I visited the UK's largest on-shore wind farm this afternoon. Some of
the turbines were running and others were not. I assume this was
simply a factor of demand.

There was one turbine we watched (turbine 40). It was running as we
arrived, then it stopped, then it restarted (all as others in the same
section continued to run). Why would they stop and start one turbine?
Do they need to be rested or tested or rebooted periodically?

How do they maintain the frequency if the rotation speed can vary with
the wind? I know they can adjust the angle of the blades but it was
clear the turbines were not all running at the same speed.

On 11/10/2020 20:21, Scott wrote:
I visited the UK's largest on-shore wind farm this afternoon. Some of
the turbines were running and others were not. I assume this was
simply a factor of demand.

There was one turbine we watched (turbine 40). It was running as we
arrived, then it stopped, then it restarted (all as others in the same
section continued to run). Why would they stop and start one turbine?
Do they need to be rested or tested or rebooted periodically?

How do they maintain the frequency if the rotation speed can vary with
the wind? I know they can adjust the angle of the blades but it was
clear the turbines were not all running at the same speed.

There's one near me with only a dozen turbines.

I reckon there's one off more often than not. They aren't very reliable.

Frequency - AIUI generate DC, and use some clever electronics to get it
on the grid. Not quite clever enough though...

https://www.independent.co.uk/news/uk/home-news/uk-power-cut-cause-hornsea-wind-farm-little-barford-report-a9070886.html

Andy

Scott wrote:

How do they maintain the frequency if the rotation speed can vary with
the wind? I know they can adjust the angle of the blades but it was
clear the turbines were not all running at the same speed.

Presumably there are inverters actually feeding power onto the grid.

--
Chris Green
·

On Sun, 11 Oct 2020 21:50:41 +0100, Vir Campestris
wrote:

snip

Frequency - AIUI generate DC, and use some clever electronics to get it
on the grid. Not quite clever enough though...

I think we went to a small power station when I was at college doing
my HND in Electrical Engineering and I think they synched the
frequency of their output to that of the grid manually ... or hit the
big connection switch manually suggesting if they got it wrong by more
than a bit, it could rip the generators off their mounts?

Cheers, T i m

On 11/10/2020 20:21, Scott wrote:
I visited the UK's largest on-shore wind farm this afternoon. Some of
the turbines were running and others were not. I assume this was
simply a factor of demand.

There was one turbine we watched (turbine 40). It was running as we
arrived, then it stopped, then it restarted (all as others in the same
section continued to run). Why would they stop and start one turbine?
Do they need to be rested or tested or rebooted periodically?

How do they maintain the frequency if the rotation speed can vary with
the wind?

I would expect by using a grid tie inverter - i.e. they just slave
themselves to the incoming mains.

So there is no requirement to sync a rotating mass with the grid, which
makes it easier from their point of view (and presumably less use to the
grid)



--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

Scott wrote:
I visited the UK's largest on-shore wind farm this afternoon. Some of
the turbines were running and others were not. I assume this was
simply a factor of demand.

There was one turbine we watched (turbine 40). It was running as we
arrived, then it stopped, then it restarted (all as others in the same
section continued to run). Why would they stop and start one turbine?
Do they need to be rested or tested or rebooted periodically?

How do they maintain the frequency if the rotation speed can vary with
the wind? I know they can adjust the angle of the blades but it was
clear the turbines were not all running at the same speed.

https://www.lagerweywind.nl/wp-conte...LW_L147_en.pdf

GENERAL

Nominal power 4.3 MW
Rotor diameter 147 m
IEC class IIA

Turbine concept Direct drive, variable speed,
variable pitch, full power

Power control Electric pitch control

GENERATOR Lagerwey multi-pole
synchronous generator
Field generation Permanent magnet

Cooling Based on air flow around
the outside of generator
(cooling fins)

CONVERTER
Type Full power AC-DC-AC
Control system IGBT-Control
Cooling Water-cooled

OPERATIONAL DATA

Cut in wind speed 2.5 m/s
Cut out wind speed 25.0 m/s
Power factor Regulated

SAFETY SYSTEM 3 independent pitch control
systems with emergency
power provision

OTHER

Service brake system Standard
Lubrication system Automatically controlled
bearing and gear lubrication

The AC-DC-AC part, the output AC side matches the grid frequency.
The output side could be single-phase or three-phase, whatever
the customer wants.

