"Roger Mills" wrote in message
...
In an earlier contribution to this discussion,
The Wanderer wrote:

Their *requirements* about standby generators are ensuring that if the
generator is to be used on an installation connected to the supplier's
distribution network there is no possibility of the generator
back-feeding into said distribution network, and that the earthing
arrangements for the generator meet, or perhaps more importantly,
don't compromise, PME approval where appropriate.


As a bit of an aside, I believe there are some systems - using wind and/or
solar power etc. - where you can feed surplus power into the grid and
'sell' it back to your electricity company. What happens in the event of a
power cut - does there have to be some mechanisn to prevent back-feeding
under such circumstances?
--

Was wondering this myself. The guide to the 16th ed regs say that you need
to have an isolation switch for a parallel supply which is accessible to the
supply company at all times. Perhaps they have a record of people which
such systems and go round and turn them off manually - but seems like a lot
of effort!

In an earlier contribution to this discussion,
Piers Finlayson wrote:

"Roger Mills" wrote in message
...

As a bit of an aside, I believe there are some systems - using wind
and/or solar power etc. - where you can feed surplus power into the
grid and 'sell' it back to your electricity company. What happens in
the event of a power cut - does there have to be some mechanisn to
prevent back-feeding under such circumstances?


Was wondering this myself. The guide to the 16th ed regs say that
you need to have an isolation switch for a parallel supply which is
accessible to the supply company at all times. Perhaps they have a
record of people which such systems and go round and turn them off
manually - but seems like a lot of effort!

I'm not sure whether you could do it with some sort of contactor, which
automatically dropped out if the mains failed. It would have to be able to
tell the difference between the real mains and your locally generated
'mains' - and I don't know whether it could.
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!

"Roger Mills" wrote in message
...
In an earlier contribution to this discussion,
Piers Finlayson wrote:

"Roger Mills" wrote in message
...

As a bit of an aside, I believe there are some systems - using wind
and/or solar power etc. - where you can feed surplus power into the
grid and 'sell' it back to your electricity company. What happens in
the event of a power cut - does there have to be some mechanisn to
prevent back-feeding under such circumstances?


Was wondering this myself. The guide to the 16th ed regs say that
you need to have an isolation switch for a parallel supply which is
accessible to the supply company at all times. Perhaps they have a
record of people which such systems and go round and turn them off
manually - but seems like a lot of effort!

I'm not sure whether you could do it with some sort of contactor, which
automatically dropped out if the mains failed. It would have to be able to
tell the difference between the real mains and your locally generated
'mains' - and I don't know whether it could.

But there must ber some kind of import / export metering.
That would know.

Hmmm...
How does import / export metering work?

I've managed to get my head all confused now. Thanks, guys!
Here's my problem...

I have a pair of wires, carrying AC power from a generator to a load.
So current flows in one direction, and then the other, alternating 50 times
a second. The magnitude of the current is a function of the voltage and
load. ( lets just stick with resistive loads for now. )

Now, I stick a black box in the middle.
4 terminals. 2 wires in, 2 wires out.

How can that box determine the direction of energy flow?
Clearly, energy is moving from the generator to the load.
But electrically, how can I determine the direction of energy ?
The box can measure direction of current, but that does not help.


--
Ron

"Ron Lowe" ronATlowe-famlyDOTmeDOTukSPURIOUS wrote in message
...
"Roger Mills" wrote in message
...
In an earlier contribution to this discussion,
Piers Finlayson wrote:

"Roger Mills" wrote in message
...

As a bit of an aside, I believe there are some systems - using wind
and/or solar power etc. - where you can feed surplus power into the
grid and 'sell' it back to your electricity company. What happens in
the event of a power cut - does there have to be some mechanisn to
prevent back-feeding under such circumstances?


Was wondering this myself. The guide to the 16th ed regs say that
you need to have an isolation switch for a parallel supply which is
accessible to the supply company at all times. Perhaps they have a
record of people which such systems and go round and turn them off
manually - but seems like a lot of effort!

I'm not sure whether you could do it with some sort of contactor, which
automatically dropped out if the mains failed. It would have to be able
to tell the difference between the real mains and your locally generated
'mains' - and I don't know whether it could.

But there must ber some kind of import / export metering.
That would know.

Hmmm...
How does import / export metering work?

I've managed to get my head all confused now. Thanks, guys!
Here's my problem...

