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Feeding solar power back into municipal grid: Issues andfinger-pointing

G

g

Jan 1, 1970
0
I'm not arguing that the grid can't or won't take any, the majority, or
all of the generated power.

The question here is - what exactly must the invertors do in order to
get as much current as the PV system can supply into the grid.

The inverter must ensure that it transforms the DC from PV to the
frequency and voltage of the grid. To ensure flow of current into the
grid the voltage must be attempted to be raised. Because there are
losses between the inverter and the grid, the voltage will be higher
than the grid.
If our analogy is pipes, water, and water pressure, then we have some
pipes sitting at 120 PSI and we have a pump that must generate at least
121 PSI in order to push water into the already pressurized pipes.

Fairly good analogy, and due to internal resistance in the pipe then
that must be overcome by having a higher pressure. Don't forget that
somewhere someone else has to reduce the water flow into the pipe system
in order to avoid pressure buildup. Because the water in the pipe system
is used up as it is supplied, at the same rate.

Not sure I understand what you're trying to say there.

See the pipe analogy above, the power lines from the inverter has some
resistance, which results in a voltage drop. Therefore the voltage
measured at the inverter will be slightly higher than measured a
distance away.
No, I don't agree.

Why? take a hypothetical grid with 1 megawatt consumption. Generating
machinery produce that energy at a set voltage. Mr Homeowner connects to
the grid with a 10kW PV array. If no power utility adjustment took place
then the overall voltage of the grid will increase. OK for small
fluctuations, but if enough PV arrays came online, somewhere energy
production has to decrease or bad things will happen due to high grid
voltage.

Hypothetically speaking, let's assume the local grid load is just a
bunch of incandecent lights. A typical residential PV system might be,
say, 5 kw. At 120 volts, that's about 42 amps. How are you going to
push out 42 amps out to the grid?
You cannot unless your local load is zero. You must subtract the local
load from the generated PV array power if the house load is lower. If
the house load is higher than the PV array output then you will use all
the PV array power with the difference supplied from the grid.

They're going to burn a little brighter -
Correct, due to a slightly raised voltage if there is a voltage drop
between the inverter and the grid. (There is some drop)
they're going to use all of the current that the local grid was already
supplying to them, plus they're going to use your current as well.
Not possible, the current is controlled by the internal resistance in
the lamp. They will draw a current by the formula volt/resistance.
So when the PV array produces current, grid current is reduced.

The voltage increase you will see at the output of the inverter is very
small, but it does depend on the cables used.

An example: I have a 300 feet underground cable to the nearest utility
transformer and a 100A service panel.

If I max out the power, I will have a voltage drop over the cable of
about 6 Volts. Much higher than normal households.

When your PV array is producing full power, and your house load matches
that, then the voltage difference between the grid and inverter is zero.

at any other house load, current will flow in the power utility lines,
and the inverter voltage increase is a function of the loss in those
lines.
 
I think you are pushing it....the brushes on a dc motor "guide" the dc
to different windings.....it is still dc...

No, it most definitely is *not*. Turn the motor to the next commutator step
and you'll see that the current reverses in the winding.
In an ac motor the windings are generally in parallel...all the ac is
applied at one time....

I think I got that right....is a long time since I covered motor
theory..<grin>...the ac is not "chopped up"....or guided anywhere....

That's why there are no brushes in AC motors? ;-)
You could say that all electric motors operate the same....as they all
depend on magnetism (all generally used motors...there are some operate
on static electricity, etc)
have fun...sno

....and you need a rotating magnetic field. That is, you need AC. ;-)
 
Wrong. Spindle motors either have brushes and commutators or else the solid
state equivalent. Otherwise, they can't work. Just like the commutators &
brush system, that electronic "stuff" may be built directly into the motor where
you can't see it, but it's still there.

Correct. David should refrain from any EE lectures. He hasn't got it in him.
 
If you do a little research I think you will change your mind.

http://en.wikipedia.org/wiki/Grid_tie_inverter

At the bottom of that page you will find this link

http://www.solarpanelsplus.com/solar-inverters/How-Solar-Inverters-Work-With-Solar-Panels.pdf


More specificly I wrote, "forcing power back into the grid". Power is
watts or KW. That's volts times amps.

