NREL is a national laboratory of the U.S. Department of Energy, Office of Energy 

Efficiency & Renewable Energy, operated by the Alliance for Sustainable Energy, LLC.

Contract No. DE-AC36-08GO28308

Maximum Photovoltaic 

Penetration Levels on Typical 

Distribution Feeders

Preprint

Anderson Hoke, Rebecca Butler, 

Joshua Hambrick, and Benjamin Kroposki

To be published in IEEE Transactions on Sustainable Energy

Journal Article

NREL/JA-5500-55094

July 2012
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1 

Maximum Photovoltaic Penetration Levels on Typical Distribution Feeders

Anderson Hoke, Rebecca Butler, Joshua Hambrick, and Benjamin Kroposki

Abstract

This paper presents simulation results for a taxonomy of typical distribution feeders with various levels 

of photovoltaic (PV) penetration. For each of the 16 feeders simulated, the maximum PV penetration 

that did not result in steady-state voltage or current violation is presented for several PV location 

scenarios: clustered near the feeder source, clustered near the midpoint of the feeder, clustered near 

the end of the feeder, randomly located, and evenly distributed. In addition, the maximum level of PV is 

presented for single, large PV systems at each location. Maximum PV penetration was determined by 

requiring that feeder voltages stay within ANSI Range A and that feeder currents stay within the ranges 

determined by overcurrent protection devices. Simulations were run in GridLAB-D using hourly time 

steps over a year with randomized load profiles based on utility data and typical meteorological year 

weather data. For 86% of the cases simulated, maximum PV penetration was at least 30% of peak load.

Keywords

Distributed power generation, photovoltaic systems, power distribution, power system simulation

I. Introduction

As the portion of electrical energy produced by distributed resources increases, concerns heighten over

the potential for such resources to create steady-state voltage or current violations on electrical 

distribution feeders [1 ]-[3]. When power generated from distributed resources exceeds the load on a 

feeder or section of a feeder, voltages may rise on that section. In addition, significant aggregations of 

distributed resources may cause feeder currents to approach or exceed design currents. This study 

simulates various levels of photovoltaic (PV) penetration on several typical distribution feeders at a 

variety of locations on the feeders, in order to determine which levels of penetration create voltage or 

current problems. This work considers only steady-state voltage and current. It does not consider 

generation ramp rates, protection and coordination, or other issues that might impact maximum feeder 

PV penetration. Some of the maximum PV penetration results presented here are very high and are best 

interpreted as indicating that steady-state voltage and current do not limit PV penetration in the 

relevant cases, not that very high PV penetrations are necessarily achievable.

A commonly used rule of thumb in the U.S. allows distributed PV systems with peak powers up to 15% 

of the peak load on a feeder (or section thereof) to be permitted without a detailed impact study [4]. 

This necessarily conservative rule has been a useful way to allow many distributed PV systems to be 

installed without costly and time-consuming distribution system impact studies. However, as total 

distributed PV power increases on many feeders, and as PV systems whose peak power is a significant 

fraction of feeder capacity become more common, a more rigorous study of the impacts of various PV 

penetration levels on feeder voltages and currents is justified.
2 

To model the effects of various PV penetrations across the wide spectrum of U.S. distribution feeder 

architectures, this study employs a publicly available taxonomy of 24 radial distribution feeder models 

developed at Pacific Northwest National Laboratory (PNNL) [5]. The 24 models represent detailed utility 

feeder models, which statistically represent typical radial distribution feeders from five U.S. climate 

regions. The models are based on 575 utility feeder models gathered from 17 utilities including public, 

municipal, and investor-owned utilities, as well as Rural Electrification Association members. The 

taxonomy feeders do not contain geospatial information, as a condition of the agreement under which 

the utilities provided the models. The simulation platform used to model the feeders is PNNL’s GridLABD version 2.2 [6]. Due to software limitations, eight of the 24 feeders were not used in this study.

For this study, each of the load points in the 16 taxonomy feeders was populated with hourly averaged 

load data from a utility in the feeder's geographical region [5], scaled and randomized to emulate real 

load profiles. Photovoltaic systems driven by typical meteorological year (TMY2) weather data were 

then inserted in each feeder model according to each of the location scenarios described in Section II. 