I have a pair of wires, carrying AC power from a generator to a load.
So current flows in one direction, and then the other, alternating 50
times a second. The magnitude of the current is a function of the
voltage and load. ( lets just stick with resistive loads for now. )

Now, I stick a black box in the middle.
4 terminals. 2 wires in, 2 wires out.

How can that box determine the direction of energy flow?
Clearly, energy is moving from the generator to the load.
But electrically, how can I determine the direction of energy ?
The box can measure direction of current, but that does not help.


I guess it must be to do with the phase relationship between the voltage
and current.

The generator and grid are in voltage phase ( Remembers EE lecture 20 years
ago...the grid,being infinite bus bars, will hold the generator in sync ).

When the grid supplies energy to the consumer, the current in the L will be
towards the consumer whilst the V is +ve. ( resistive load ).

When the consumer supplies energy to the grid, the current in the L will be
towards the grid when the V is +ve.

Needs further thought for 3ph, but principle probably applies.

--
Ron

In article , Roger Mills
scribeth thus
In an earlier contribution to this discussion,
Piers Finlayson wrote:

"Roger Mills" wrote in message
...

As a bit of an aside, I believe there are some systems - using wind
and/or solar power etc. - where you can feed surplus power into the
grid and 'sell' it back to your electricity company. What happens in
the event of a power cut - does there have to be some mechanisn to
prevent back-feeding under such circumstances?


Was wondering this myself. The guide to the 16th ed regs say that
you need to have an isolation switch for a parallel supply which is
accessible to the supply company at all times. Perhaps they have a
record of people which such systems and go round and turn them off
manually - but seems like a lot of effort!

I'm not sure whether you could do it with some sort of contactor, which
automatically dropped out if the mains failed. It would have to be able to
tell the difference between the real mains and your locally generated
'mains' - and I don't know whether it could.


I think theres seems to be some confusion here between geniis that
provide standby power in case of mains fail, and that requires a
changeover isolating switch so that gennie cannot be connected to the
mains so as to backfeed it..

The other is where your generation feeds into the mains like say a wind
farm..

Begs an interesting question suppose theres a fault on a HV 11 kV local
network where one of theses is feeding back, or just the one turbine
like that have at the dogs home near Godmanchester how does that -know-
when the local system is down when its feeding into the supply?....
--
Tony Sayer

In article ,
tony sayer writes:
I think theres seems to be some confusion here between geniis that
provide standby power in case of mains fail, and that requires a
changeover isolating switch so that gennie cannot be connected to the
mains so as to backfeed it..

The other is where your generation feeds into the mains like say a wind
farm..

Begs an interesting question suppose theres a fault on a HV 11 kV local
network where one of theses is feeding back, or just the one turbine
like that have at the dogs home near Godmanchester how does that -know-
when the local system is down when its feeding into the supply?....

They are required to detect loss of mains supply and immediately
cease generation. I suspect this is done by the part of the circuit
that monitors the mains phase and synchronises the inverter output
with it.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

In an earlier contribution to this discussion,
tony sayer wrote:

In article , Roger Mills
scribeth thus
In an earlier contribution to this discussion,
Piers Finlayson wrote:

"Roger Mills" wrote in message
...

As a bit of an aside, I believe there are some systems - using wind
and/or solar power etc. - where you can feed surplus power into the
grid and 'sell' it back to your electricity company. What happens
in the event of a power cut - does there have to be some mechanisn
to prevent back-feeding under such circumstances?


Was wondering this myself. The guide to the 16th ed regs say that
you need to have an isolation switch for a parallel supply which is
accessible to the supply company at all times. Perhaps they have a
record of people which such systems and go round and turn them off
manually - but seems like a lot of effort!

I'm not sure whether you could do it with some sort of contactor,
which automatically dropped out if the mains failed. It would have
to be able to tell the difference between the real mains and your
locally generated 'mains' - and I don't know whether it could.


I think theres seems to be some confusion here between geniis that
provide standby power in case of mains fail, and that requires a
changeover isolating switch so that gennie cannot be connected to the
mains so as to backfeed it..

The other is where your generation feeds into the mains like say a
wind farm..

No, there's no confusion - I know they're not quite the same - which is why
I introduced it as "an aside".

Begs an interesting question suppose theres a fault on a HV 11 kV
local network where one of theses is feeding back, or just the one
turbine like that have at the dogs home near Godmanchester how does
that -know- when the local system is down when its feeding into the
supply?....

The precisely the question I and others have been asking above - but Andrew
G seems to have come up with a possible answer to it.
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!