But watts is *not* volts times amps, in an AC circuit. There is a power
factor in there to worry about. In the capacitor example, watts dissipated is
zero (or close to it) but VA might be rather high.
The current will only flow if there is a difference in voltage.

Correct. Ohms Law.
 
D

David Nebenzahl

Jan 1, 1970
0
Correct. Ohms Law.

That is *not* Ohm's Law. Where do you get that? Sheesh--you're trying to
lecture *me* on this stuff???


--
The current state of literacy in our advanced civilization:

yo
wassup
nuttin
wan2 hang
k
where
here
k
l8tr
by

- from Usenet (what's *that*?)
 
B

bud--

Jan 1, 1970
0
in message


This is a fatal flaw in your argument. Transformers are not infinite
sources. A utility transformer might supply a fault current 20x the
rated current (for a "5% impedance" transformer). (While a transformer
will supply a fault current larger than the rated current that is not
likely with PV. PV is basically a constant current source.)


Using a real transformer houses will have far less available fault current.


Cite where 100kA is required.


I agree that is very likely. One reason is that a higher rating is not
necessary.

(SquareD, if I remember right, has a rating of 20kA downstream from both
the main and branch circuit breaker.)

I doubt many Canadian house panels have fuse protection, or are
different from US panels with circuit breaker protection rated around 10kA.


The interrupt rating required goes up with the service current rating.
For a house, the utility is not likely to have over 10,000kA available
fault current. The transformers become too large, many houses are
supplied with longer wires and higher resistance losses, and the system
is much less safe.

I believe it would take a rather massive amount of PV installations to
cause a problem. The PV installations would all have to be on the
secondary of the same utility transformer. The transformer is then not
likely to support the PV current back to the grid. If the fault current
is 20x the transformer full load current, and the PV current is equal to
the transformer full load current, the PV supply would increase the
fault current by about 5% (assuming the inverter doesn't shut down). If
there were too many PV installations the utility could put fewer houses
on a transformer. Seems like a problem that is not that hard to handle
for the utility, at least until PV generation becomes rather common.
*--
bud--

-----------------
|Perhaps re-read ( or just read ) the last few posts. Your objection is
|mostly agreement with items already covered.

Perhaps you should take reading lessons. Maybe you and harry could get
group rates.

- You said "considering the street transformer as an infinite current
supply" which no one does.
- As a result your calculation is meaningless.
- You said Canadian house panels were protected with fuses. I disagree.
Perhaps a cite?
- You said "any approved O/C device in a panel these days is rated at
100kA". I asked for a cite - still missing.

- Daestrom said adding PV systems to residences could result in an
available fault current larger than the rating of existing service
panels. It is certainly an interesting point, but not likely for reasons
stated.

I did agree with daestrom that most US house panels are likely to have a
10kA IR.


|Can you cite the percent impedance of the transformers

5% impedance would be common

| or the code rules you discuss?

I didn't discuss code rules.


Your 'newsreader' is incompetent at treating sigs.
 
B

bud--

Jan 1, 1970
0
In theory transformers can carry any load.

If you are talking about normal load ratings - what a useful revelation.
I am sure no one had any idea...
In practice there are losses due to resistance of the copper wire and
in the iron core that cause heating. How swiftly this heat can be
dissipated is one load carrying limtation. How much heat the
insulation can stand is another.

There is a limit on the normal current for a transformer?
I had no idea....

But heating is not a limit on fault current (which my post was almost
entirely about).
Fault currents are determined by assessing the "loop" resistance of a
worst case electrical fault to earth and also as a dead short. These
can be determined by calculation or by instruments.

Earth is not calculated because it is such a poor conductor. It may be
necessary in some of the screwier UK electrical systems with an RCD main.
So any switch or circuit breaker has two current ratings.

It's normal rating that it will carry continuously and interrupt many
thousands of times.

It's fault current rupturing capacity. Often several thousand amps. It
will only break this current a very limited number of times and carry
the current for milliseconds.

With minimal reading ability it is obvious that daestrom, mII (or
whoever) and I talked about the fault current ratings of circuit
breakers or fuses. Or did you think that houses have 10,000A services?
You really need to go for some instruction. These things can't be
worked out by lying on your bed and thinking about it.

I worked them out 40 years ago then worked with them the last 40 years.

You really should learn to read and think. Maybe when cows fly....
 
