Posted by daestrom on April 19, 2011, 8:56 pm
On 4/18/2011 12:05 PM, Mho wrote:
> Why would there be a local increase in the voltage?
> The grid is filled with tapchangers and capacitors to adjust the voltage
> to a constant level, loads on a complex grid can shift load continuously
> to another place. A small PV source may increase the voltage up to the
> next house and would never be noticed.
Like he said, if there is a change in the current flow there is a change
in the voltage drop across each component between you and 'the grid'.
The impedance of these components is small, but nevertheless it exists.
Besides, grid voltage regulation is not perfect. Those tap-changers you
mentioned have discrete steps and most have time-delays in them with a
dead-band around their set-point. These are designed so the thing
doesn't wear out constantly stepping up and down when the voltage
set-point is 'between' the tap settings.
daestrom
<snip>
Posted by Jim Wilkins on April 19, 2011, 9:28 pm
> ...Those tap-changers you
> mentioned have discrete steps and most have time-delays in them with a
> dead-band around their set-point. These are designed so the thing
> doesn't wear out constantly stepping up and down when the voltage
> set-point is 'between' the tap settings.
> daestrom
> <snip>
Would the contacts be the tungsten (heavy) cylindrical slugs sometimes
found below equipment-laden power poles?
jsw
Posted by no spam on April 20, 2011, 9:53 am
>> ...Those tap-changers you
>> mentioned have discrete steps and most have time-delays in them with a
>> dead-band around their set-point. These are designed so the thing
>> doesn't wear out constantly stepping up and down when the voltage
>> set-point is 'between' the tap settings.
>>
>> daestrom
>> <snip>
>Would the contacts be the tungsten (heavy) cylindrical slugs sometimes
>found below equipment-laden power poles?
>jsw
.. twould be a strange grid/retic system indeed were
tap change contacts found in the environment.
Then again I am not surprised at anything uttered
from those who feed the Gymmy Bob troll.
GB will be very busy searching his digests of
"Popular Mechanics" for the term "dead-band"
just to be sure it isn't an old Bob Marley joke:->
.. mind how you go. Don't want you
bleeding all over the place:-D
Posted by daestrom on April 22, 2011, 11:14 pm
On 4/19/2011 17:28 PM, Jim Wilkins wrote:
>> ...Those tap-changers you
>> mentioned have discrete steps and most have time-delays in them with a
>> dead-band around their set-point. These are designed so the thing
>> doesn't wear out constantly stepping up and down when the voltage
>> set-point is 'between' the tap settings.
>>
>> daestrom
>> <snip>
> Would the contacts be the tungsten (heavy) cylindrical slugs sometimes
> found below equipment-laden power poles?
> jsw
The few tap-changers I've seen 'up close and personnel' are in
sub-stations, not pole-mounted. The contacts are in oil-bath and
arranged such that they don't open under appreciable current (multiple
contacts, a center-tapped inductor and ingenious mechanism).
daestrom
Posted by Mho on April 23, 2011, 3:48 am
Similar experiences here.The contacts are usually just copper or copper
plated with silver.
Many schemes are contrived to save the wear and tear on the contacts. On
larger capacity units there are two sets of contacts, ones that take the arc
and are easy to replace and a second set that can carry big currents, close
last and open first.
Some use vacuum bottled contacts to eliminate arcing and most use an
inductor or resistance not as good) to afford tap changing without ever
breaking the circuit.
Oh, I have dealt with a few pole mounted units for inline use in the rural
long lines to boost it back up a bit.
--------------
The few tap-changers I've seen 'up close and personnel' are in
sub-stations, not pole-mounted. The contacts are in oil-bath and
arranged such that they don't open under appreciable current (multiple
contacts, a center-tapped inductor and ingenious mechanism).
--------------
On 4/19/2011 17:28 PM, Jim Wilkins wrote:
Would the contacts be the tungsten (heavy) cylindrical slugs sometimes
found below equipment-laden power poles?
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> The grid is filled with tapchangers and capacitors to adjust the voltage
> to a constant level, loads on a complex grid can shift load continuously
> to another place. A small PV source may increase the voltage up to the
> next house and would never be noticed.