For each combination of feeder and PV location scenario, annual simulations were performed at PV 

penetration levels of 15% of peak load, 30% of peak load, 45% of peak load, etc. Maximum and 

minimum feeder voltages were recorded for each simulation, and simulations were continued at 

increasing PV levels until voltage exceeded ANSI Range A or current exceeded the overcurrent 

protection rating at some point in the circuit. In this manner, maximum PV penetrations were 

determined for each feeder under each PV location scenario. This process is described in detail in 

Section II, and results are presented in Sections III and IV. 

II. Methodology

In this study, PV penetration is defined as the ratio of total peak PV power to peak load apparent power 

on the feeder:

PV Penetration = (Peak PV Power) / (Peak Load Apparent Power)

A. Feeder Loading 

The taxonomy feeders used for this study do not incorporate time-varying load information. Annual load 

profiles (8760 hourly loads) were developed for each load location using three steps:

1. An appropriate averaged load profile for each load class (commercial and residential) was 

obtained from a utility in the feeder's geographical region, as defined in [5]. For region 5, 

comprising the far Southeast near the Gulf of Mexico, no load profile information was publicly 

available, so load profile data from region 4 was used. Commercial loads were assigned a load 

profile from the utility's medium- or large-sized commercial/industrial load class, and residential 

loads were assigned a load profile from the residential load class.

2. The load profiles were then scaled according to a feeder-specific scale factor, sf, and the 

transformer capacity at each load point. In this study, sf is defined as the ratio of peak apparent 

load power to total rated load transformer apparent power. For each feeder, sf was determined 

by running multiple yearly simulations with one-hour time steps, varying sf. A bisection search 

was used to find the maximum sf for each feeder that maintained load voltages within ANSI 
3 

Range A, line currents below their respective continuous current ratings, and fuse currents 

below fuse ratings. Fig. 1 shows the maximum scaled load found by simulation for each feeder 

alongside its nominal load given in [5]. Fig. 2 shows an analysis of the correlation between 

maximum scaled feeder loads as found by simulation and nominal feeder loads. While overall 

correlation between simulated maximum load and nominal load is relatively strong, certain 

individual feeder peak loads diverge significantly from nominal loads because the same loading 

algorithm was applied to all feeders. This has a significant impact on PV penetration results and 

contributes to some anomalous results discussed later; for example, feeder R1-12.47-3 has 

relatively low load so its maximum PV penetration as calculated from (1) is skewed high.

Fig. 1. Maximum feeder loads found by simulation vs. nominal feeder loads.

Fig. 2. A linear fit of nominal load to maximum feeder load found by simulation.

3. To reflect the stochastic nature of real loads, the load profiles were then randomized. Each of 

the 8760 scaled annual load values for each load point was multiplied by a factor sampled from 

a Gaussian (normal) distribution. The standard deviation of the Gaussian distribution was 0.2, 

and its mean value was 1.0. This resulted in a load diversity factor of about 1.3 for each load 

class. Each transformer feeds exactly one load, indicating that the creators of the feeders may 

0

2000

4000

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8000

10000

12000

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16000

18000

Load (kVA)

Simulated Max Load

Nominal Load

y = 0.9219x

R2 = 0.7878

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6000

8000

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14000

16000

18000

0 5000 10000 15000 20000

Nominal Load (kVA)

Simulated Maximum Load (kVA)

 

 
4 

have consolidated the feeder loads. To account for this consolidation a nominal residential load 

size of 5 kVA was assumed, and randomization was applied to each 5-kVA increment for 

residential transformers. No typical load size was assumed for commercial transformers because 

commercial loads vary widely in size. Hence the amplitude of random hour-to-hour fluctuations 

in commercial loads is much larger than for residential loads, and also larger than it would be in

a typical feeder. Some of the random variations in load profiles disappear when they are 

aggregated into a total feeder load profile. Randomizing loads after application of the scaling 

factor caused some minimum annual load voltages to drop below ANSI Range A, but remain 

within ANSI Range B, which reflects the conditions on physical feeders. Occasionally, 

randomization of loads caused overcurrents in the baseline (no PV) year-long simulation. In 

those cases, all loads on the feeder were reduced by 25% and the base case was re-simulated. 

Finally, a power factor of 0.9 was applied to all loads. Fig. 3 shows final scaled and randomized 

total load profiles (residential and commercial) for one feeder over two days, compared to the 

reference load profiles for the feeder's region.