H

Home Guy

Jan 1, 1970
0
harry said:
What happens to the "say" 1 volt. It is only a local thing because
the utility drops it's output by 5Kw.

I doubt that the regional sub-station is going to do that.
Sure, there will be different current flow around the system
but nothing that can't be handled.

I didn't say that it couldn't be handled.

I'm saying that a small-scale PV system is going to raise the local grid
voltage for the homes connected to the same step-down distribution
transformer. All the linear loads on the local grid will consume the
extra power (probably about 250 to 500 watts per home, including the
house with the PV system on the roof). The extra 250 to 500 watts will
be divided up between the various AC motors (AC and fridge compressors,
vent fans) and lights. They don't need the extra volt or two rise on
their power line supply - the motors won't turn any faster and the
lights will just convert those extra watts into heat more than light
output.

The home owner with the PV system will get paid 80 cents / kwh for the
40-odd amps he's pushing out into the grid, but that energy will be
wasted as it's converted disproportionately into heat - not useful work
- by the linear loads on the local grid.
I don't know why you rabbit claiming it doesn't work when it
clearly does.

I don't see a rabbit around here.

I'm not claiming that pushing current into the local grid by way of
raising the local grid voltage doesn't work.

I'm claiming that there won't be a corresponding voltage down-regulation
at the level of the neighborhood distribution transformer to make the
effort worth while for all stake holders.
 
That is *not* Ohm's Law. Where do you get that? Sheesh--you're trying to
lecture *me* on this stuff???

E=IR, certainly *IS* Ohm's law. I and E are proportional. You can't increase
I without increasing E. Get it? I suppose not.
 
V

vaughn

Jan 1, 1970
0
E=IR, certainly *IS* Ohm's law. I and E are proportional. You can't increase
I without increasing E.
Wrong. You CAN increase I without increasing E. You have 3 variables in that
formula, not just 2.

Get it? I suppose not.

Apparently not.

Vaughn
 
G

g

Jan 1, 1970
0
harry wrote:


I doubt that the regional sub-station is going to do that.

From Wikipedia:
"In an electric power distribution system, voltage regulators may be
installed at a substation or along distribution lines so that all
customers receive steady voltage independent of how much power is drawn
from the line."

Obviously when a local area is supplying power to the grid, power
generation elsewhere will be reduced. And any voltage changes that
results from that will be adjusted with line voltage regulators, if
necessary.


I'm saying that a small-scale PV system is going to raise the local grid
voltage for the homes connected to the same step-down distribution
transformer.All the linear loads on the local grid will consume the
extra power (probably about 250 to 500 watts per home, including the
house with the PV system on the roof). The extra 250 to 500 watts will
be divided up between the various AC motors (AC and fridge compressors,
vent fans) and lights. They don't need the extra volt or two rise on
their power line supply - the motors won't turn any faster and the
lights will just convert those extra watts into heat more than light
output.

How do you get the value 250-500W?

Motors will only increase their energy drain by raising the frequency,
Plus a small loss due to internal resistance in the windings.

As for a resistive load, increasing the voltage from 120 to 125 volt
will result in a power drain increase of about 8.5% or 8.5 W for a 100W
light bulb, assuming 120V is the nominal voltage.

Remember though that the voltage increase on the step-down side of the
transformer due to homeowners PV arrays will be less than 5 volt pretty
much guaranteed. Local codes state a maximum voltage drop (7V in BC)
over the lines to a house, at 80% load of service panel capacity.

Most households have a 200A service panel. A 10kW PV array is well below
the service panel capacity.

And you cannot just look at the PV array output. You must take into
account the local energy consumers as well. That will reduce the current
going into the grid, and thus the voltage increase.
The home owner with the PV system will get paid 80 cents / kwh for the
40-odd amps he's pushing out into the grid, but that energy will be
wasted as it's converted disproportionately into heat - not useful work
- by the linear loads on the local grid.

You claims are pretty vague, please explain what you mean by wasted.

By the way, there is some "waste" by just using the grid only as well.
Losses everywhere in the grid.
I'm claiming that there won't be a corresponding voltage down-regulation
at the level of the neighborhood distribution transformer to make the
effort worth while for all stake holders.

What is your definition of worth while? And what do you know about the
utility's voltage regulation policies?

