On Apr 15, 9:14*am, Home Guy wrote:
" wrote:
But clearly he thinks if we put a second AC power source on
a distributions system, it has to be at a higher voltage to
"push" current out.

The IEEE paper I posted earlier today shows exactly that - that PV
systems raise local grid voltage and the utility company must
compensate by reducing primary supply voltage to down-regulate the
secondary voltage coming from the distribution transformer.

What a dumbass!

You're the dumbass! *

Read the following:

=============
SMUD wanted to investigate what effect reverse power flow from exporting
PV systems would have on service and substation voltage regulation.
Figure 1 shows the Home-to-Substation voltage difference (top) and solar
irradiance (bottom) on a clear, cool day, Saturday, March 7, 2009,
representative of a day with relatively low load and high local PV
penetration. Penetration is defined as the amount of PV output divided
by the load at a particular point in time.

At night the substation voltage ranged between 0.4 V to 0.7 V higher
than the home voltage. This is representative of a typical circuit with
voltage drops through the line and transformer impedances. During
daylight hours, this reversed and the home voltage rose as high as 0.7
V, or 0.6%, greater than the substation voltage.
============

Did you read the last sentence dumbass?

The differential between substation and home voltage went from -.7 to
+.7 volts - a difference of almost 1.5 volts *due to the effect of the
PV panels injecting current into the grid.

If, according to you, there was no such phenomena of an increase in
local grid voltage caused by PV panels, then there should be no basis
for the point of this IEEE research paper I posted yesterday.

But engineers know that there will be a voltage increase because of
these panels, and the excercise now is to figure out how much PV power
can come on-line before the substation becomes unable to properly
regulate it's output voltage levels.

==============
Since the PV penetration levels were relatively low, there were no
adverse effects on voltage regulation. It was possible to see the
effects of the PV systems on the voltage at the individual homes and the
distribution transformers.
==============

There will be more PV-equipped homes coming on-line in that project and
it's not yet known if in total their operation will cause poorly
controlled or unstable grid voltage.

Take a 12 V car battery and wire it up in parallel with 8 AAA
batteries connected in series. *Then connect a load and tell me
how much current the AAA batteries will supply vs their what
their potential current supply could be if they were connected
to their own isolated load.

They will share in proportion to their capacity.

Capacity is the "quantity of electrons" - which by itself tells you
nothing of the potential (voltage).

Electricity, water, nor **** flow uphill.

And height is exactly equivalent to voltage potential.

So PV panels can't push current into the grid unless the invertors raise
their voltage higher than the grid voltage. *Just matching the grid
voltage gets you to the point where your current flow is ZERO.

Total nonsense and such a basic failure at elementary circuit basics
that it discredits just about anything else you have to say. The
voltage
of the array IS the voltage of the grid at the point it's connected.
How
can it be anything else, unless you want to include the resistance of
the wire used to make the connection, which is immaterial for the
discussion.



*Every
millivolt you adjust your output voltage higher than the grid voltage
means some small increment in current outflow from your panels. *Since
you can't store the energy coming from the panels via battery bank, then
it's in your best interest to always maximize the amount of current
you're injecting into the grid up to the full potential of the panel's
output capacity. *That means raising the output voltage as high as you
need to so that every milliamp is squeezed out of them and onto the
grid.

Take a look at the dual voltage source circuit diagram that Jim
Wilkins
supplied a couple posts back. It's example #1.

http://www.electronics-tutorials.ws/...its/dcp_4.html

It's a simple diagram of two ideal voltage
sources with series resistors connected to a load. That serves as a
basic model for two batteries or two generators or two PV arrays, etc
connected to a load. The example gives the full equations for what
would be two batteries of differing voltages and internal resistance
connected in parallel to a load. Change the voltages so that they
are equal, make them 20V. Solve those equations and you'll find
that BOTH sources are supplying current to the load. The
voltage on the "grid", ie across the load resistor is just one value.
One source is not at a higher value to "push" current.

And I'll bet if you do the equations with the voltage sources at the
same value, you'll find that twice as much current flows from the
voltage source with the 10 ohm resistor as the one with the 20
ohm resistor.