Why do street lights flicker in snowy weather?

[lurch]

Doesn't that sort of thing happen when intermittent shorting or arcing
trips a breaker somewhere and the breaker makes automatic re-tries ?

Derek.

I would describe such events as a bit more than a flickering.

 

[Tzortzakakis Dimitrios]

-----------------------------
Please check the definitions of demand and capacity - as the above is
nonsense.

Ideally the capacity should exceed the demand by some optimal margin but
as adding and dropping on line capacity is in blocks corresponding to the
capacity or rating of individual generators, and demand is up to the
customers (predictable but not controllable) the capacity will normally
exceed the demand by a fairly large margin at times- there is no
"stability" problem. As for waste by having extra on-line generation-
economic dispatch optimization is a common procedure.
If demand exceeds capacity, then problems can occur- not necessarily
stability problems.
As for the wind turbine reserve, you are being a bit over optimistic.
You are assuming 30% availability of wind capacity. In practice, from
recent data it appears that 10-15% is a better figure and this is a
statistic based on an annual average, which means nothing if wind fails.
In other words. reserve capacity must be available for the worst case
situation- 100% failure of any generation source, concentrated as in a
500MVA fossil plant or distributed as in 500-1MVA wind units in a region
where wind diversity is small.

*plonk*

 

[Steve Firth]

*plonk*

Excellent eco-weeny response there. Stick your fingers in your ears and
refuse to listen to hard fact.

 

[Steve Firth]

What would you expect from someone original enough
to give his name and address as noone@nospam?

The refutation of his, and any windmill enthusiast's claim that windmill
are going to reduce CO2 emissions is to look at countries which have an
aggressive policy of installing windmills. Say Germany.

Compare Germany (lot so windmills) to France (very few windmills, lots
of nuclear power). Germany emits about 10 tonnes of CO2 per person per
year. France about 6.5 tonnes per person per year.

Similar levels of industrialisation, similar climates, similar
everything. What the Germans have found (surprise, surprise) is that
wind power is unreliable and must be supplemented by conventional
generating capacity.

The UK could meet all its Kyoto obligations by going nuclear to the same
extent as France. Politicians in the UK are too wet to go for it.

 

[Steve Firth]

British citizens nowadays carry drugs into China

I know this is going to be hard for you to understand. But the use of
the plural in that phrase was inappropriate, and the use of "citizen" is
dubious. I think the term you were looking for was "subject", singular.

to get themselves executed;

I think you will find his aim was to make lots of money, not to get
executed.

they have good ol' Gaelic, Cymru or Anglo-Saxon
names like "Akmal Shaikh".

As opposed to good old American names like "Nidal Malik Hasan",
"Mohammed Ali", "Barak Obama" or "Androcles" you mean?

I'm surprised Gordon Brown isn't wearing a turban to get himself
re-elected.

Turbans are worn by a very small proportion of the UK population,
notably Sikhs who are not Moslems and who are not even the majority in
the immigrant population. Your own coutnry appears to have an immigrant
population of about 250 million. So if you're one of those tossers who
bases their entire politics on the status of someone as "an immigrant"
then I suspect you'll have to start by hating yourself.

Oh look. You already do.

 

[Steve Firth]

I know this is going to be hard for you to understand, but Britain has
citizens that are not subjects.

Mr Shaikh was a subject. Perhaps you should try to remember what you are
talking about?

I see you dodged away from the fact that he was an individual, not a
group. Is coping with the difference between singular and plural
something that confuses you?

 

[Steve Firth]

Oh look. You already have.

Shouldn't you be busy cutting holes in your bedsheet now?

BTW, only fuckwits piss about with follow-ups.

 

[daestrom]

*plonk*

Sigh... too bad.

Don's quite right on the matter. 'Capacity' is not the current
production, but the current maximum possible by on-line equipment. So
it is always kept greater than demand. 'Production' is matched to
demand by a variety of techniques. Most notably, manual operation of
base load settings and governors of regulating units.

'Spinning reserve' is kept on line to respond to sudden losses in
capacity by a unit trip. Most system operators are required to maintain
enough spinning reserve available for the tripping/loss of the largest
generating unit. So if the system has a very large unit on line (say,
1000 MW), they must have at least that much spinning reserve. So you
could say the system has a 'capacity' that is kept 1000 MW higher than
demand.

daestrom

 

[Archimedes' Lever]

What would you expect from someone original enough
to give his name and address as noone@nospam?

