Last night I had a power cut lasting 2 and half hours. This is not
unusual in our village but what was unusual was how it started.
Initially the oven switched off and the kitchen ring went off but all
the lights stayed on albeit dimmer than normal. Over the course of
the next few minutes, various lighting circuits went off and on a few
times before eventually all went off. While all this was happening I
had enough time to check my CU and pop next door to see if they were
affected. We came to the conclusion that a transformer was in the act
of going down but can anyone be more specific?

On Sun, 02 Feb 2014 15:17:41 +0000, Lawrence wrote:

Last night I had a power cut lasting 2 and half hours. This is not
unusual in our village but what was unusual was how it started.
Initially the oven switched off and the kitchen ring went off but all
the lights stayed on albeit dimmer than normal.

What lamps for lighting? CFLs are on or off at more or less the same
brightness over a large supply voltage range. Confused the heck out
of me at 0300 the other winter when an ice storm meant our volts
dropped to not much over 100. CFL lights worked, router, switch,
server where on (SMPSU's), other bits of IT kit not (lump of iron
PSU), tungsten was very red and dim...

Over the course of the next few minutes, various lighting circuits went
off and on a few times before eventually all went off.

Synchronous on/off switching or different circuits at different
times. Synchronous would probably be an auto recloser in the feed
some where detecting a fault, tripping then reconnecting a few
seconds later. If this happens more then n times in x minutes it
locks out in the off state. Saves the DNO having to send an engineer
out to reset after transient faults like lightning or a small branch
touching the line.

--
Cheers
Dave.

On Sun, 02 Feb 2014 15:17:41 +0000, Lawrence
wrote:

Last night I had a power cut lasting 2 and half hours. This is not
unusual in our village but what was unusual was how it started.
Initially the oven switched off and the kitchen ring went off but all
the lights stayed on albeit dimmer than normal. Over the course of
the next few minutes, various lighting circuits went off and on a few
times before eventually all went off. While all this was happening I
had enough time to check my CU and pop next door to see if they were
affected. We came to the conclusion that a transformer was in the act
of going down but can anyone be more specific?


Nothing in that strikes me as unusual for a severe brown-out.

It is normal for an oven to "fail safe" when the power is interrupted
and require you to reset the clock, all that happened was this
occurred during the low voltage period of the brown-out rather than
when it went out completely.

What technology lamps were they? I would expect individual CFLs and
linier florescents to go off at differing voltages.


--
Graham.


%Profound_observation%

On 02/02/2014 16:00, Dave Liquorice wrote:
Saves the DNO having to send an engineer
out to reset after transient faults like lightning or a small branch
touching the line.


Does the small branch cease to exist after the first touch (what a way
to go, in a puff of smoke!), or what stops it touching the line again?

On Sun, 02 Feb 2014 18:07:19 +0000, GB wrote:

Saves the DNO having to send an engineer out to reset after
transient
faults like lightning or a small branch touching the line.

Does the small branch cease to exist after the first touch (what a way
to go, in a puff of smoke!), or what stops it touching the line again?

As you summise a small branch gets exploded. There is a lot of energy
available from an 11kV line, just 100 A fault current @ 11 kV is 1.1
MW of power. A branch doesn't stand a chance...


--
Cheers
Dave.

In article ,
Lawrence writes:
Last night I had a power cut lasting 2 and half hours. This is not
unusual in our village but what was unusual was how it started.
Initially the oven switched off and the kitchen ring went off but all
the lights stayed on albeit dimmer than normal. Over the course of
the next few minutes, various lighting circuits went off and on a few
times before eventually all went off. While all this was happening I
had enough time to check my CU and pop next door to see if they were
affected. We came to the conclusion that a transformer was in the act
of going down but can anyone be more specific?

Do you have a 2- or 3-phase supply?

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

On Sun, 2 Feb 2014 20:46:26 +0000 (UTC),
(Andrew Gabriel) wrote:
In article ,
Lawrence writes:
Last night I had a power cut lasting 2 and half hours. This is
not
unusual in our village but what was unusual was how it started.
Initially the oven switched off and the kitchen ring went off but
all
the lights stayed on albeit dimmer than normal. Over the course
of
the next few minutes, various lighting circuits went off and on a
few
times before eventually all went off. While all this was
happening I
had enough time to check my CU and pop next door to see if they
were
affected. We came to the conclusion that a transformer was in the
act
of going down but can anyone be more specific?


Do you have a 2- or 3-phase supply?


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

Just single phase.

On Sun, 02 Feb 2014 16:00:41 +0000 (GMT), "Dave Liquorice"
wrote:
On Sun, 02 Feb 2014 15:17:41 +0000, Lawrence wrote:


Last night I had a power cut lasting 2 and half hours. This is
not
unusual in our village but what was unusual was how it started.
Initially the oven switched off and the kitchen ring went off but
all
the lights stayed on albeit dimmer than normal.


What lamps for lighting? CFLs are on or off at more or less the same
brightness over a large supply voltage range. Confused the heck out
of me at 0300 the other winter when an ice storm meant our volts
dropped to not much over 100. CFL lights worked, router, switch,
server where on (SMPSU's), other bits of IT kit not (lump of iron
PSU), tungsten was very red and dim...


Over the course of the next few minutes, various lighting
circuits went
off and on a few times before eventually all went off.


Synchronous on/off switching or different circuits at different
times. Synchronous would probably be an auto recloser in the feed
some where detecting a fault, tripping then reconnecting a few
seconds later. If this happens more then n times in x minutes it
locks out in the off state. Saves the DNO having to send an engineer
out to reset after transient faults like lightning or a small branch
touching the line.


--
Cheers
Dave.

Mixture of filament, CFL and linear fluorescent. I guess that answers
my query.

On 03/02/2014 12:17, Lawrence wrote:
On Sun, 02 Feb 2014 16:00:41 +0000 (GMT), "Dave Liquorice"
wrote:
On Sun, 02 Feb 2014 15:17:41 +0000, Lawrence wrote:


Last night I had a power cut lasting 2 and half hours. This is
not
unusual in our village but what was unusual was how it started.
Initially the oven switched off and the kitchen ring went off but
all
the lights stayed on albeit dimmer than normal.


What lamps for lighting? CFLs are on or off at more or less the same
brightness over a large supply voltage range. Confused the heck out
of me at 0300 the other winter when an ice storm meant our volts
dropped to not much over 100. CFL lights worked, router, switch,
server where on (SMPSU's), other bits of IT kit not (lump of iron
PSU), tungsten was very red and dim...

Sounds like the sort of thing that happens when there is an abnormal
load on the line which is insufficient to immediately trip out the
protection circuit but enough to drop the volts at consumer unit.

We used to have a problem like that when the sewage pumping station down
the valley switched on at 6.30pm every night the lights would flicker
and dim until the pump got properly up to speed. NEDL replaced that
cable a while ago and it has never been any bother since.


Over the course of the next few minutes, various lighting
circuits went
off and on a few times before eventually all went off.


Synchronous on/off switching or different circuits at different
times. Synchronous would probably be an auto recloser in the feed
some where detecting a fault, tripping then reconnecting a few
seconds later. If this happens more then n times in x minutes it
locks out in the off state. Saves the DNO having to send an engineer
out to reset after transient faults like lightning or a small branch
touching the line.


Mixture of filament, CFL and linear fluorescent. I guess that answers my
query.

CFL and LED will run OK almost as bright on a surprisingly low mains
voltage but draw more current to do so.

--
Regards,
Martin Brown