Paul

One I remember had some clever kind of gearing that could be used to power
the generator even in light winds with the blades whizzing around and in
strong winds with them turning more slowly, but presumably giving more
torque. I never bothered to find out.
I'm sure there are many types with all sorts of clever gadgets to try to be
as efficient as possible. One worry though is local climate effects of such
devices. If you are taking power from the wind, then one assumes downwind of
the turbines the air is moving slower and with more turbulence as you often
get when high rise buildings are built in windy places.
Brian

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

Blind user, so no pictures please
Note this Signature is meaningless.!
"T i m" wrote in message
...
On Sun, 11 Oct 2020 21:50:41 +0100, Vir Campestris
wrote:

snip

Frequency - AIUI generate DC, and use some clever electronics to get it
on the grid. Not quite clever enough though...

I think we went to a small power station when I was at college doing
my HND in Electrical Engineering and I think they synched the
frequency of their output to that of the grid manually ... or hit the
big connection switch manually suggesting if they got it wrong by more
than a bit, it could rip the generators off their mounts?

Cheers, T i m

On 12/10/2020 09:00, Chris Hogg wrote:
On Mon, 12 Oct 2020 03:19:43 -0400, Paul
wrote:

Scott wrote:
I visited the UK's largest on-shore wind farm this afternoon. Some of
the turbines were running and others were not. I assume this was
simply a factor of demand.

There was one turbine we watched (turbine 40). It was running as we
arrived, then it stopped, then it restarted (all as others in the same
section continued to run). Why would they stop and start one turbine?
Do they need to be rested or tested or rebooted periodically?

How do they maintain the frequency if the rotation speed can vary with
the wind? I know they can adjust the angle of the blades but it was
clear the turbines were not all running at the same speed.

https://www.lagerweywind.nl/wp-conte...LW_L147_en.pdf

GENERAL

Nominal power 4.3 MW
Rotor diameter 147 m
IEC class IIA

Turbine concept Direct drive, variable speed,
variable pitch, full power

Power control Electric pitch control

GENERATOR Lagerwey multi-pole
synchronous generator
Field generation Permanent magnet

Cooling Based on air flow around
the outside of generator
(cooling fins)

CONVERTER
Type Full power AC-DC-AC
Control system IGBT-Control
Cooling Water-cooled

OPERATIONAL DATA

Cut in wind speed 2.5 m/s
Cut out wind speed 25.0 m/s
Power factor Regulated

SAFETY SYSTEM 3 independent pitch control
systems with emergency
power provision

OTHER

Service brake system Standard
Lubrication system Automatically controlled
bearing and gear lubrication

The AC-DC-AC part, the output AC side matches the grid frequency.
The output side could be single-phase or three-phase, whatever
the customer wants.

Paul

So, for the benefit of my understanding, they generate AC of variable
frequency depending on wind speed, rate of rotation etc. This is then
rectified to DC, which is then converted back to AC of frequency
corresponding to the grid frequency and locked in to it. Is that a
reasonable summary?

Yes.

All rotating generators are AC, and DC is obtained from them either by
mechanical rectification (commutators) or via silicon diodes.

Only constant speed turbines running at some sub-multiple of 50Hz (3000
rpm) can generate synchronous mains frequencies.

Wind turbines by their nature are not constant speed devices and
gearboxes to push than from a few revs per minute up to synchronous
speed would be lossy fragile and expensive. And locking their blades to
a constant speed would probably destroy them.

So its AC=DC=mains freq AC via two pieces of power electronics


--
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.