Fig. 3. Total normalized residential and commercial loads for feeder R1-12.47-4 over two days (one

weekend and one weekday), plotted with the normalized residential and commercial reference 

load profiles for region 1. The total residential load follows its reference profile much more 

closely than the commercial load profile because this feeder has more residential transformers,

and because the residential transformers are randomized in 5-kVA increments. With just 12 

commercial transformers on this feeder, the largest transformers dominate the total load, so 

random variations applied to those loads lead to significant deviations from the reference load 

profile. 

B. PV location scenarios

After applying appropriately scaled and randomized load profiles, each feeder was simulated at various 

PV penetrations under several PV location scenarios. The scenarios studied include five distributed PV 

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

0 4 8 12 16 20 24 28 32 36 40 44 48

Normalized Load

Time (hours)

 

Total Residential Load

Reference Residential Load

Total Commercial Load

Reference Commercial Load
5 

scenarios and four scenarios with one PV system per feeder. The methodologies used to produce these 

nine PV location scenarios are as follows:

Distributed PV: The first five location scenarios all involve several distributed PV systems on the same 

feeder. In these scenarios, each PV system is installed at the location of an existing load and is scaled 

according to the load size and the desired PV penetration level. The distributed PV scenarios are:

1. PV clustered near the substation source

2. PV clustered near the midpoint of the feeder

3. PV clustered near the end of the feeder

4. PV evenly distributed throughout the feeder

5. PV randomly distributed throughout the feeder

To produce scenarios 1, 2, and 3, the existing load points on a feeder were sorted according to distance 

from the feeder source, where distance is defined as total conductor length from the source to the load 

in question. A PV system was added at the load point that best fits the desired location criterion, sized 

with peak PV power at 80% of the load's transformer rating. Another PV system was then added at the 

next-best-fitting load point, sized in the same way. This process continued until the desired PV 

penetration was reached. For example, to produce scenario 2 (PV near the midpoint), the load closest to

the middle of the feeder received PV first, then the load second-nearest to the middle of the feeder 

received PV, and so on, until the desired PV penetration was reached. For PV penetrations exceeding 

70%, the PV systems added to each load point were sized at 1.5 times the desired PV penetration 

multiplied by sf, multiplied by the respective load transformer rating.

To produce scenario 4, PV was added at all load points. The peak PV power was set equal to the desired 

PV penetration, multiplied by sf, multiplied by the applicable load transformer rating. As a result, each 

load point has a PV system sized in proportion to its transformer size to achieve the desired PV 

penetration.

To produce scenario 5, the various load points were sorted into a random order and PV was added to 

successive load points until the desired PV penetration was reached.

In all of scenarios 1, 2, 3, and 5, the size of the final PV system added was scaled down to achieve the 

desired PV penetration exactly.

Note that clustering PV near the end of a feeder does not necessarily result in PV systems that are 

physically or electrically close together. For example, in scenario 3, a feeder with two branches of 

approximately equal length would receive some PV near the end of each branch.

Single PV system: The remaining four location scenarios all involve a single, large PV system on a feeder. 

In these scenarios, the PV system was not installed at the location of an existing load, but rather was 

installed on its own transformer that was added specifically for the PV system. This transformer is not 

included in the total load transformer power. The single PV system scenarios are:

6. Single PV system close to the feeder source
6 

7. Single PV system near the feeder midpoint

8. Single PV system at the end of the feeder

9. Single PV system at a randomly selected point

To site the single PV system in scenarios 6, 7, and 8, all three-phase nodes on the circuit were sorted by 

distance from the feeder source and the PV system and its transformer were installed at the location 

that best fits the desired scenario. For example, to produce scenario 8, a single PV system and 

transformer were installed at the farthest three-phase node from the source. For scenario 6, the node 

where the PV system was installed was required to be at least 300 feet from the source to ensure that 

the system was downstream from the feeder substation components.

To produce scenario 9, the PV system and transformer were placed at a randomly selected three-phase 

node, again with the requirement that the node be at least 300 feet from the feeder source.

For each of these scenarios, the PV system was sized so that it alone would meet the PV penetration 

goal. The transformer was sized to have a rated apparent power 20% larger than the PV system peak 

rated power. During simulation of scenarios 6-9, current was monitored in the line immediately 

upstream from the PV system and compared to the continuous summer current rating of the line. 

