Last night, actually early hours of this morning, we were getting
multiple short power cuts but also one of our RCDs recurrently tripping
and a UPS switching to battery every few seconds for less than a second
even between observed power lossss. I didn't, owing to the hour and the
need to set up some sort of voltage divider, get to look at the supply
on an oscilloscope, but I think we can assume all was not well. The
actual voltage measured by the UPS remained at the usual 244-247.

This morning the voltage has dropped to 230-233 and the frequency to
49.8.

My question is how they do this, when Gridwatch confirms the national
frequency is a usual 50.1Hz? It is a rural, mid-Wales overhead supply.

--

Roger Hayter

Roger Hayter wrote:

This morning the voltage has dropped to 230-233 and the frequency to
49.8.

Maybe your area is running on a temporary genny, there's only one grid
frequency for the whole country ...

On 01/03/2020 09:42, Andy Burns wrote:
Roger Hayter wrote:

This morning the voltage has dropped to 230-233 and the frequency to
49.8.

Maybe your area is running on a temporary genny, there's only one grid
frequency for the whole country ...

Aha. That is something I hadn't considered.


--
The urge to save humanity is almost always a false front for the urge to
rule.
€“ H. L. Mencken, American journalist, 1880-1956

Andy Burns wrote:

Roger Hayter wrote:

This morning the voltage has dropped to 230-233 and the frequency to
49.8.

Maybe your area is running on a temporary genny, there's only one grid
frequency for the whole country ...

That, or the UPS being wrong, were the only things I could think of. I
can't see how even an overloaded distribution line could actually cause
a progressive phase shift like that. BTW, I meant 50.01Hz for the
national frequency, not 50.1 as I wrote.

--

Roger Hayter

On Sun, 1 Mar 2020 09:42:16 +0000, Andy Burns wrote:

This morning the voltage has dropped to 230-233 and the frequency
to
49.8.

Maybe your area is running on a temporary genny, there's only one grid
frequency for the whole country ...

How accurate is the frequency meter being used? I wouldn't trust the
UPS. My APC unit displays to two decimal places but measurement
increments are 0.25 Hz, logs only show 49.75 or 50.00 Hz...

I'd expect an actual power cut of at least several minutes to half an
hour to do all the SIDE stuff required to connect in a temporary
generator and again to disconnect it. Check your DNO's web site for
power cut information. I doubt they'd bung in a genset unless the
fault is going to take 12 hours to fix and affects a fair number of
customers.

Reduced voltage could simply be the result of changes in the local
distribution to isolate the fault and restore as many customers as
possible as quickly as possible. Done by manually opening/closeing
switches in the local distribution. With a "bumpy" supply all you're
likely to notice is the bumps stopping when they disconnect the
faulty section.

--
Cheers
Dave.

On 01/03/2020 10:38, Dave Liquorice wrote:
I doubt they'd bung in a genset unless the
fault is going to take 12 hours to fix and affects a fair number of
customers.
In fact only me and my neighbours, albeit in a bloody listed mansion -
were run off the genny when they put it in.

But it was 'out' for about a week while they dug up the 11kv
underground, and found a sharp stone through one of the phases.

A combination of bad installation and the farmers tractor going over the
top of it I suspect :-)


--
€œSome people like to travel by train because it combines the slowness of
a car with the cramped public exposure of €¨an airplane.€�

Dennis Miller

Yes I'm waiting to see what happens a bit away from here as they burried a
very large gas main under a farmers field some years ago now. grin.
Brian

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"The Natural Philosopher" wrote in message
...
On 01/03/2020 10:38, Dave Liquorice wrote:
I doubt they'd bung in a genset unless the
fault is going to take 12 hours to fix and affects a fair number of
customers.
In fact only me and my neighbours, albeit in a bloody listed mansion -
were run off the genny when they put it in.

But it was 'out' for about a week while they dug up the 11kv underground,
and found a sharp stone through one of the phases.

