoring capabilities into it (if only to let it anticipate
such problems and plan ahead).

So, the questions are:
- how often to sample (to be able to catch transient events)
- maximum peak likely to be encountered

[Of course, I have to anticipate what the power conditions are
likely to be in other parts of the market (US consumer and,
separately, commercial/industrial) and not just rely on my own
observations.]

I\'m tempted to buy a line monitor just to see what they\'ve done
(in terms of hardware interface; the signal processing software
won\'t be a problem). Recommendations? (again, two/three different
markets, as above)

The power network over here switches, sometimes 2 times a day, between networks it seems.
This causes a short (usually less than a second) power dip.
UPS takes care of that as far as computers go.
Laptop has its on battery and will run much longer,
For longer power failures (will keep watching satellite, radio, ham radio, etc)
I have now a 250 AH 12 V lifepo4 battery and a 2 kW 12V to 230V pure sinewave converter.
So if the UPS starts screaming when power goes for a longer time,
then it takes a few minutes to switch the big stuff to that setup manually.
Sure, the clock in the microwave will reset,,,,
Happened a few weeks back, 2 hours no power, neighbor came to ask \'Have you no power too?\'
Well, yes and no, I was just switching to the big battery.
Talk about clocks, last Sunday we went to summer time, had to adjust 13 clocks here
Sure hope they get rid of that shit twice a year

The lifepo4 can easily power a microwave or cooking plate, or the TV for a whole evening..

 

[Arie de Muijnck]

On 2022-03-30 09:18, Jeff Layman wrote:

Just get a \'scope monitoring the line power supply. Point a video camera
(preferably with continuous time display) at the screen and record a few
minutes before and after 3am every day. You should be able to record the
spike and the exact time it appears. Even a webcam on a laptop might do
the job. The power supply company wouldn\'t be able to argue with that
sort of evidence.

3am seems a strange time for transients. Some sort of fairly regular
maintenance work at the generation station or distribution switching,
perhaps?

Or better: use a low voltage transformer and a resistive attenuator,
then capture the 1Vpp waveform on the LINE IN audio channel of a laptop.
Capture and analyze using e.g. the free Audacity, it shows the waveform
nicely. Much easier than trying to find a transient on a video (even
when the scope did capture it - some scopes have a low acquisition frame
rate and may miss a spike completely).

Arie

 

[Don Y]

On 3/30/2022 12:18 AM, Jeff Layman wrote:

On 30/03/2022 03:25, Don Y wrote:
From time to time, we seem to experience a power \"glitch\", once a
day, at roughly the same time -- usually ~3AM. (but, not every day...
just \"periods\" when it manifests followed by periods where it is
completely absent).

It\'s not a problem, for the most part, as everything is on UPSs, here
(the microwave oven seems to complain the most as it isn\'t on a UPS
and its damn clock often resets -- I long for the day when appliances
have synchronized clocks or NO clocks!!!)

I assume this is some sort of switching transient that affects the
entire city (?) -- or, at least large portions of it.

(our services are below grade so not likely caused by something
physically interfering with the transmission lines)

I\'m turning my attention to the design of the power systems for
my current project and figure it would be prudent to put some
line-monitoring capabilities into it (if only to let it anticipate
such problems and plan ahead).

So, the questions are:
- how often to sample (to be able to catch transient events)
- maximum peak likely to be encountered

[Of course, I have to anticipate what the power conditions are
likely to be in other parts of the market (US consumer and,
separately, commercial/industrial) and not just rely on my own
observations.]

I\'m tempted to buy a line monitor just to see what they\'ve done
(in terms of hardware interface; the signal processing software
won\'t be a problem). Recommendations? (again, two/three different
markets, as above)

Just get a \'scope monitoring the line power supply. Point a video camera
(preferably with continuous time display) at the screen and record a few
minutes before and after 3am every day. You should be able to record the spike
and the exact time it appears. Even a webcam on a laptop might do the job. The
power supply company wouldn\'t be able to argue with that sort of evidence.

I\'m not particularly concerned with *my* experience:

It\'s not a problem, for the most part, as everything is on UPSs, here
(the microwave oven seems to complain the most as it isn\'t on a UPS
and its damn clock often resets -- I long for the day when appliances
have synchronized clocks or NO clocks!!!)