Voltage was monitored at the PV system point of common coupling (and as in all scenarios, the voltage

at all loads and the status of all fuses were monitored). 

All PV systems simulated were installed at locations chosen by a computer algorithm that—to avoid 

introducing bias—did not evaluate the locations’ suitability for PV. For the distributed PV cases all load 

points were considered, and for the single PV system simulations all three-phase nodes were 

considered. 

C. PV penetration levels

For each of the nine scenarios and 16 feeders, GridLAB-D simulations were performed at PV

penetrations of 0% (the base case), 15%, 30%, and so on, with 15% steps until an overvoltage or 

overcurrent was detected at any point during the year. In cases where the PV penetration reached 

higher than 100% of peak load, the step size was increased to 50%. A bisection search was then 

conducted to define the maximum PV penetration more narrowly. The resolution of the bisection search 

for PV penetrations below 150% was 5 percentage points. Above 150% penetration, the resolution 

began rising based on the assumption that, for these very high penetration cases, the exact maximum 

penetration is not as relevant as the insight that maximum PV penetration is not limited by steady-state 

voltage or current. The maximum search resolution was 30 percentage points.

III. Distributed PV Results and Analysis

This section describes simulation results for the distributed PV location scenarios (scenarios 1-5). 

Scenarios 1 through 4 were simulated once for each feeder, and the random location scenario was 

simulated five times for each feeder.
7 

Table 1 lists the maximum PV penetration results for the various distributed PV scenarios. The number 

preceded by “R” in each feeder name indicates its geographical region. Values of maximum PV 

penetration obtained vary widely among the feeders, reflecting the diversity of physical feeder 

configurations. Maximum PV penetration also varies widely from one location to another on most 

feeders. All feeders tolerate at least 75% PV penetration in at least one case.

Table 1: Maximum PV Penetration for All Distributed PV Scenarios 

Maximum PV penetration for many feeder-location combinations reaches well over 100%. For these 

very large PV penetrations, it is likely that other effects not modeled in this study would limit physical PV 

penetration levels. For example, the taxonomy feeders do not include models of the substation 

transformer connecting the distribution feeder to the transmission system. This transformer's power 

rating would likely become a limiting factor in cases of very large PV penetration. Also, the transmission 

system is represented as an ideal voltage source in GridLAB-D, so any voltage rise it may experience due 

to very high PV penetrations is neglected. Similarly, dynamic concerns such as generator ramp rates are 

neglected. Other factors that are not addressed in this study and may limit PV penetration at moderate 

penetrations include protection, coordination, and power quality issues [7], [8]. Therefore, in very high 

penetration cases, it is more appropriate to conclude that steady-state voltage and current are not the 

limiting factors than that the feeder can actually tolerate such high levels of PV.

While in general maximum PV penetration results were quite high, several feeders, especially those in 

region 5, show relatively low limits to PV penetration. In general these feeders exhibited very high 

hourly average and maximum load voltages even when simulated without PV. The five feeders with the 

lowest limits to PV penetration (feeders R2-25.00-1, R5-12.47-4, R5-12.47-5, R5-25.00-1 and R5-35.00-1) 

all have maximum baseline (no PV) load voltages above 1.037 pu. The possibility that maximum baseline 

load voltages are high due to under-loading of these feeders by the loading methodology has been 

eliminated by examining minimum baseline hourly-average load voltages, which range from 0.96 to 0.99 

pu on these five feeders. Fig. 4 examines the relationship between maximum baseline feeder load 