A combination of bad installation and the farmers tractor going over the
top of it I suspect :-)


--
"Some people like to travel by train because it combines the slowness of a
car with the cramped public exposure of ?an airplane."

Dennis Miller

In article l.net,
Dave Liquorice wrote:
On Sun, 1 Mar 2020 09:42:16 +0000, Andy Burns wrote:

This morning the voltage has dropped to 230-233 and the frequency
to
49.8.

Maybe your area is running on a temporary genny, there's only one grid
frequency for the whole country ...

How accurate is the frequency meter being used? I wouldn't trust the
UPS. My APC unit displays to two decimal places but measurement
increments are 0.25 Hz, logs only show 49.75 or 50.00 Hz...

I'd expect an actual power cut of at least several minutes to half an
hour to do all the SIDE stuff required to connect in a temporary
generator and again to disconnect it. Check your DNO's web site for
power cut information. I doubt they'd bung in a genset unless the
fault is going to take 12 hours to fix and affects a fair number of
customers.

we had a genset to ourselved when an underground cable fault took 5 houses
off,. Friday morning 3am Tuesday morning about 11am.

--
from KT24 in Surrey, England
"I'd rather die of exhaustion than die of boredom" Thomas Carlyle

On 01/03/2020 09:38, Roger Hayter wrote:
Last night, actually early hours of this morning, we were getting
multiple short power cuts but also one of our RCDs recurrently tripping
and a UPS switching to battery every few seconds for less than a second
even between observed power lossss. I didn't, owing to the hour and the
need to set up some sort of voltage divider, get to look at the supply
on an oscilloscope, but I think we can assume all was not well. The
actual voltage measured by the UPS remained at the usual 244-247.

This morning the voltage has dropped to 230-233 and the frequency to
49.8.

When was this? you can't change the frequency of the grid locally - the
whole nation is phase and frequency locked.

A UPS, on the other hand, can...

mysql select min(frequency) from day where timestamp like '2020-03-01%' ;
+----------------+
| min(frequency) |
+----------------+
| 49.849998 |
+----------------+
1 row in set (0.47 sec)

So yes at some point the frequency WAS that low. Let's see when

mysql select timestamp, frequency from day where timestamp like
'2020-03-01%' and frequency 49.90 ;
+---------------------+-----------+
| timestamp | frequency |
+---------------------+-----------+
| 2020-03-01 04:05:34 | 49.889 |
| 2020-03-01 04:35:34 | 49.882999 |
| 2020-03-01 04:40:35 | 49.849998 |
| 2020-03-01 05:55:38 | 49.875999 |
| 2020-03-01 06:20:34 | 49.889999 |
+---------------------+-----------+
5 rows in set (0.13 sec)


So at around 0400-0500 they let the frequency drop.

My question is how they do this, when Gridwatch confirms the national
frequency is a usual 50.1Hz? It is a rural, mid-Wales overhead supply.


there is no 'usual' frequency. Only an average value of 50.0000000Hz.

When I was off grid and being run from a massive container sized genny
whilst they fixed an 11KV problem outside my house, I got a lot more trips.

Instability on the mains will trip RCDS that are 'on the limit'

If you were actually measuring incoming voltage and not UPS output
voltage a high voltage indicates that there is less load on your local
area - that is fully consistent with 'wee small hours'

a low frequency merely means they pulled more capacity off the grid than
they should have done - in all probability a wind farm or two tripped
out and dropped off.

A cursory glance at gridwatch suggests they stopped importing so much
from France and Holland at that point and CCGT was practically all off.
That would have left very little in the way of short term frequency
control on the grid.


--
"A point of view can be a dangerous luxury when substituted for insight
and understanding".

Marshall McLuhan

The Natural Philosopher wrote:

On 01/03/2020 09:38, Roger Hayter wrote:
Last night, actually early hours of this morning, we were getting
multiple short power cuts but also one of our RCDs recurrently tripping
and a UPS switching to battery every few seconds for less than a second
even between observed power lossss. I didn't, owing to the hour and the
need to set up some sort of voltage divider, get to look at the supply
on an oscilloscope, but I think we can assume all was not well. The
actual voltage measured by the UPS remained at the usual 244-247.