Rather, I\'m concerned with adding that monitoring capability to my
product so *it* can learn/know what the \"local\" power conditions happen
to be (it runs 24/7/365). This would help it decide how to adjust the
load and schedule processes in anticipation of (or after detection of)
outages.

For example, *real* outages, here, have been very infrequent. And, have
have always been the result of equipment outages: cable segment failures,
blown fuses in the neighborhood distribution station, etc. As these are
relatively small events, from the perspective of the utility company, (unlike
a storm knocking out power to a large portion of a town) they can be
addressed with a small crew dispatched in short order. In each case, our
outage has typically been less than ~6 hours (before they\'ve rerouted power
from \"the other end\" of the feed).

By contrast, when I lived in the midwest, we had outages pretty regularly
(6 or more each year) and they persisted for longer periods.

So, siting my device *here* it could opt to maintain power for a larger
portion of its componentry (it can selectively shed load) for a longer
period of time and still hope to have spare backup capacity. In the
midwest, it would have had to learn to impose deeper cuts as it expected
longer outages.

It also lets the size of the (battery) backup be an independent parameter
at the discretion of the owner instead of an implicit requirement of the
design. A deployment with a bigger load looks like a nominal deployment
with a smaller backup, etc.

[e.g., I have a ~2200W load that I can keep fully operational for ~2hrs.
Someone else might not want to make that investment -- or might have
a BIGGER load -- so the system needs to know how to make tradeoffs in
scheduling its load]

Finally, being able to guesstimate the likelihood of an outage, based on
past observations. For example, if power fails, returns and then fails,
again, you\'d be slow to reinstall load hoping instead, to let the power
supply divert power to RE-charging instead of the load (which you expect
to likely need to *shed*, again, RSN... when the followup outage strikes)

[This has been the pattern, here, with power coming back on-line. The
crews will initially diagnose the problem, restore power -- and have
the problem manifest, again, in short order (\"Hey, Bill, the short is
still there...\")]

I\'m hoping that by being able to *look* at the mains as they are powering
the system, that it might be able to make some deductions about the
possible cause (and duration) of the outage. Instead of being \"surprised\"
by each new event!

3am seems a strange time for transients. Some sort of fairly regular
maintenance work at the generation station or distribution switching, perhaps?

Dunno. As I can\'t tell how widespread the problem is (it just this
neighborhood? this side of town? etc.) or the system elements that
lie between me and the \"problem\", I can\'t guess as to its cause.
Is it something related to some other \"nearby\" power consumer and
not the supplier? <shrug>

The UPSs all claim it to be \"excessive rate of change\" (or something to
that effect... not \"dropped cycle\" or \"low line\" or...).

In parts of town with overhead distribution (which likely includes the
high tension feeding us... somewhere), I can see large \"switches\"
(but no idea as to how -- or why -- they are actuated/opened)

Again, the cause is likely out of my control (unless a local fault).
I just want to be able to observe it in more detail than \"gee, the
lights flickered\" or \"ooops! power is out!\"

Hence the question as to what the appropriate capabilities of that
data acquisition (sub)system...

 

[Mike Monett]

Arie de Muijnck <eternal.september@ademu.com> wrote:

On 2022-03-30 09:18, Jeff Layman wrote:

Just get a \'scope monitoring the line power supply. Point a video camera
(preferably with continuous time display) at the screen and record a few
minutes before and after 3am every day. You should be able to record the
spike and the exact time it appears. Even a webcam on a laptop might do
the job. The power supply company wouldn\'t be able to argue with that
sort of evidence.

3am seems a strange time for transients. Some sort of fairly regular
maintenance work at the generation station or distribution switching,
perhaps?


Or better: use a low voltage transformer and a resistive attenuator,
then capture the 1Vpp waveform on the LINE IN audio channel of a laptop.
Capture and analyze using e.g. the free Audacity, it shows the waveform
nicely. Much easier than trying to find a transient on a video (even
when the scope did capture it - some scopes have a low acquisition frame
rate and may miss a spike completely).

Arie

A transformer will have poor high frequency response and will filter out
sharp spikes. Better to use a 100:1 capacitive/resistive divider across the
AC line voltage. Verify the LINE IN audio channel is 600 ohms, then add a
600k across the top capacitor.