Near Source Mid-feeder End of Feeder Evenly 

Distributed Minimum Maximum

R1-12.47-2 255 45 30 230 111 155 193 149 56 30 255

R1-12.47-3 243 230 218 255 255 255 255 255 255 218 255

R1-12.47-4 155 155 155 230 155 168 155 155 155 155 230

R1-25.00-1 380 255 130 280 205 230 243 255 280 130 380

R2-12.47-1 105 155 180 205 155 155 155 155 155 105 205

R2-12.47-2 205 205 168 218 168 205 168 180 168 168 218

R2-25.00-1 0 26 26 101 8 8 8 4 4 0 101

R3-12.47-2 155 155 205 180 180 180 168 168 155 155 205

R4-12.47-2 155 155 155 205 205 155 155 280 155 155 280

R4-25.00-1 155 155 105 205 155 180 155 155 155 105 205

R5-12.47-1 205 168 155 230 180 205 168 243 168 155 243

R5-12.47-2 94 90 83 105 90 98 94 98 94 83 105

R5-12.47-4 4 11 8 86 8 8 4 19 19 4 86

R5-12.47-5 8 4 34 86 15 15 4 45 30 4 86

R5-25.00-1 56 45 11 75 64 19 23 26 41 11 75

R5-35.00-1 8 0 0 75 0 11 15 0 0 0 75

Random Location

Feeder
8 

voltage and maximum PV penetration. The data in Fig. 4 suggest that while a high baseline voltage does 

not guarantee a low limit to PV penetration, a low limit is more likely.

Fig. 4. Maximum distributed PV penetration versus maximum baseline load voltage with linear fits shown for each 

location scenario.

Fig. 5 shows maximum PV penetration results by feeder for the non-random location scenarios. PV 

penetration limits are above 50% except for a few outliers. Most of the outliers correspond to the 

previously-identified five feeders where maximum and average baseline load voltages are relatively 

high. In addition to these feeders, two cases of maximum PV penetration below 50% remain: PV at midfeeder and end-of-feeder on R1-12.47-2. Notably, these are the same two outlier cases that appear in 

the lower left corner of Fig. 4. Both cases are limited by overcurrent conditions.

Fig. 5. Maximum PV penetration for all non-random, distributed location scenarios. Solid columns indicate PV 

penetration was limited by overcurrent; otherwise PV penetration was limited by overvoltage. One result over 

300% has been truncated. 

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0.99 1 1.01 1.02 1.03 1.04 1.05

Maximum PV Penetration (%)

Maximum Baseline Load Voltage (P.U.)

Near Source

Mid-feeder

End of Feeder

Evenly

Distributed

Even

End

Mid

Near

0

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Maximum PV Penetration (%)

Evenly Distributed

Near Source

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9 

For the feeders that exhibit low PV tolerance, all are most tolerant of evenly distributed PV. In fact, 

maximum penetration for evenly distributed PV is at least 75% in all cases. However, encouraging or 

enforcing the even distribution of PV on a feeder would likely be difficult in practice.

The five simulations involving randomly located distributed PV on feeder R1-12.47-2 all resulted in 

maximum penetrations above 50%, and four of the five were above 100%. In addition, the feeder's limit 

for single large PV systems was above 100% in all scenarios, indicating that the feeder does tolerate 

large amounts of distributed PV in most scenarios. The two cases of low maximum PV penetration on 

feeder R1-12.47-2 are due to overcurrent and appear to result from weak spots on smaller branches of 

the distribution feeder. For the mid-feeder case, voltage was not a problem until PV penetration was 

over 100%. For the end-of-feeder case, overvoltages occurred for PV penetrations above 34%, indicating 

that this feeder has a low tolerance for PV located far from the source from both voltage and current 

perspectives. 

Because switched capacitors can influence feeder voltages significantly, the relationship between 

maximum PV penetration and the presence of switched capacitors performing voltage control was also 

examined. No notable correlation was found.

IV. Single PV System Results and Analysis

This section describes simulation results for the PV location scenarios involving a single PV system per 

feeder (scenarios 6-9). Each of scenarios 6-8 was simulated once for each feeder, and the random 

location scenario was simulated nine times for each feeder.

Table II lists the maximum PV penetration results for all feeders and all single PV system scenarios 

simulated. The maximum penetrations in Table II tend to be higher than those found for the distributed 

PV scenarios. In several cases the maximum penetration was over 500% of peak load, which, for the 

reasons listed in Section III, is a much larger PV system than would be considered for installation. 
10

Table 2: Maximum PV Penetrations for all Single-System Scenarios 

The highest maximum penetration result was 1680% for the case of a single large PV system near the 

source of feeder R1-12.47-3. Feeder R1-12.47-3 was a lightly loaded feeder, so quantifying PV 

penetration relative to load (rather than some measure of feeder capacity) is partly responsible for the 

very high penetration value. The peak load of this feeder is 34% of total load transformer rating, so 