This morning the voltage has dropped to 230-233 and the frequency to
49.8.

When was this? you can't change the frequency of the grid locally - the
whole nation is phase and frequency locked.

A UPS, on the other hand, can...

mysql select min(frequency) from day where timestamp like '2020-03-01%' ;
+----------------+
| min(frequency) |
+----------------+
| 49.849998 |
+----------------+
1 row in set (0.47 sec)

So yes at some point the frequency WAS that low. Let's see when

mysql select timestamp, frequency from day where timestamp like
'2020-03-01%' and frequency 49.90 ;
+---------------------+-----------+
| timestamp | frequency |
+---------------------+-----------+
| 2020-03-01 04:05:34 | 49.889 |
| 2020-03-01 04:35:34 | 49.882999 |
| 2020-03-01 04:40:35 | 49.849998 |
| 2020-03-01 05:55:38 | 49.875999 |
| 2020-03-01 06:20:34 | 49.889999 |
+---------------------+-----------+
5 rows in set (0.13 sec)


So at around 0400-0500 they let the frequency drop.

This was 06.00 approximately and your website said 50.01 at the same
time as the UPS (on line, on battery it does better) said 49.8Hz



My question is how they do this, when Gridwatch confirms the national
frequency is a usual 50.1Hz? It is a rural, mid-Wales overhead supply.


there is no 'usual' frequency. Only an average value of 50.0000000Hz.

When I was off grid and being run from a massive container sized genny
whilst they fixed an 11KV problem outside my house, I got a lot more trips.

Instability on the mains will trip RCDS that are 'on the limit'

If you were actually measuring incoming voltage and not UPS output
voltage a high voltage indicates that there is less load on your local
area - that is fully consistent with 'wee small hours'

The high voltage is the usual one, which appears fairly consistent and
well regulated. The low voltage this morning is unusual. As of now,
10.16hr, the frequency is 50.0Hz and the voltage still 10v low at
233.9.




a low frequency merely means they pulled more capacity off the grid than
they should have done - in all probability a wind farm or two tripped
out and dropped off.

A cursory glance at gridwatch suggests they stopped importing so much
from France and Holland at that point and CCGT was practically all off.
That would have left very little in the way of short term frequency
control on the grid.


--

Roger Hayter

On 01/03/2020 10:21, Roger Hayter wrote:
This was 06.00 approximately and your website said 50.01 at the same
time as the UPS (on line, on battery it does better) said 49.8Hz
Then you are not on the same line as the rest of the country.

I would imagine some overheads are down and its genny power till its
fixed. That would account for the nuisance trips as well

--
Of what good are dead warriors? €¦ Warriors are those who desire battle
more than peace. Those who seek battle despite peace. Those who thump
their spears on the ground and talk of honor. Those who leap high the
battle dance and dream of glory €¦ The good of dead warriors, Mother, is
that they are dead.
Sheri S Tepper: The Awakeners.

In article ,
The Natural Philosopher wrote:
On 01/03/2020 10:21, Roger Hayter wrote:
This was 06.00 approximately and your website said 50.01 at the same
time as the UPS (on line, on battery it does better) said 49.8Hz
Then you are not on the same line as the rest of the country.

I would imagine some overheads are down and its genny power till its
fixed. That would account for the nuisance trips as well

Possibly a local generation station was on your part of the network.

--
from KT24 in Surrey, England
"I'd rather die of exhaustion than die of boredom" Thomas Carlyle

charles wrote:

In article ,
The Natural Philosopher wrote:
On 01/03/2020 10:21, Roger Hayter wrote:
This was 06.00 approximately and your website said 50.01 at the same
time as the UPS (on line, on battery it does better) said 49.8Hz
Then you are not on the same line as the rest of the country.