On Sat, 2 Feb 2008 10:54:44 +0000, Steve Firth wrote:

And anyone buying a generator for standby use should run it from time to
time.

And put a decent load on it for an hour or so rather than just start it
let it run for 30 seconds then put it away again.

--
Cheers
Dave.

The Wanderer wrote:

cut - does there have to be some mechanisn to prevent back-feeding under
such circumstances?

'Fraid I don't know the answer to that one, but I would imagine so.

Yes, it's a legal requirement in the ESQCR:
quote
Parallel operation
22. - (1) Without prejudice to regulation 21, no person shall
install or operate a source of energy which may be connected in parallel
with a distributor's network unless he -

(a) has the necessary and appropriate equipment to prevent danger
or interference with that network or with the supply to consumers so far
as is reasonably practicable;

(b) has the necessary and appropriate personnel and procedures to
prevent danger so far as is reasonably practicable;

(c) where the source of energy is part of a low voltage
consumer's installation, complies with British Standard Requirements; and

(d) agrees specific requirements with the distributor who owns or
operates the network.

(2) Sub-paragraphs (b) and (d) of paragraph (1) shall not apply to
a person who installs or operates a source of energy which may be
connected in parallel with a distributor's network provided that
sub-paragraphs (a) and (c) of paragraph (1) are complied with; and

(a) the source of energy does not produce an electrical output
exceeding 16 amperes per phase at low voltage;

(b) the source of energy is configured to disconnect itself
electrically from the parallel connection when the distributor's
equipment disconnects the supply of electricity to the person's
installation; and

(c) the person installing the source of energy ensures that the
distributor is advised of the intention to use the source of energy in
parallel with the network before, or at the time of, commissioning the
source.
/quote

--
Andy

In article , Andy Wade spambucket@m
axwell.myzen.co.uk scribeth thus
The Wanderer wrote:

cut - does there have to be some mechanisn to prevent back-feeding under
such circumstances?

'Fraid I don't know the answer to that one, but I would imagine so.

Yes, it's a legal requirement in the ESQCR:
quote
Parallel operation
22. - (1) Without prejudice to regulation 21, no person shall
install or operate a source of energy which may be connected in parallel
with a distributor's network unless he -

(a) has the necessary and appropriate equipment to prevent danger
or interference with that network or with the supply to consumers so far
as is reasonably practicable;

(b) has the necessary and appropriate personnel and procedures to
prevent danger so far as is reasonably practicable;

(c) where the source of energy is part of a low voltage
consumer's installation, complies with British Standard Requirements; and

(d) agrees specific requirements with the distributor who owns or
operates the network.

(2) Sub-paragraphs (b) and (d) of paragraph (1) shall not apply to
a person who installs or operates a source of energy which may be
connected in parallel with a distributor's network provided that
sub-paragraphs (a) and (c) of paragraph (1) are complied with; and

(a) the source of energy does not produce an electrical output
exceeding 16 amperes per phase at low voltage;

(b) the source of energy is configured to disconnect itself
electrically from the parallel connection when the distributor's
equipment disconnects the supply of electricity to the person's
installation; and

(c) the person installing the source of energy ensures that the
distributor is advised of the intention to use the source of energy in
parallel with the network before, or at the time of, commissioning the
source.
/quote


All quite "reasonable" and "Practicable"...

Two words which keep me 'learned friends in clover;!..

So how is the actual sensing of the supply failure done?..

Suppose one local 11 kV system fed from one end off the grid..

Other end fed bu local gennie system..

Fault develops in the middle so local gennie tries to supply the load.
Load could be very light middle of the night in summer so no storage
heating etc. Gennie can cope with that..

So apart from the sudden rise of load how can you determine that the
mains network has gone down?...

And I suppose any lines men will obviously see that they earth and short
together the affected line before commencing work;!..
--
Tony Sayer

In article , Jim Michaels
scribeth thus
On 02 Feb 2008 21:48:28 GMT, (Andrew
Gabriel) wrote:

In article ,
tony sayer writes:
I think theres seems to be some confusion here between geniis that
provide standby power in case of mains fail, and that requires a
changeover isolating switch so that gennie cannot be connected to the
mains so as to backfeed it..

The other is where your generation feeds into the mains like say a wind
farm..

Begs an interesting question suppose theres a fault on a HV 11 kV local
network where one of theses is feeding back, or just the one turbine
like that have at the dogs home near Godmanchester how does that -know-
when the local system is down when its feeding into the supply?....