The utilities _have_ to use voltage regulation due to demand changes.
 
D

Daniel who wants to know

Jan 1, 1970
0
Home Guy said:
I'm claiming that there won't be a corresponding voltage down-regulation
at the level of the neighborhood distribution transformer to make the
effort worth while for all stake holders.

Oh but there is. Look around and you will see an occasional unit that looks
like a pole pig (transformer) with no low voltage wires attached, just the
high voltage ones. This is either a line reactor of some kind (inductor or
capacitor) or an on-load tap changer, which is an autotransformer that
automatically changes winding taps as needed to maintain the output voltage
within the 5 or 10% of spec.

If the load on it is say 50KVA and you switch on a GTI with a perfect 1.0
power factor and outputting 25KW the load on that transformer will drop to
25KVA, since all wiring has some resistance this will cause the voltage to
rise the same as if half of the load were switched off, the tap changer
responds after a delay period by changing taps which lowers the output
voltage back down.
 
M

m II

Jan 1, 1970
0
"m II" wrote in message
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On 11-04-11 07:45 PM, m II wrote:

nothing



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My apologies to any of my readers left.

Please read the headers and note I have never used the NNTP x-privat.org
and I have never used any encoding methods. That would be very inconsiderate
to my readers.

Any usage of another NNTP constitutes forgery and has been reported many
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Specifically -- [email protected]



mike
 
V

vaughn

Jan 1, 1970
0

Names? Didn't your mother tell you how babyish that is?
, it's a fixed circuit.

You never defined the circuit, except perhaps in your own mind. I was
responding to your statement about E=IR.
You've only proved that you're just as stupid as David.

And you have proven yourself as a troll.

Bye
Vaughn
 
H

Home Guy

Jan 1, 1970
0
EFFECTS OF PHOTOVOLTAICS ON DISTRIBUTION SYSTEM VOLTAGE REGULATION

Peter McNute, Josh Hambrick, and Mike Keesee

National Renewable Energy Laboratory, Golden, Colorado
Sacramento Municipal Utility District, Sacramento, California

ABSTRACT

As grid-integrated photovoltaic (PV) systems become more prevalent,
utilities want to determine if, and at what point, PV systems might
begin to negatively impact the voltage regulation of their distribution
systems. This paper will briefly describe voltage regulation methods in
a utility distribution system. It will also take a preliminary look at
the distribution impacts of high penetrations of grid-integrated PV
systems being installed and operated in a Sacramento Municipal Utility
District community. In particular, the issue of excessive service
voltage and excessive substation voltage due to the reverse power flow
from exporting PV systems will be examined. We will also compare
measured data against modeled data.

Index Terms - Photovoltaic (PV), Distribution System, Voltage Regulation

INTRODUCTION

A three-year, joint project between the National Renewable Energy
Laboratory (NREL) and Sacramento Municipal Utility District (SMUD) began
in March 2008 to analyze the distribution impacts of high penetrations
of grid-integrated renewable energy systems, specifically PV-equipped
SolarSmartSM Homes found in the Anatolia III Residential Community
(hereafter referred to as Anatolia) in Rancho Cordova, California.
SolarSmart Homes combine high-efficiency features along with
rooftop-integrated 2.0-kWac PV systems with no energy storage. When
completely built out, Anatolia will have 795 homes, 600 of which will be
SolarSmart, eventually amounting to 1.2 MWac potential generation. (So
far, only 115 homes have been built for 238 kWac potential generation.)
In particular we are investigating if there will be excessive service
voltage or substation voltage due to reverse power flow from exporting
PV systems.

VOLTAGE REGULATION METHODS

The primary distribution voltage needs to remain within ANSI C84.1
limits: 114 V to 126 V or 11.4 kV to 12.6 kV, over the length of the
feeder. The service voltage is provided to the customer meter and
includes any voltage drop from the primary service through the
distribution transformer and service conductors. The electric supply
system is designed so that the voltage is within the 110 V to 126 V
range (Range A) most of the time and infrequently within the 106 V to
127 V range (Range B). The utilization voltage is the operating voltage
system and loads are designed to operate within. During heavy loading,
SMUD may adjust the substation voltage as high as 12.75 kV to account
for the voltage drop at the end of the feeder.