On 12/10/2020 09:06, Chris Hogg wrote:
On Mon, 12 Oct 2020 08:47:03 +0100, "Brian Gaff \(Sofa\)"
wrote:

If you are taking power from the wind, then one assumes downwind of
the turbines the air is moving slower and with more turbulence as you often
get when high rise buildings are built in windy places.
Brian

The down-wind effects of wind turbines can be significant.
https://tinyurl.com/y3ogwfmo

There are more scholarly articles out there. studies done to find best
'planting separations'

Obviously it depends on wind turbine cost versus land cost.


--
Any fool can believe in principles - and most of them do!

Chris Hogg wrote:
On Mon, 12 Oct 2020 03:19:43 -0400, Paul
wrote:

Scott wrote:
I visited the UK's largest on-shore wind farm this afternoon. Some of
the turbines were running and others were not. I assume this was
simply a factor of demand.

There was one turbine we watched (turbine 40). It was running as we
arrived, then it stopped, then it restarted (all as others in the same
section continued to run). Why would they stop and start one turbine?
Do they need to be rested or tested or rebooted periodically?

How do they maintain the frequency if the rotation speed can vary with
the wind? I know they can adjust the angle of the blades but it was
clear the turbines were not all running at the same speed.
https://www.lagerweywind.nl/wp-conte...LW_L147_en.pdf

GENERAL

Nominal power 4.3 MW
Rotor diameter 147 m
IEC class IIA

Turbine concept Direct drive, variable speed,
variable pitch, full power

Power control Electric pitch control

GENERATOR Lagerwey multi-pole
synchronous generator
Field generation Permanent magnet

Cooling Based on air flow around
the outside of generator
(cooling fins)

CONVERTER
Type Full power AC-DC-AC
Control system IGBT-Control
Cooling Water-cooled

OPERATIONAL DATA

Cut in wind speed 2.5 m/s
Cut out wind speed 25.0 m/s
Power factor Regulated

SAFETY SYSTEM 3 independent pitch control
systems with emergency
power provision

OTHER

Service brake system Standard
Lubrication system Automatically controlled
bearing and gear lubrication

The AC-DC-AC part, the output AC side matches the grid frequency.
The output side could be single-phase or three-phase, whatever
the customer wants.

Paul

So, for the benefit of my understanding, they generate AC of variable
frequency depending on wind speed, rate of rotation etc. This is then
rectified to DC, which is then converted back to AC of frequency
corresponding to the grid frequency and locked in to it. Is that a
reasonable summary?


Yes, that's it.

Just don't underestimate the complexity of that converter
though. It's got a lot to do, to prevent the tower
from toppling over, the blades from flying off, and so on.
Since the document above claims an ordinary "generator" with a
permanent magnet rotor is being used, there are some
dangerous conditions involved there if the generator
is under-loaded. Part of what the converter has to do
is "get rid of the energy with haste". Transferring
it to the grid, helps keep down the terminals voltage
on the generator part.

They could use a generator, an alternator, a magneto.
Each has different properties. On something like
this, maybe they're shooting for decent efficiency.
I don't know if the alternator is the best choice
for that. Your car uses an alternator, because
it's "dead easy to control". But it also happens
to run at a rather impressively high temperature.
Even generators get warm. That's why the 97% number
in that spec sheet is pretty amazing.

Paul

In message , T i m
writes
On Sun, 11 Oct 2020 21:50:41 +0100, Vir Campestris
wrote:

snip

Frequency - AIUI generate DC, and use some clever electronics to get it
on the grid. Not quite clever enough though...

I think we went to a small power station when I was at college doing
my HND in Electrical Engineering and I think they synched the
frequency of their output to that of the grid manually ... or hit the
big connection switch manually suggesting if they got it wrong by more
than a bit, it could rip the generators off their mounts?

Cheers, T i m

I did a fair amount of 'heavy current' electrical engineering at
university, and one of the lab experiments was to run up a large (and
fairly ancient) three-phase generator (driven by a DC motor) and
synchronise it with the mains.