They are required to detect loss of mains supply and immediately
cease generation. I suspect this is done by the part of the circuit
that monitors the mains phase and synchronises the inverter output
with it.

When the installation is "Islanded", it no longer enjoys the frequency
stability of the grid and the inverter (or other part of control
system) senses this lack of stability and cuts the feed to the mains.
This is called "Islanding Protection".

The system would normally continue to supply local loads.
Remove SPAMX from email address

So does the local gennie have an "offset reference" or is it allowed to
run at what speed it will?..

So when it looses its "reference signal" in the load its supplying it
will drift to where exactly?...
--
Tony Sayer

On 3 Feb 2008 12:41:18 GMT, Huge wrote:

Power cuts in rural areas happen more frequently than that.

Indeed, we've had 10 cuts today, ranging from 2 or 3 seconds to 90
minutes.

Complain or at least report it, there is a marginal fault(*) somewhere
that is tripping an auto-recloser. The 2 or 3 second cuts are when it is
tripped and automatically reconnects. Get more than X trips in Y seconds
and it latches open giving the longer cut until someone comes out and
resets it. If it closes without retripping they may or may not decide to
investigate what caused it to latch open.

(*) Anything from a leaky insulator to a bit of tree waving in the wind/
weighed down by ice/snow touching the line. The former won't go away and
will only get worse. The latter might if it's a small bit of tree as the
shorts to earth destroy bits of it.

--
Cheers
Dave.

The message
from Huge contains these words:

On 2008-02-02, Steve Firth wrote:
Appin wrote:

I'm not convinced that it's a very wise basket into which to
put all one's provision for the emergency of a power outage which is
going to occcur, in all probability, once or twice in a decade.

Power cuts in rural areas happen more frequently than that.

Indeed, we've had 10 cuts today, ranging from 2 or 3 seconds to 90
minutes.

)

Half a dozen momentary cuts last weekend.


Granted. And we had seven or eight cuts of several seconds on Saturday
night. Leading to the slightly awkward situation of my commercial
answering machine and voice mailbox provider reprogramming itself to
function entirely in German. Now, I speak German reasonably well, but
...............

It took a bit of effort to find the appropriate menus in German and set
the whole machine up all over again. And yes, this time it's on the UPS
that serves the telephone exchange, wireless router modem etc.

Hardly enough to demand a generator, though, even at 90 minutes, for my use.

Longest cut ever - 4 days.

Haven't had a cut that long in the UK. How many have you had of these
in the last thirty years? :-)

The message
from Jim Michaels contains these words:

When the installation is "Islanded", it no longer enjoys the frequency
stability of the grid and the inverter (or other part of control
system) senses this lack of stability and cuts the feed to the mains.
This is called "Islanding Protection".

Point taken and accepted. And certainly to be present in a gemerating
station as it's locked into the grid by the stable frequency of the grid
is an experience not to be forgotten (think in terms of a very large
bang!). What happens, though, if you've got an extra-stable local
source as some people claim the small Honda generators are? (I KNOW the
grid is stable, I'm not so convinced about any small generator, no
matter how clever they claim to be).

Granted. And we had seven or eight cuts of several seconds on Saturday
night. Leading to the slightly awkward situation of my commercial
answering machine and voice mailbox provider reprogramming itself to
function entirely in German. Now, I speak German reasonably well, but
..............

It took a bit of effort to find the appropriate menus in German and set
the whole machine up all over again. And yes, this time it's on the UPS
that serves the telephone exchange, wireless router modem etc.

Hardly enough to demand a generator, though, even at 90 minutes, for my use.

Longest cut ever - 4 days.

Haven't had a cut that long in the UK. How many have you had of these
in the last thirty years? :-)

On a local comms site five days and for five days the old gennie
struggled a bit;!..

Wasn't till we threatened to repair the cables ourselves that EDF became
interested. In their finest hour...Not!.

End of October 2002 remember it?....
--
Tony Sayer

The message
from tony sayer contains these words:

Granted. And we had seven or eight cuts of several seconds on Saturday
night. Leading to the slightly awkward situation of my commercial
answering machine and voice mailbox provider reprogramming itself to
function entirely in German. Now, I speak German reasonably well, but
..............

It took a bit of effort to find the appropriate menus in German and set
the whole machine up all over again. And yes, this time it's on the UPS
that serves the telephone exchange, wireless router modem etc.

Hardly enough to demand a generator, though, even at 90 minutes, for
my use.