Load Tap Changer

A load tap changer (LTC) effectively varies the transformer turns ratio
to maintain the transformer secondary voltage at the substation as
primary-voltage changes occur due to changes in loading of the
transmission system, or as the load on the transformer itself varies.
The Anatolia substation voltage is automatically controlled by a LTC on
the secondary of the substation transformer, managed by a voltage
regulating relay. The band center is 123 V (12.3 kV lineto- line at the
substation). The bandwidth is +/- 1.5 V (or 3.0 V) total. The time delay
for adjustments is 60 seconds. The LTC compensates for added load by
increasing the band center linearly from 123 volts at no load to 126
volts at full load (about 20 MVA or 1,200 A).

Capacitors

Capacitors are reactive power sources that affect the voltage by
supplying leading reactive current that compensates for the lagging
reactive current of the load. The Anatolia substation has six
three-phase, 1,800kVAR capacitor banks (hereafter referred to as
capacitors). The capacitors are computer controlled using an algorithm
developed by SMUD called Capcon. During normal operations, one capacitor
is turned on each time the VAR flow exceeds 900 kVAR (from the
substation bank), and a capacitor is switched off each time the VAR flow
exceeds -1,200 kVAR. These set points are modified on days hotter than
100oF, but this setting can be manually overridden depending upon
weather forecasts. These settings automatically adjust for abnormally
high or low bulk system voltages.

SMUD ANATOLIA III OVERVIEW

Distribution System Description

Anatolia is a residential community served by individual single-phase
lateral circuits from a three-phase primary feeder which connects to a
20 MVA, 69 kV/12.47 kV delta-wye transformer at the Anatolia-Chrysanthy
Substation (hereafter referred to as Anatolia-Chrysanthy or substation).
The feeder has several points along the line that allow for switching.
The length of the feeder to the switching cubicle furthest from the
substation is about 18,895 feet and the furthest distribution
transformer, 5K7, is about 22,360 feet from the substation. In Anatolia,
there are a total of 85 singlephase pad-mounted distribution
transformers: 23 are 75 kVA and 62 are 50 kVA. Also connected to the
same substation feeder is a rendering plant fed by two 1,500kVA
transformers, consuming between 20 and 200 kW, a water storage plant,
and a residential community with an estimated 1,000 homes between the
substation and Anatolia. There are two additional feeders that also
connect to the 20-MVA transformer that have an additional estimated
1,000 customer loads each.

SolarSmart Homes Description

SolarSmart Homes are advertised as able to reduce annual residential
electric bills by 60%. They combine cost-effective, energy-efficient
features and a rooftop PV system. Typical SolarSmart Home features
include: radiant barriers to reflect summer heat that would otherwise
enter the attic and cause greater need for air conditioning;
90%-efficient furnaces; 14 SEER / 12 EER HVAC systems;
compact-fluorescent lighting; ENERGY STAR-qualified windows; and
independent third-party verification, required to confirm all
energy-efficiency measures are installed and operate correctly.

A 2.0-kWac PV system can generate a major portion of the electrical
energy consumed in the home. The majority of the Anatolia PV systems
comprise 36 SunPower 63-watt SunTile roof-integrated modules feeding
into a SunPower SPR-2800x positive-ground, grid-connected inverter. The
inverter can be remotely accessed by SunPower if the homeowner elects to
connect it via the internet. The orientation of the PV systems ranges
from southeast to southwest.

MONITORING

The distribution system is monitored at the substation feeder using a
DAQ Electronics ART-073-79-0 Supervisory Control and Data Acquisition
(SCADA). The SCADA is ANSI-class high-accuracy, better than 0.5%. The
sampling rate is every two seconds with an average recorded every five
minutes. Four distribution transformers are monitored using PMI Eagle
440 monitors having an accuracy better than 1.0%. The sampling rate is
256 samples per cycle with an average recorded every five minutes. Four
homes are monitored at the service panel using PMI iVS-2SX+ power
monitors having an accuracy better than 1.0%. The sampling rate is 128
samples per cycle with an average recorded every five minutes.

Solar and metrological data are also collected from a
solar/meteorological station installed at the substation.
One-minute-interval data from the solar/meteorological station are
collected automatically daily.