1680% of peak load represents 570% of the feeder's total load transformer rating, which is still a very 

high penetration. As mentioned in Section II, the single PV system installed in PV location scenarios 6-9 

is installed on its own new transformer (and this transformer's power rating is not included in the total 

load transformer rating). The rated peak DC power of the PV system is 9.2 MW, and the maximum 

measured AC output power of the PV system was 7.5 MW. The maximum measured currents on the 

three phases of the line immediately upstream from the PV system were 334, 325, and 333 A, which are 

just within the per-phase continuous summer current rating of the line, 334 A. The peak backflow power 

was approximately 7.1 MW. The rest of the feeder was therefore drawing 7.5-7.1 = 0.4 MW at the time 

of peak backfeed power. The nominal peak feeder load is 1.4 MW, and the simulated peak feeder load 

was 0.56 MW. The power going back into the substation is about 7.1 MW, or 5.1 times the nominal peak 

load. Therefore this feeder's maximum PV penetration for an installation located very near the source

would very likely be limited by substation equipment power and protection settings to a much lower 

value than that found here. The PV system was installed 472 feet from the feeder source, and the 

maximum voltage on the PV side of the transformer was 1.003 pu – reasonable given that very little 

voltage rise is expected over such a short distance.

Feeder R4-25.00-1 showed the same very high maximum PV penetration of 805% for all single PV 

system scenarios. The three-phase section of this feeder (which is the only section where our algorithm 

installed PV in scenarios 6-9) extends only about 1.2 miles and consists of a single line with one short 

branch. This line and its branch have the same continuous summer current rating of 530 A per phase 

over their entire lengths, and that current rating was the limiting factor in all single PV system scenarios, 

Near Source Mid-feeder End of 

Feeder Min. Max.

R1-12.47-2 155 255 270 255 755 255 255 255 255 755 530 755 155 755

R1-12.47-3 1683 655 708 1455 1455 780 655 705 655 880 1505 705 655 1683

R1-12.47-4 436 230 45 193 45 205 405 30 255 430 355 330 30 436

R1-25.00-1 955 280 139 580 280 405 680 1005 149 1005 955 630 139 1005

R2-12.47-1 230 45 56 94 79 56 30 180 15 41 15 56 15 230

R2-12.47-2 330 218 75 60 380 430 60 45 15 218 380 355 15 430

R2-25.00-1 255 180 94 56 205 155 180 60 205 230 155 105 56 255

R3-12.47-2 111 205 30 205 79 15 405 45 56 118 15 30 15 405

R4-12.47-2 355 105 430 330 255 30 90 45 330 155 355 180 30 430

R4-25.00-1 805 805 805 805 805 805 805 805 805 805 805 805 805 805

R5-12.47-1 280 305 45 75 305 15 255 30 305 60 255 193 15 305

R5-12.47-2 243 15 60 45 68 60 15 243 15 75 243 68 15 243

R5-12.47-4 330 130 60 86 49 45 155 118 111 45 38 26 26 330

R5-12.47-5 280 30 90 15 64 45 45 230 30 60 30 305 15 305

R5-25.00-1 168 124 94 83 45 180 15 136 136 71 180 15 15 180

R5-35.00-1 330 30 45 79 230 75 255 280 305 330 330 218 30 330

Random

Location

Feeder
11

leading to identical penetration limits in all cases. As in other very high penetration cases, unmodeled 

factors would limit PV penetrations to lower values than those found in this study. 

The range of maximum PV penetration results for each single PV system scenario tends to be wider than 

the range for distributed PV systems. The difference in ranges is more than expected based solely on the 

higher number of simulations performed. The wider range of PV tolerances reflects the variation in PV 

tolerance from one node to another in the feeder; a node that happens to be on the main feeder line is 

likely to have a much higher PV tolerance than a node on a small branch line. In contrast, a distributed 

group of PV systems becomes too large when any of the many affected points on the feeder experiences 

overvoltage or overcurrent; the variation from one group to another is smaller due to aggregation 

effects.

Compared to the distributed PV scenarios, more feeders showed minimum PV tolerances of less than 

30%. This is expected; putting a single PV system sized at more than 30% of the entire feeder's peak load 

on a small branch will cause voltage and/or current problems.

The relationship of maximum PV penetration to maximum baseline meter voltage was analyzed (Fig. 6). 

Again, the trend is for PV tolerance to decrease with increasing voltage, although there are more 

outliers than in Fig. 4, reflecting the high case-to-case variation in single PV system scenarios.