Longest cut ever - 4 days.

Haven't had a cut that long in the UK. How many have you had of these
in the last thirty years? :-)

On a local comms site five days and for five days the old gennie
struggled a bit;!..

Wasn't till we threatened to repair the cables ourselves that EDF became
interested. In their finest hour...Not!.

End of October 2002 remember it?....

Not particularly :-) So that was once in thirty years?

In article , Appin
scribeth thus
The message
from tony sayer contains these words:

Granted. And we had seven or eight cuts of several seconds on Saturday
night. Leading to the slightly awkward situation of my commercial
answering machine and voice mailbox provider reprogramming itself to
function entirely in German. Now, I speak German reasonably well, but
..............

It took a bit of effort to find the appropriate menus in German and set
the whole machine up all over again. And yes, this time it's on the UPS
that serves the telephone exchange, wireless router modem etc.

Hardly enough to demand a generator, though, even at 90 minutes, for
my use.

Longest cut ever - 4 days.

Haven't had a cut that long in the UK. How many have you had of these
in the last thirty years? :-)

On a local comms site five days and for five days the old gennie
struggled a bit;!..

Wasn't till we threatened to repair the cables ourselves that EDF became
interested. In their finest hour...Not!.

End of October 2002 remember it?....

Not particularly :-) So that was once in thirty years?

Well there was quite a wind across East Anglywold that caught the power
company right out..

And there was of course the great storm of 87...

So both in the last 30 years;!...
--
Tony Sayer

The message
from tony sayer contains these words:

In article , Appin
scribeth thus
The message
from tony sayer contains these words:

Granted. And we had seven or eight cuts of several seconds on Saturday
night. Leading to the slightly awkward situation of my commercial
answering machine and voice mailbox provider reprogramming itself to
function entirely in German. Now, I speak German reasonably well, but
..............

It took a bit of effort to find the appropriate menus in German and set
the whole machine up all over again. And yes, this time it's on the UPS
that serves the telephone exchange, wireless router modem etc.

Hardly enough to demand a generator, though, even at 90 minutes, for
my use.

Longest cut ever - 4 days.

Haven't had a cut that long in the UK. How many have you had of these
in the last thirty years? :-)

On a local comms site five days and for five days the old gennie
struggled a bit;!..

Wasn't till we threatened to repair the cables ourselves that EDF became
interested. In their finest hour...Not!.

End of October 2002 remember it?....

Not particularly :-) So that was once in thirty years?

Well there was quite a wind across East Anglywold that caught the power
company right out..

And there was of course the great storm of 87...

So both in the last 30 years;!...

Once in 15 years, then? Not convinced that a massive switch-over system
with a large generator is justified for me even on a once in 15 years
basis, although we haven't had more than two lengthy outages in thirty
years and both were due to poor line maintenance more than anything
else.

I'm not arguing against sensible provision of backup facilities -- it's
more a question of how to go about it in such a way that the provision
is commensurate with the real needs rather than trying to maintain life
unaltered during a power interruption.

In article , Appin
scribeth thus
The message
from tony sayer contains these words:

In article , Appin
scribeth thus
The message
from tony sayer contains these words:

Granted. And we had seven or eight cuts of several seconds on Saturday
night. Leading to the slightly awkward situation of my commercial
answering machine and voice mailbox provider reprogramming itself to
function entirely in German. Now, I speak German reasonably well, but
..............

It took a bit of effort to find the appropriate menus in German and set
the whole machine up all over again. And yes, this time it's on the UPS
that serves the telephone exchange, wireless router modem etc.

Hardly enough to demand a generator, though, even at 90 minutes, for
my use.

Longest cut ever - 4 days.

Haven't had a cut that long in the UK. How many have you had of these
in the last thirty years? :-)

On a local comms site five days and for five days the old gennie
struggled a bit;!..

Wasn't till we threatened to repair the cables ourselves that EDF became
interested. In their finest hour...Not!.

End of October 2002 remember it?....

Not particularly :-) So that was once in thirty years?

Well there was quite a wind across East Anglywold that caught the power
company right out..

And there was of course the great storm of 87...

So both in the last 30 years;!...

Once in 15 years, then? Not convinced that a massive switch-over system
with a large generator is justified for me even on a once in 15 years
basis, although we haven't had more than two lengthy outages in thirty
years and both were due to poor line maintenance more than anything
else.




Well this was for a communications and broadcast site so it is
justified. There have been a lot of other short duration cuts ..