ANATOLIA RESULTS

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. The voltage amplitude
was 124.5 V at its peak, so it remained well within ANSI C84.1 limits.
Due to heavy home loads in the morning, the PV system did not begin to
export to the distribution system until almost noon. In March 2009,
there was a 2.0-kWac PV system on the home, 30.1 kWac of PV on the
transformer (twelve SolarSmart Homes), and 238 kWac of PV on the
distribution system (115 SolarSmart Homes). Preliminary estimates of PV
penetration levels on the feeder were 11% to 13% under lightly-loaded
conditions (2.0 MW) and around 4.0% of the total substation transformer
load. Since the PV penetration levels are still relatively low, there
were no adverse effects on voltage regulation.

Modelling Anatolia

To measure the effects of PV on voltage regulation, a Distributed
Engineering Workstation (DEW) model was created that included the
distribution transformers, secondary, and service connections. Once
validated using measured field data, the model will be used to determine
acceptable levels of PV penetration.

The feeder contains significant loads which are not part of the system
under evaluation including a rendering plant, water storage facility and
approximately 1,000 residential customers. Additionally, the substation
transformer and LTC are shared by two unmonitored feeders.

For initial testing and model verification, the unknown residential
loads were represented as a lumped spot load. Eventually, the
residential loads will either be calculated from load research
statistics or distributed based on distribution transformer size. The
rendering plant load was represented as a spot load based on recorded
data.

The load on the other feeders was modeled using a spot load placed
immediately after the LTC. Since the additional feeders share the LTC,
the load on those feeders will affect the position of the tap as well as
the regulation set-point. While the load on the other feeders will not
greatly affect the voltage profile of the system under study, these
loads may affect the voltage regulation.

To verify the topology of the model and to ensure the switching devices
are represented in their correct states, the electrical distances from
the substation of the measurement points were compared against the
values estimated from a GIS map. Table 1 describes this comparison. All
modeled electrical distances are within 3.5% of the estimated distances
as determined from GIS drawings.

Next, the behavior of the secondary-side of the distribution transformer
was validated against real data. The voltage rise measured between the
secondary of the distribution transformers and the service entry to the
homes will be affected by the loads and generation of the other,
unmonitored homes that share the secondary connection.

Figure 2 shows the simulated and measured voltage rise from Home 3 to
the secondary of Transformer 3 (8K6). The data reflects roughly a month
of data where Home 3 is net exporting real power with an inductive load
between 0.18 kVAR and 0.22 kVAR. The secondary system was simulated
assuming uniform generation from all customers connected to the
secondary of the transformer. The generation from the homes was
increased while maintaining a constant inductive load of 0.2 kVAR. The
homes were modeled as constant current loads.

The variation in measured voltage rise data is largely due to
uncertainties with the other customers sharing the secondary connection
as well as the resolution of the voltage measurement device at the home.
Figure 2 indicates that the model reasonably reflects the behavior of
the actual system. With improved monitoring and meter accuracy, the
model could be better validated and, if necessary, adjusted to more
accurately reflect the system.

Currently, there are too many uncertainties on the circuit to perform
any meaningful whole system validation. Efforts are under way to
increase the monitoring on the system so that the overall model may be
better validated. This includes adding meters at critical points to
eliminate many of the unknown loads described above.

CONCLUSIONS

After one year of monitoring the Anatolia SolarSmart Homes Community,
there was no excessive service or substation voltage due to reverse
power flow from exporting PV systems. Preliminary estimates of PV
penetration levels on the feeder were 11% to 13% under lightly-loaded
conditions (2.0 MW) and around 4.0% of the total substation transformer
load. 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. This slight voltage rise was approximately
0.6% on clear days in comparison to the normal drop of -0.6% without the
PV exporting. The DEW model that has been developed reasonably reflects
the behavior of the actual system. The model will be used to determine
acceptable levels of PV penetration.

================

Photovoltaic Specialists Conference (PVSC)
2009 34th IEEE
Issue Date: 7-12 June 2009
On page(s): 001914 - 001917
Date of Current Version: 17 February 2010
 
Names? Didn't your mother tell you how babyish that is?

She taught me to tell the truth. I did.
You never defined the circuit, except perhaps in your own mind. I was
responding to your statement about E=IR.

You're illiterate, then. Not surprising either.
And you have proven yourself as a troll.

No, you insist on demonstrating just how stupid you really are, though.
 
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