You are both fucking retarded.

 

[UltimatePatriot]

appears to have an immigrant
population of about 250 million.

You're an idiot.

 

[UltimatePatriot]

Shouldn't you be busy cutting holes in your bedsheet now?

BTW, only fuckwits piss about with follow-ups.

And only total retards piss and moan about the construction of a post
instead of the message posted.

You are one such total retard. In fact, you take the fucking cake,
retard boy.

 

[Archimedes' Lever]

Sigh... too bad.

Don's quite right on the matter. 'Capacity' is not the current
production, but the current maximum possible by on-line equipment. So
it is always kept greater than demand. 'Production' is matched to
demand by a variety of techniques. Most notably, manual operation of
base load settings and governors of regulating units.

'Spinning reserve' is kept on line to respond to sudden losses in
capacity by a unit trip. Most system operators are required to maintain
enough spinning reserve available for the tripping/loss of the largest
generating unit. So if the system has a very large unit on line (say,
1000 MW), they must have at least that much spinning reserve. So you
could say the system has a 'capacity' that is kept 1000 MW higher than
demand.

daestrom

This is absolutely correct.

 

[Tzortzakakis Dimitrios]

Excellent eco-weeny response there. Stick your fingers in your ears and
refuse to listen to hard fact. The plonk went to:
Please check the definitions of demand and capacity - as the above is
nonsense.

This is an attack ad hominem. I should check the definitions? Nobody forces
me to read plain insults.

 

[Tzortzakakis Dimitrios]

What would you expect from someone original enough
to give his name and address as noone@nospam?

If you read my signature, at the bottom is my real email address. So far,
almost nobody from any newsgroups have sent me a direct email (except a
couple of people), and I've been posting since 1999.

 

[Tzortzakakis Dimitrios]

Sigh... too bad.

Don's quite right on the matter. 'Capacity' is not the current
production, but the current maximum possible by on-line equipment.

Generating capacity, maybe?
I think it's installed power. I might be wrong, of course (since many people
seem to forget) I am greek and have gotten my degree in Greece. My English
is acceptable, but only God is always right.OTOH, we mere mortals...

So it is always kept greater than demand. 'Production' is matched to
demand by a variety of techniques. Most notably, manual operation of base
load settings and governors of regulating units.

As long as base units are synchronised, their most efficient use is to
operate 24/7 at full load. When they need to reduce output at night, they
might eg reduce coal supply

'Spinning reserve' is kept on line to respond to sudden losses in capacity
by a unit trip. Most system operators are required to maintain enough
spinning reserve available for the tripping/loss of the largest generating
unit. So if the system has a very large unit on line (say, 1000 MW), they
must have at least that much spinning reserve. So you could say the
system has a 'capacity' that is kept 1000 MW higher than demand.

Here, in Crete, we have fast units (gas turbines) that synchronise in 11-12
mins. Even the (small) steam units, 3-4 hours and the 2-stroke diesels 1/2
an hour. I think hydro can synchronise in quite fast, too.

 

[Archimedes' Lever]

No it's not. You don't appear to understand the term "ad hominem".


Yes. If you're going to pontificate about something which can be
measured objectively then you would do well to check your sources before
you start to talk about the subject. Otherwise you could end up looking
like someone who doesn't know what he's talking about. You were being
given good advice which you respond to like a child throwing a rattle
out of a pram.


No one posted an insult, plain or flowery. No one can force you to read
anything. You chose to read the post, you chose to flounce.

"eco-weeny" and "nonsense". The first IS an ad hominem insult, and the
second is not, but is, however a mild insult.

Anyone anywhere in the entire world that uses the Thompson retard's
"weeny" moniker for anything, is himself a maturity "weeny", or an
immaturity champion, take your pick, asswipe.

 

[daestrom]

Generating capacity, maybe?
I think it's installed power. I might be wrong, of course (since many people
seem to forget) I am greek and have gotten my degree in Greece. My English
is acceptable, but only God is always right.OTOH, we mere mortals...

I thought this might be the root of the issue. You are normally quite
knowledgeable about such matters. I wondered why you went for 'plonk'
so quickly on Don's post.