I'm not arguing against sensible provision of backup facilities -- it's
more a question of how to go about it in such a way that the provision
is commensurate with the real needs rather than trying to maintain life
unaltered during a power interruption.

Thats up to how important the supply is to you.. Fine of you like
candlelight but the stuff we maintain isn't steam powered at least not
locally;!..
--
Tony Sayer

On Mon, 4 Feb 2008 21:45:20 +0000, tony sayer wrote:

snip

Well there was quite a wind across East Anglywold that caught the power
company right out..

And there was of course the great storm of 87...

And *that* was supposed to be a 'once in a hundred years' event.


--
the dot wanderer at tesco dot net

In article , The Wanderer
scribeth thus
On Mon, 4 Feb 2008 21:45:20 +0000, tony sayer wrote:

snip

Well there was quite a wind across East Anglywold that caught the power
company right out..

And there was of course the great storm of 87...

And *that* was supposed to be a 'once in a hundred years' event.


Well lets see in another 100 years then...

--
Tony Sayer

The message
from tony sayer contains these words:



Once in 15 years, then? Not convinced that a massive switch-over system
with a large generator is justified for me even on a once in 15 years
basis, although we haven't had more than two lengthy outages in thirty
years and both were due to poor line maintenance more than anything
else.




Well this was for a communications and broadcast site so it is
justified. There have been a lot of other short duration cuts ..

Quite -- but a communications and broadcast site is something of a
special case :-)

Or at least something vastly different from a domestic or SOHO situation.

I'm not arguing against sensible provision of backup facilities -- it's
more a question of how to go about it in such a way that the provision
is commensurate with the real needs rather than trying to maintain life
unaltered during a power interruption.

Thats up to how important the supply is to you.. Fine of you like
candlelight but the stuff we maintain isn't steam powered at least not
locally;!..

But who mentioned candlelight? That would probably be a foolish and
very dangerous option.

I'm simply arguing for

1. An assessment of the risk

2. An assessment of the core needs

3. An assessment of the possible methods of meeting core needs

4. An assessment of the reliability of the various methods of meeting
the core needs

5. An assessment of the maintenance requirements of the various methods
of meeting the core needs

6. An assessment of the true cost of the various methods of meeting the
core needs.


Different situations will come up with very different answers. I have
no up-to-date knowledge of the situation with regard to broadcast sites,
but it seems that transmitter non-availability is much more frequent now
than would have been the case thirty or forty years ago. Is there the
same emphasis on avaialability of backup equipment and generating
capacity as there used to be?

In article , Appin
scribeth thus
The message
from tony sayer contains these words:



Once in 15 years, then? Not convinced that a massive switch-over system
with a large generator is justified for me even on a once in 15 years
basis, although we haven't had more than two lengthy outages in thirty
years and both were due to poor line maintenance more than anything
else.




Well this was for a communications and broadcast site so it is
justified. There have been a lot of other short duration cuts ..

Quite -- but a communications and broadcast site is something of a
special case :-)

Or at least something vastly different from a domestic or SOHO situation.

Indeed..

I'm not arguing against sensible provision of backup facilities -- it's
more a question of how to go about it in such a way that the provision
is commensurate with the real needs rather than trying to maintain life
unaltered during a power interruption.

Thats up to how important the supply is to you.. Fine of you like
candlelight but the stuff we maintain isn't steam powered at least not
locally;!..

But who mentioned candlelight? That would probably be a foolish and
very dangerous option.

Worked fine when I were a lad .. alright houses used to burn down from
time to time..

I'm simply arguing for

1. An assessment of the risk

fine
2. An assessment of the core needs

ditto
3. An assessment of the possible methods of meeting core needs

And again
4. An assessment of the reliability of the various methods of meeting
the core needs

Right isn't that the same as number two..

5. An assessment of the maintenance requirements of the various methods
of meeting the core needs

Don't work for the council or nhs at all?, they go on like this all the
time..


6. An assessment of the true cost of the various methods of meeting the
core needs.


Zzzzzzzzzz.........

Different situations will come up with very different answers. I have
no up-to-date knowledge of the situation with regard to broadcast sites,
but it seems that transmitter non-availability is much more frequent now
than would have been the case thirty or forty years ago. Is there the
same emphasis on avaialability of backup equipment and generating
capacity as there used to be?

Yep right.. Tho a couple of people nearby went a got a lump of 2.5 T&E
and where mighty grateful for a sip of the juice...

--
Tony Sayer