The neutral doesn\'t have to connect to the chassis of the computer. If you
do, it will likely blow any GFI breaker that is on the ac line. Use GND for
the return.


--
MRM

 

[John Walliker]

On Wednesday, 30 March 2022 at 12:09:14 UTC+1, Mike Monett wrote:

Arie de Muijnck <eternal....@ademu.com> wrote:

On 2022-03-30 09:18, Jeff Layman wrote:

Just get a \'scope monitoring the line power supply. Point a video camera
(preferably with continuous time display) at the screen and record a few
minutes before and after 3am every day. You should be able to record the
spike and the exact time it appears. Even a webcam on a laptop might do
the job. The power supply company wouldn\'t be able to argue with that
sort of evidence.

3am seems a strange time for transients. Some sort of fairly regular
maintenance work at the generation station or distribution switching,
perhaps?


Or better: use a low voltage transformer and a resistive attenuator,
then capture the 1Vpp waveform on the LINE IN audio channel of a laptop.
Capture and analyze using e.g. the free Audacity, it shows the waveform
nicely. Much easier than trying to find a transient on a video (even
when the scope did capture it - some scopes have a low acquisition frame
rate and may miss a spike completely).

Arie
A transformer will have poor high frequency response and will filter out
sharp spikes. Better to use a 100:1 capacitive/resistive divider across the
AC line voltage. Verify the LINE IN audio channel is 600 ohms, then add a
600k across the top capacitor.

The neutral doesn\'t have to connect to the chassis of the computer. If you
do, it will likely blow any GFI breaker that is on the ac line. Use GND for
the return.

But are sharp spikes likely to be a problem? Any product which has been
through regulatory testing will have demonstrated a good immunity to
large short spikes, so it is much more likely that dropouts will cause
problems.
A small transformer will respond to frequencies of many kHz, so that should
be enough. What will prevent it from measuring large spikes is core
saturation but there are several ways of minimising the effects of this
that have been discussed here in the past.
Most products, especially those with switched mode power supplies,
should survive dropouts of 10ms or less without any problems
due to energy storage in their input capacitors.

John

 

[Don Y]

On 3/30/2022 4:41 AM, John Walliker wrote:

On Wednesday, 30 March 2022 at 12:09:14 UTC+1, Mike Monett wrote:
Arie de Muijnck <eternal....@ademu.com> wrote:

On 2022-03-30 09:18, Jeff Layman wrote:

Just get a \'scope monitoring the line power supply. Point a video camera
(preferably with continuous time display) at the screen and record a few
minutes before and after 3am every day. You should be able to record the
spike and the exact time it appears. Even a webcam on a laptop might do
the job. The power supply company wouldn\'t be able to argue with that
sort of evidence.

3am seems a strange time for transients. Some sort of fairly regular
maintenance work at the generation station or distribution switching,
perhaps?


Or better: use a low voltage transformer and a resistive attenuator,
then capture the 1Vpp waveform on the LINE IN audio channel of a laptop.
Capture and analyze using e.g. the free Audacity, it shows the waveform
nicely. Much easier than trying to find a transient on a video (even
when the scope did capture it - some scopes have a low acquisition frame
rate and may miss a spike completely).

Arie
A transformer will have poor high frequency response and will filter out
sharp spikes. Better to use a 100:1 capacitive/resistive divider across the
AC line voltage. Verify the LINE IN audio channel is 600 ohms, then add a
600k across the top capacitor.

The neutral doesn\'t have to connect to the chassis of the computer. If you
do, it will likely blow any GFI breaker that is on the ac line. Use GND for
the return.

But are sharp spikes likely to be a problem? Any product which has been
through regulatory testing will have demonstrated a good immunity to
large short spikes, so it is much more likely that dropouts will cause
problems.

You\'ve missed the point of (my!) post. The goal isn\'t to \"protect\" the
device -- OBSERVING the line won\'t do anything to make the device more
resilient!

Rather, the goal is to try to understand the nature of the disturbance
in light of other, \"previously recorded (quantified)\" disturbances and
use that to predict what is likely to happen with the mains, \"soon\".