As long as base units are synchronised, their most efficient use is to
operate 24/7 at full load. When they need to reduce output at night, they
might eg reduce coal supply

Although it might be the most economic operating point for a single
plant, demand of course does not change in such increments. So some
units operate as 'regulating units' and must 'throttle' their output to
match demand.

As Don pointed out, in a traditional system a technique called 'economic
dispatch' is used to decide which plants to control in this way.
Typically this works out to those with the highest fuel costs. Plants
with the lowest marginal cost are kept on line as long as possible as
demand drops, and those with higher marginal costs are the first to cut
back or be taken off completely.

Of course the choice to leave a plant on line at very low power or shut
it down completely is another issue. Cost / time to re-start, expected
schedule for re-start and fixed operating costs to name a considerations.

In an unregulated system, the choice is made simply on the bid price of
each generator (not counting long-term purchase agreements).

Here, in Crete, we have fast units (gas turbines) that synchronise in 11-12
mins. Even the (small) steam units, 3-4 hours and the 2-stroke diesels 1/2
an hour. I think hydro can synchronise in quite fast, too.

Yes, we have 'peaking plants' that can be remotely started and
auto-synch and load in a matter of minutes (gas turbine or diesel). And
some plants schedule up/down based on predictions of demand.

But if you've lost a large plant's output due to a trip, even 10 minutes
is too slow. Every moment that demand exceeds actual production means
frequency is dropping. So the combination of the on-line spinning
reserve units and the excess capacity in regulating units (sometimes
counted in the 'spinning reserve' summary) has to respond within seconds.

Here in the US the FERC (Federal Energy Regulatory Commission), along
with NERC, has specific guidelines / requirements to maintain a certain
level of reliability in the transmission system. This

daestrom

 

[Guest]

This is an attack ad hominem. I should check the definitions? Nobody
forces me to read plain insults.


--
Tzortzakakis Dimitrios
major in electrical engineering
mechanized infantry reservist
hordad AT otenet DOT gr

----
And how do you define demand and capacity? Please tell me.
I know the usual definitions of these as applied to a power system and these
don't coincide with your usage of the terms. Hence my statement which was
not intended to be personal.

I did not mean to insult you but it is true that I couldn't make sense out
of your statements- possibly it is a language usage problem.

 

[Guest]

Generating capacity, maybe?
I think it's installed power. I might be wrong, of course (since many
people seem to forget) I am greek and have gotten my degree in Greece. My
English is acceptable, but only God is always right.OTOH, we mere
mortals...
As long as base units are synchronised, their most efficient use is to
operate 24/7 at full load. When they need to reduce output at night, they
might eg reduce coal supply

------------------
That is rarely the most efficient situation. In Crete, it may be the best
approach because you may have some large fossil units and, apparently some
hydro and the rest is high fuel cost gas turbines and diesels so that it
is sensible. Since the 1930's the process of economic dispatch at any load
is to load all generators on line (where possible) to the point of equal
incremental cost per Kw modified for losses. This was first done
intuitively by operators and later proved to be the optimum loading
distribution. A further and more complex addition is to optimize unit
commitment considering the costs of shutdown and restart of units.

Here, in Crete, we have fast units (gas turbines) that synchronise in
11-12 mins. Even the (small) steam units, 3-4 hours and the 2-stroke
diesels 1/2 an hour. I think hydro can synchronise in quite fast, too.

-------------
That's right but if you lose a major generation, do you simply drop loads
and wait for more generation to come on line or do you have enough reserve
capacity in on-line units to pick up the load if, for example, the largest
unit on the system fails?

I would suggest that capacity is not installed power but the available
power that can be generated by the units which are on-line. If you bring up
and synchronize a100MW machine, you have then increased on-line capacity by
100MW.

 

[Don Klipstein]

You are both fucking retarded.

I have known how you (via many nyms) like to resort to 5th-grade
name-calling in sci.electronics.design. As in calling people "retarded"
or "retards", and calling ideas "retarded".

And now you bring that sort of rubbish into the more genteel group
sci.engr.lighting?

Here, the harshest most-impolite phrase that I sense to play fairly well
in describing the $#!++iest piece of $#!+ is "stool specimen".

Heck, I have read about 98-99% of postings in sci.engr.lighting since
spring 1995, and I think yours is the first here since back then calling
people "fucking retarded". (Copied-pasted - I refuse to be the first
"regular" here to type such.)

Have a good day,

- Don Klipstein ([email protected])