Fig. 6. Maximum single-system PV penetrations as a function of maximum baseline load voltage, with linear fits 

shown for each location scenario.

Simulations with single PV systems provide an opportunity to examine the relationship between 

maximum PV penetration and distance from the PV system to the feeder source. This relationship is 

shown in Fig. 7, where distance was measured by following the conductors back to the source. This 

shows a definite trend of decreasing PV tolerance with distance. There are, however, many exceptions 

to the trend. These exceptions are largely because some PV systems were installed on smaller feeder 

branches by the intentionally unintelligent PV location algorithm.

0

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0.99 1.01 1.03 1.05

Maximum PV Penetration

Maximum Base-Case Meter Voltage (p.u.)

Near source

Mid-feeder

End of feeder

Near

Mid

End
12

Fig. 7. Maximum PV penetrations plotted against conductor distance from PV system to feeder source, by 

geographic region.

Fig. 8 shows the maximum PV penetrations for each feeder under each non-random location scenario. 

Results over 500% are truncated to provide better resolution for more realistic penetrations. For single 

PV systems, more scenarios are limited by current than in the distributed PV scenarios. This is because 

the requirement that the system be installed at a three-phase node increases the probability of selecting 

a node near the trunk of the feeder where voltage is less likely to be an issue. 

0

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350

400

450

500

Maximum PV Penetration (%)

 

Near Source

Mid-feeder

End of feeder

Fig. 8. Maximum PV penetration for the 16 taxonomy feeders with single PV systems. Solid columns indicate PV 

penetration was limited by overcurrent and hatched columns indicate PV penetration was limited by overvoltage. 

Results over 500% are truncated.

0

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100

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300

350

0 10000 20000

Maximum PV Penetration

Distance from feeder source (ft)

Region 5

R5-12.47-1

R5-12.47-2

R5-12.47-4

R5-12.47-5

R5-25.00-1

R5-35.00-1

0

100

200

300

400

500

0 10000 20000 30000

Maximum PV Penetration

Distance from feeder source (ft)

Region 2

R2-12.47-1

R2-12.47-2

R2-25.00-1

0

500

1000

1500

2000

0 10000 20000

Maximum PV Penetration

Distance from feeder source (ft)

Region 1

R1-12.47-2

R1-12.47-3

R1-12.47-4

R1-25.00-1

0

300

600

900

0 5000 10000 15000 20000

Maximum PV Penetration

Distance from feeder source (ft)

Regions 3 and 4

R3-12.47-2

R4-12.47-2

R4-25.00-1
13

V. Conclusions

In this paper, several trends have been noted when considering maximum PV penetration relative to 

steady-state voltage and overcurrent: For distributed PV systems, maximum PV penetration was nearly 

always above 50% unless the feeder already exhibited maximum load voltages on the very high end of 

ANSI range A without PV. Maximum PV penetration generally decreases as the distance from the feeder 

source to the PV system increases, but most feeders still tolerate moderate to high PV penetrations 

even for PV systems near the end of the feeder.

Fig. 9 illustrates the general trend of very high PV tolerance with a few notable exceptions. In 86% of all 

PV location scenarios on all feeders, the maximum PV penetration was above 30%. In two-thirds of 

cases, the maximum penetration was greater than 90%. This does not indicate that two-thirds of cases 

will actually tolerate greater than 90% PV penetration, but rather that steady-state voltage and current 

are not limiting factors in approximately two-thirds of cases. While the 15% penetration rule of thumb

was found to be conservative in most cases (and sufficient in all single PV system cases), it was actually 

too high in 16% of the distributed PV cases.

Fig. 9. Percentage of simulated cases in which maximum PV penetration fell in various ranges for distributed PV 

(top) and single PV systems (bottom).

0.0%

10.0%

20.0%

30.0%

40.0%

50.0%

60.0%

70.0%

Percent of Cases in Range

0-15% 15-30% 30-45% 45-60% 60-75% 75-90% > 90%

Maximum PV Penetration Range

 

Distributed PV Systems

0.0%

10.0%

20.0%

30.0%

40.0%

50.0%

60.0%

70.0%

Percent of Cases in Range

0-15% 15-30% 30-45% 45-60% 60-75% 75-90% > 90%

Maximum PV Penetration Range

 

Single PV System per Feeder
14

References

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