I would imagine some overheads are down and its genny power till its
fixed. That would account for the nuisance trips as well

Possibly a local generation station was on your part of the network.

I suppose it is possible but it would have to be a large and distant
fault.
The frequency has generally been 50.0 since mid morning but the voltage
has fallen to 221.5v. It doesn't normally fall more than a volt or two
fo about 242v at peak time.
There are reports of incident tape across the entrance to our nearest
substation where the 11kV is probably distributed (because they tend to
report work there when it fails) so perhaps it is flooded.

--

Roger Hayter

On Sunday, 1 March 2020 09:38:34 UTC, Roger Hayter wrote:
Last night, actually early hours of this morning, we were getting
multiple short power cuts but also one of our RCDs recurrently tripping
and a UPS switching to battery every few seconds for less than a second
even between observed power lossss. I didn't, owing to the hour and the
need to set up some sort of voltage divider, get to look at the supply
on an oscilloscope, but I think we can assume all was not well. The
actual voltage measured by the UPS remained at the usual 244-247.

This morning the voltage has dropped to 230-233 and the frequency to
49.8.

My question is how they do this, when Gridwatch confirms the national
frequency is a usual 50.1Hz? It is a rural, mid-Wales overhead supply.

When I looked a Gridwatch last night, it was around 50.25 Hz. Don't actually remember ever seeing it that high before. (Not that I look that often.)

On 01/03/2020 09:57, polygonum_on_google wrote:
On Sunday, 1 March 2020 09:38:34 UTC, Roger Hayter wrote:
Last night, actually early hours of this morning, we were getting
multiple short power cuts but also one of our RCDs recurrently tripping
and a UPS switching to battery every few seconds for less than a second
even between observed power lossss. I didn't, owing to the hour and the
need to set up some sort of voltage divider, get to look at the supply
on an oscilloscope, but I think we can assume all was not well. The
actual voltage measured by the UPS remained at the usual 244-247.

This morning the voltage has dropped to 230-233 and the frequency to
49.8.

My question is how they do this, when Gridwatch confirms the national
frequency is a usual 50.1Hz? It is a rural, mid-Wales overhead supply.

When I looked a Gridwatch last night, it was around 50.25 Hz. Don't actually remember ever seeing it that high before. (Not that I look that often.)

No, it wasn't that high last night

mysql select timestamp, frequency from day where timestamp
'2020-02-29' and frequency 50.15 ;
+---------------------+-----------+
| timestamp | frequency |
+---------------------+-----------+
| 2020-02-29 03:00:35 | 50.196999 |
| 2020-02-29 09:40:34 | 50.150002 |
| 2020-02-29 17:35:35 | 50.161999 |
| 2020-02-29 23:30:34 | 50.155998 |
| 2020-03-01 08:30:38 | 50.165001 |
+---------------------+-----------+
5 rows in set (0.00 sec)


--
The urge to save humanity is almost always a false front for the urge to
rule.
€“ H. L. Mencken, American journalist, 1880-1956

Sounds like the grid is not all one grid then, or that would cause some
issues. This problem came up twice in my lifetime, during the very cold
winter of 1963, and during the miners strike with rolling power cuts, but
the stress even then drove the cycles down.
Brian

--
----- --
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

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Note this Signature is meaningless.!
"Roger Hayter" wrote in message
...
Last night, actually early hours of this morning, we were getting
multiple short power cuts but also one of our RCDs recurrently tripping
and a UPS switching to battery every few seconds for less than a second
even between observed power lossss. I didn't, owing to the hour and the
need to set up some sort of voltage divider, get to look at the supply
on an oscilloscope, but I think we can assume all was not well. The
actual voltage measured by the UPS remained at the usual 244-247.

This morning the voltage has dropped to 230-233 and the frequency to
49.8.

My question is how they do this, when Gridwatch confirms the national
frequency is a usual 50.1Hz? It is a rural, mid-Wales overhead supply.

--

Roger Hayter