E.g., when our cable segments fail (each transformer is daisy-chained
to the next transformer down the line -- unlike \"taps\" on an overhead
distribution line), the center/current carrying conductor (it\'s a coax)
shorts to the \"shield\" (neutral/ground). As such, you would expect to
\"see\" this arcing event instead of a \"clean\" open.

You can imagine that power won\'t be coming back anytime soon in the
event of such an observation.

A drunk slamming into a pole (overhead supply) would likely exhibit
a different sort of \"failure event\".

A brownout, still different.

Etc. Unless you can claim that those \"details\" carry no information,
then one would want to preserve as much data as possible.

[I can detect an outage just by counting 60Hz cycles and \"timing out\"
in ~20ms; doesn\'t tell me anything other than \"power is out!\"]

I\'m not limited to just observations of the mains but can also factor in
*other* observations (e.g., it is summer and ACbrrr loading, on the network,
is high; or, it is winter and an ice-coated branch may have taken out
an overhead line)

A small transformer will respond to frequencies of many kHz, so that should
be enough. What will prevent it from measuring large spikes is core
saturation but there are several ways of minimising the effects of this
that have been discussed here in the past.
Most products, especially those with switched mode power supplies,
should survive dropouts of 10ms or less without any problems
due to energy storage in their input capacitors.

John

 

[John Walliker]

On Wednesday, 30 March 2022 at 13:12:48 UTC+1, Don Y wrote:

You\'ve missed the point of (my!) post. The goal isn\'t to \"protect\" the
device -- OBSERVING the line won\'t do anything to make the device more
resilient!

OK. I can see why measuring disturbances that won\'t affect your
devices could be useful. The question then becomes one of how
much measurement bandwidth and resolution is necessary to get
this unknown information and how best to acquire it and process it.
As you don\'t know what you are looking for about the only
bandwidth constraint is going to be the bandwidth of the power
transmission system subject to avoiding frequencies high enough
to have long-wave broadcast transmissions. That suggests an
upper frequency limit of maybe tens of kHz. Of course, arcing in
nearby wiring could have much higher frequency components.
Maybe its worth looking at how arc fault interrupters detect arcing?

John

 

[John Doe]

Don Y wrote:

From time to time, we seem to experience a power \"glitch\", once a
day, at roughly the same time -- usually ~3AM. (but, not every day...
just \"periods\" when it manifests followed by periods where it is
completely absent).

It\'s not a problem, for the most part, as everything is on UPSs, here
(the microwave oven seems to complain the most as it isn\'t on a UPS
and its damn clock often resets -- I long for the day when appliances
have synchronized clocks or NO clocks!!!)

For 10+ years, I have been using a Tripp Lite LC 1200 voltage regulator
instead of a UPS, that\'s overkill for my PC and peripherals but it probably
increases the protection against occasional dropouts. Seems to work great.
Other stuff blinks, but not my PC. And if it ever does turn off, not in at
least a year, it stays off instead of blinking back on.

It has proved to be better than messing with a battery.
If it clicks, I backup stuff. Never know!

It also helps monitor room/household voltage since it includes over/under
voltage LEDs.

 

[Bob Engelhardt]

On 3/30/2022 12:11 AM, Clifford Heath wrote:

We had repeated trips of the whole-house RCD every few days for months.
...

RCD - residual-current device or ground fault circuit interrupter (GFCI)

 

[Don Y]

On 3/30/2022 6:34 AM, John Walliker wrote:

On Wednesday, 30 March 2022 at 13:12:48 UTC+1, Don Y wrote:

You\'ve missed the point of (my!) post. The goal isn\'t to \"protect\" the
device -- OBSERVING the line won\'t do anything to make the device more
resilient!

OK. I can see why measuring disturbances that won\'t affect your
devices could be useful. The question then becomes one of how
much measurement bandwidth and resolution is necessary to get
this unknown information and how best to acquire it and process it.

There are a fair number of publications (research) that describe faults
in the transmission network (because the utilities have an interest
in minimizing these). How those are reflected *into* a \"point of
observation\" that *I* would easily monitor is an issue. (telling
me what\'s happening on the high-tension side of my local feed isn\'t
the same thing as telling me what I will see \"locally\")

As you don\'t know what you are looking for about the only
bandwidth constraint is going to be the bandwidth of the power
transmission system subject to avoiding frequencies high enough
to have long-wave broadcast transmissions. That suggests an
upper frequency limit of maybe tens of kHz.

