renewable energy workshop: california renewable dg integration study

©2014 Navigant Consulting, Inc.

DISPUT E S & INVESTI GATI O N S • ECONOMI C S • F INAN CI A L ADVISO RY • MANAGEM E N T CONSULT I NG

May 5, 2014

California Renewable DG Integration Study

Gene Shlatz | Director, Energy Practice

AWEA WINDPOWER 2014 AWEA Renewable Energy Workshop Las Vegas, NV

1 ©2014 Navigant Consulting, Inc. 1 ©2014 Navigant Consulting, Inc.

Agenda

• DG Study Objectives

• Analytical Framework

• Assumptions and Methods

• Study Results

• Key Findings

2 ©2014 Navigant Consulting, Inc.

» Background

– Governor’s Clean Energy Jobs Plan: Includes 12,000 MW of localized renewable energy (DG), generally defined as,

o 20 MW or less

o On-site or close to load

o Constructed quickly w/ no new transmission

» Study Purpose

– Gain a better understanding of infrastructure costs and impacts associated with increased DG installations in California, and how they change based on:

o interconnection location, distribution

o feeder characteristics, load types

o project size

– Develop a framework for a DG planning tool applicable for use by all California electric utilities

– Help achieve renewable DG goal of 12,000 MW by 2020

Project Overview:

California Renewable DG Integration Study: Study Objectives


“ As variable and distributed energy resource adoption reach significant levels this decade, new engineering and operating paradigms are required.

Resnick Institute, CalTech, Sept, 2012, Grid 2020 Towards a Policy of Renewable and Distributed Energy Resources.

“Estimates for fully capable distribution circuits suggest an additional cost of between $2 million and $3.5 million per circuit for physical upgrade and intelligent control systems.”

Electric Power Research Institute. April, 2011. Estimating the Costs and Benefits of the Smart Grid: A Preliminary Estimate of the Investment Requirements and the Resultant Benefits of a Fully Functioning Smart Grid.

The addition of up to 12,000 MW of renewable DG is expected to transform electric grid operations and impose additional costs.

. . . Accurate tools are needed to predict impacts and upgrades needed to ensure successful integration of renewable DG

Notable remarks:

California Renewable DG Integration Study: Background

The methods and tools applied in the CEC framework are

designed to predict DG impacts and integration costs with

reasonable accuracy for California utilities


DG installation are based on estimated totals for the Southern California Edison system – DG capacity additions will vary by utility.

Scenario DG Capacity

Renewable DG 2020 Target (CA Clean Energy Plan) 12,000 MW

Baseline DG Penetration (% DG assumed for SCE system) 4,800 MW

Maximum DG Penetration (25% over baseline) 6,000 MW

Minimum DG Penetration (50% below baseline) 2,400 MW

California Renewable DG Integration Study: DG Capacity


Many of the preferred locations for DG are located in high load density urban areas, where distribution feeders typically are shorter.

California Renewable DG Integration Study: Background (Utility System)

Urban: 8‐10,000 sq. miles = 15‐20% Rural: 40‐42,000 sq. miles = 80‐85%

(Nevada)

(Los Angeles)

Urban Customers: 75% Rural Customers: 25%


The framework is designed to contain the following features:

1. Has clear and easy to follow methods and assumptions

2. Contains sufficient analytical rigor to produce accurate results

3. Applies models and tools that are commonly used to simulate utility system operations

4. Uses processes that are understandable and repeatable for different scenarios

5. Includes Renewable DG technologies available to all California utilities and consumers

6. Uses evaluation criterion consistent with common industry practices and standards

7. Is expandable to include new DG technologies or solutions to address constraints

8. Produces results that clearly identifies all DG impacts and costs

Analytical framework designed and structured to be applicable to electric utility distribution systems throughout California.

California Renewable DG Integration Study: Analytical Framework


» Feeder selection – Based on statistical clustering approach

» Integration costs – Interconnection costs based on historical

averages and Navigant estimates

– Includes DG interconnection and distribution system upgrades

» Technology options – Mitigation/upgrades based on currently

available technology

– Near-term advanced technologies and solutions addressed (Smart Grid)

» Simulation approach – Commercially available load flow model

» DG interconnects to 33 kV, 16 kV, 12 kV, and 4 kV feeders

» IEEE 1547 Standards/Guidelines* – Based on requirements as of January 1, 2013

– Includes series of standards under 1547, where applicable

» Largest single DG unit is 20 MW – Most DG ≤ 10 MW because most feeders

rated ≤ 10 MW

Project team established guiding principles and assumptions to support the analytical framework.