Not only did you have to get the speed right, but (obviously) you had to
ensure that the three phases were correct. This was achieved by having a
lamp bulb across each of the contacts of the three-pole switch that
connected the three generator armature outputs to the mains. [I believe
the lamps were coloured red, blue and yellow.] As you approached
synchronous speed the fluctuations in their brightness would slow to a
stop - and when the brightness was at a minimum you then had to adjust
the generator field current to get the generator output voltage to
exactly match the mains voltage (when the lamps went out). Only then
could you throw the switch - and if there wasn't a big bang and a
grinding of metal you knew you had got the generator successfully locked
to the mains.

You then did various measurements about (for example) what happened when
you altered the drive power supplied by the DC motor and the amount of
generator field current. Again you had to be careful, because if you
varied things too far the system could unlock from the mains (with the
aforementioned spectacular results).

All this was pretty scary stuff, and these days I expect that the
operation of power stations is far more automated and foolproof than it
used to be.
--
Ian

On Mon, 12 Oct 2020 23:53:38 +0100, Ian Jackson
wrote:

snip

I think we went to a small power station when I was at college doing
my HND in Electrical Engineering and I think they synched the
frequency of their output to that of the grid manually ... or hit the
big connection switch manually suggesting if they got it wrong by more
than a bit, it could rip the generators off their mounts?


I did a fair amount of 'heavy current' electrical engineering at
university, and one of the lab experiments was to run up a large (and
fairly ancient) three-phase generator (driven by a DC motor) and
synchronise it with the mains.

Not only did you have to get the speed right,

Ah, so I did remember it correctly then. ;-)

but (obviously) you had to
ensure that the three phases were correct. This was achieved by having a
lamp bulb across each of the contacts of the three-pole switch that
connected the three generator armature outputs to the mains. [I believe
the lamps were coloured red, blue and yellow.] As you approached
synchronous speed the fluctuations in their brightness would slow to a
stop - and when the brightness was at a minimum you then had to adjust
the generator field current to get the generator output voltage to
exactly match the mains voltage (when the lamps went out). Only then
could you throw the switch -

Clever.

and if there wasn't a big bang and a
grinding of metal you knew you had got the generator successfully locked
to the mains.

;-)

You then did various measurements about (for example) what happened when
you altered the drive power supplied by the DC motor and the amount of
generator field current. Again you had to be careful, because if you
varied things too far the system could unlock from the mains (with the
aforementioned spectacular results).

Ooops. I must admit that I assumed once 'locked in' the grid would
override anything feeding it.

All this was pretty scary stuff, and these days I expect that the
operation of power stations is far more automated and foolproof than it
used to be.

Yeah. ;-(

I had quite a long telephone chat with a neighbour / mate last night
about batteries. He is a fairly competent wrench but not very
confident, tending to push most non basic jobs elsewhere.

He has an expensive eBike and because he was tending his wife (home
dialysis etc) he didn't get to use it, it was left 'too long' and the
battery pack died. After she passed away (and hence the length of the
chat last night, he has good days and bad days and that was a bad day)
he has had a big clear / sort out and dug out this bike and wanted to
do something with it.

I told him what to do re the battery (open it up, check the contents,
we can get replacement cells, how to test it etc) and he bottled it
and said he was going to send it off. I must have sounded a bit
dismayed (the battery pack wasn't 'worth £900', it was fcuked so worth
nothing and so he had little to lose by trying with my help etc) so he
started looking around and at tab spot welders and cell suppliers etc.

I gave him a small list of simple tools (watt meters, car headlamps
etc) / connectors and he's been getting them together and last night
was about how he would use such and what sort of current would you
need / get when you connected stuff up various ways (for testing the
bike's electrics, testing the BMS, running a capacity test on another
eBike he has etc) and so we ended up at Ohms law and how to use that
to calculate / predict the resistance of loads (alone with power etc).

Even silly things that why 'current' is measured in 'amps' and has the
symbol of 'I'. ;-)

I think I left him enthused (and distracted) and I'm looking forward
to the next batch of Whatsapp pictures as he puts more kit together.
;-)

Cheers, T i m