But, that ignores:

Of course, arcing in
nearby wiring could have much higher frequency components.

....as well as other failures, noise sources, etc. E.g., a fault
in a large load that eventually takes out the local branch circuit
can be just as \"bad\" for your source of power as a system-wide
power failure.

Tens of Hz is enough to (quickly) detect *outages*. Will tens of
KHz be sufficient to differentiate between different line faults
and transients? How much wire do you assume separates the
observation from the fault?? <shrug>

[And, we\'ve not addressed the magnitude of the transients... 10X?
log scale?]

> Maybe its worth looking at how arc fault interrupters detect arcing?

That\'s a good idea. But, again, they are only looking for arcing and
not the general case of \"disturbances\"/line quality. E.g., in an
industrial setting, I\'d expect the mains to be a lot dirtier than
in a domestic setting. So, you\'d have to \"learn\" when that \"dirt\"
is significant and when it just has to be tolerated.

And, they are obviously targeting \"cheap\" detection methods; I\'m
not so constrained.

 

[John Larkin]

On Wed, 30 Mar 2022 07:22:43 GMT, Jan Panteltje
<pNaonStpealmtje@yahoo.com> wrote:

The power network over here switches, sometimes 2 times a day, between networks it seems.
This causes a short (usually less than a second) power dip.
UPS takes care of that as far as computers go.
Laptop has its on battery and will run much longer,

I\'d like to use a laptop for a control application in an unattended
location, instead of a big PC and a UPS. But a PC bios can usually be
set up to restart the PC after a hard power failure, and it seems like
laptops can\'t do that for some reason. I\'d love to find one that does.

--

If a man will begin with certainties, he shall end with doubts,
but if he will be content to begin with doubts he shall end in certainties.
Francis Bacon

 

[whit3rd]

On Tuesday, March 29, 2022 at 7:25:36 PM UTC-7, Don Y wrote:

I\'m turning my attention to the design of the power systems for
my current project and figure it would be prudent to put some
line-monitoring capabilities into it (if only to let it anticipate
such problems and plan ahead).

So, the questions are:
- how often to sample (to be able to catch transient events)
- maximum peak likely to be encountered

It\'s relatively important to have an average-AC-voltage measure,
because some wiring issues can be diagnosed that way; you\'d want to
sample rectified/filtered V at tenth second or so, but only log \'events\', not
keep all the data. There\'s a few percent variance allowable, of course.

Load changes and loose connections or lightning strikes, or
diurnal overvoltage because of xformer tap decisions could show up.
Sites vary, but expect 2kV for miliseconds, in case of lightning.

More important surges or loads will cause zero-cross timing shifts which
tie into odd clunks from motors, so I\'d think to log also any deviation from
\'normal\' 120 (or 100) zero crossings per second. Maybe store a few dozen
cycles before and after an \'event\', gives you an idea of the transient. Motor
starts without zero-voltage-switching have dimmed my lights and
several times rebooted a Linux box exactly when I hear the buzzsaw.

 

[whit3rd]

On Wednesday, March 30, 2022 at 12:27:44 PM UTC-7, John Larkin wrote:

I\'d like to use a laptop for a control application in an unattended
location, instead of a big PC and a UPS. But a PC bios can usually be
set up to restart the PC after a hard power failure, and it seems like
laptops can\'t do that for some reason. I\'d love to find one that does.

MacOS laptops can be scheduled for turn-on and/or off once a day, with
the \'energy saver\' settings. UPS connection sometimes adds options, too.

 

[John Larkin]

On Wed, 30 Mar 2022 16:08:04 -0700 (PDT), whit3rd <whit3rd@gmail.com>
wrote:

On Wednesday, March 30, 2022 at 12:27:44 PM UTC-7, John Larkin wrote:

I\'d like to use a laptop for a control application in an unattended
location, instead of a big PC and a UPS. But a PC bios can usually be
set up to restart the PC after a hard power failure, and it seems like
laptops can\'t do that for some reason. I\'d love to find one that does.

MacOS laptops can be scheduled for turn-on and/or off once a day, with
the \'energy saver\' settings. UPS connection sometimes adds options, too.

I need a Windows machine. If power fails for a full day maybe, a
laptop will run out of battery power and shut down, but can\'t be set
up to restart when power comes back. At least none that I can find.

Strange.

Maybe some laptops can be set up to deep-sleep when batteries get low,
but wake up when power comes back. If one could ride out a few days
that way on remaining battery power, it would be OK.



--

If a man will begin with certainties, he shall end with doubts,
but if he will be content to begin with doubts he shall end in certainties.
Francis Bacon

 

[Don Y]

On 3/30/2022 2:58 PM, whit3rd wrote:

So, the questions are:
- how often to sample (to be able to catch transient events)
- maximum peak likely to be encountered

It\'s relatively important to have an average-AC-voltage measure,
because some wiring issues can be diagnosed that way; you\'d want to
sample rectified/filtered V at tenth second or so, but only log \'events\', not
keep all the data. There\'s a few percent variance allowable, of course.

But those would be \"perform once\" types of calculations; the wiring
isn\'t likely to change \"dynamically\".

Load changes and loose connections or lightning strikes, or
diurnal overvoltage because of xformer tap decisions could show up.
Sites vary, but expect 2kV for miliseconds, in case of lightning.

OK. I assume we\'re still speaking of consumer deployments...

More important surges or loads will cause zero-cross timing shifts which
tie into odd clunks from motors, so I\'d think to log also any deviation from
\'normal\' 120 (or 100) zero crossings per second. Maybe store a few dozen
cycles before and after an \'event\', gives you an idea of the transient. Motor
starts without zero-voltage-switching have dimmed my lights and
several times rebooted a Linux box exactly when I hear the buzzsaw.

Hmmm... I hadn\'t thought of keeping much \"context\".

The FNET folks sample at ~1.5KHz (I don\'t recall the precision) and try to
detect anomalies in the grid by coordinating observations from geographically
dispersed measurement stations. I assume some of their algorithms could be
applied to local \"single observation\" points.

As long as the \"disturbance/transient\" doesn\'t affect (or predict!) power
availability (as seen at the output of MY power supply), I\'m likely not too
concerned with it. I can carry most of my (distributed) loads over short
durations, regardless of the investment a particular site may have made
in \"backup\" capability.

I\'d have to be more concerned about sites that power individual nodes
\"locally\" from PSUs that aren\'t as robust. I will know that this is
happening (*has* happened) and can take some measures to prevent loss
of functionality. E.g., don\'t dispatch processes to nodes that may
not have reliable power at a particular site. Or, force the OS to
checkpoint every process running on those nodes (which adds overhead).

Ideally, I\'d not want to take any prophylactic measures unless needed
as they translate into \"overhead\"/waste.

 

[bud--]

On 3/29/2022 10:11 PM, Clifford Heath wrote:

On 30/3/22 1:25 pm, Don Y wrote:
 From time to time, we seem to experience a power \"glitch\", once a
day, at roughly the same time -- usually ~3AM.  (but, not every day...
just \"periods\" when it manifests followed by periods where it is
completely absent).

It\'s not a problem, for the most part, as everything is on UPSs, here
(the microwave oven seems to complain the most as it isn\'t on a UPS
and its damn clock often resets -- I long for the day when appliances
have synchronized clocks or NO clocks!!!)

I assume this is some sort of switching transient that affects the
entire city (?) -- or, at least large portions of it.

We had repeated trips of the whole-house RCD every few days for months.
Always at 7:58AM. ALWAYS. I turned off everything in the house that
could know the time of day, and they still happened. Eventually I became
certain that it was something to do with the power supply, and started
harassing our provider.

They kept fobbing me off, saying I should replace the RCD - which at the
time was brand-new, after a renovation where we got a new powerboard,
and I told them that and insisted.

Eventually they admitted that 7:58AM is when they switch in some large
PFC capacitors in preparation for inductive industrial loads coming
alive. I told them that it was therefore their problem, and they
arranged to send a couple of electricians around to fit a more tolerant
RCD, at no cost to me.

When the sparkies came, they said they had been doing *hundreds* like
this. And that\'s just for the households who figured it out, and
complained long and hard enough to wear down the power company.

This was in 2000, before we started fitting RCD breakers on every circuit.

Clifford Heath.

Switching of power factor caps is a known potential cause of significant
surges. Would be interesting why that trips a RCD.