California Renewable DG Integration Study: Project Assumptions

* IEEE Std 1547TM(2003)Standard for Interconnecting Resources with Electric Power SystemsP1547.1

DG benefits addressed in other ongoing studies


DG integration scenarios include a mix of mostly urban, mostly rural, and equal amounts of DG in each region

Three case studies evaluated using the analytical framework:

California Renewable DG Integration Study: Scenarios

Urban/ Rural DG 70% Urban

30% Rural

50% Urban

50% Rural

30% Urban

70% Rural

Urban DG (MW) 3,360 2,400 1,440

Rural DG (MW) 1,440 2,400 3,360

Total DG (MW) 4,800 4,800 4,800


» Navigant selected a subset of feeders that are representative of the entire system (~ 4,000 feeders)

– Feeder selection based on a statistical “clustering” technique to group feeders according to the following attributes:

o Urban and rural location

o Lower voltage (4.16 kV) versus higher voltage feeders (12.47/16/33 kV)

o Short and long feeders

o Primarily residential versus primarily commercial/industrial customers

o Light and heavy load density

» This set of feeders was used to simulate DG impacts given differences in:

– Feeder attributes

– Location

– Feeder loadings

An analytical approach is used to select a subset of distribution feeders to accurately represent the entire SCE system for DG modeling.

California Renewable DG Integration Study: Feeder Selection


Objective:

» Collect and analyze data on all distribution feeders (~4,000 ), covering approximately 30 different attributes, e.g., customer counts, loading, energy usage by rate class, line length, existing DG, etc.

» Goal: Identify a manageable set of feeders obtained from a ‘cluster’ of similar feeders, any of which can be represented by a single feeder

Process:

1. Select key attributes, and apply mathematical algorithm to determine the similarity between feeders across these attributes

2. Group feeders into ‘clusters’, each of which has unique characteristics

3. Next, examine the resulting clusters, and settle on a group of 13 to represent the entire distribution system

4. Select an “average” feeder from each cluster to represent a population of comparable feeders for DG integration studies

Feeder Selection Process



» Feeder groups are classified as urban or rural

» Feeder groups include a combination of short and long, and mix of customers and voltages


7 Urban Classifications 6 Rural classifications

1. Urban ~4 kV (788 feeders)

2. Urban 12-16 kV Residential (536 feeders)

3. Urban 12-16 kV Commercial (397 feeders)

4. Urban 12-16 kV Industrial (332 feeders)

5. Urban 12-16 kV Residential-Commercial

(1,160 feeders)

6. Urban 12-16 kV Long (20 feeders)

7. Urban 33 kV (13 feeders)

1. Rural ~4kV (82 feeders)

2. Rural 12-16 kV Short (113 feeders)

3. Rural 12-16 kV Medium (66 feeders)

4. Rural 12-16 kV Long (55 feeders)

5. Rural 12-16 kV Agricultural

(65 feeders)

6. Rural 33 kV feeders (12 feeders)

The analysis resulted in the selection of 13 feeders to represent the entire system of approximately 4,000 distribution feeders.

Many urban feeders have similar characteristics and attributes.

Urban Feeder 1 represents 788 urban feeders, whereas Rural

Feeder 6 only represents 12 feeders.


Rules adopted for the study include:

» DG output cannot exceed main line or lateral loading limits (load cannot offset DG output)

» DG is assumed off-line for up to 5 minutes following a circuit interruption (IEEE 1547)

» Inverter power factor is fixed; that is, not allowed to provide reactive support

» Load Tap Changer (LTC) and regulator operations must not materially increase the number of voltage regulator or LTC operations

» DG ride-through is not required for low voltage events

» Total allowable DG should recognize limits associated with load transfers via feeder ties, either for maintenance of reliability; i.e., cannot exceed feeder loading or voltage limits

Performance standards used to evaluate DG impacts based on industry standards, state regulations, and utility planning guidelines.

California Renewable DG Integration Study: Impact Analysis

The impact of intermittent renewable DG on bulk system

generation load following and frequency regulation is not

part of this study, but will be considered in future analyses and

investigations.


DG integration studies include impact on feeder voltage performance capacity, operational factors, and other potential requirements.

Category Description of Constraint or Requirement

Over/Under voltage Exceeds +/- 5 % from nominal

Line/equipment overloads Exceeds normal/emergency ratings

Voltage regulation Excessive regulator or load tap changer operation

Reverse power Reverse flow on mono-directional equipment

Fault duty Exceeds equipment ratings

Protection coordination Changes in settings or new devices

Operational constraints Load transfer constraints (e.g., for maintenance or

outage restoration)

Power quality Voltage flicker

Communications & SCADA For large DG or high penetration DG

California Renewable DG Integration Study: DG Impact Analysis

Additional analysis or data required to supplement feeder load flow studies


California Renewable DG Integration Study: DG Intermittency

Highly intermittent renewable output may create power quality violations on longer feeders.

LTC’s and voltage regulators typically do not respond

quickly enough to stabilize voltage.

0

20

40

60

80

100

120

140

160

12

:00

AM

12

:48

AM

1:3

6 A

M

2:2

4 A

M

3:1

2 A

M

4:0

0 A

M

4:4

8 A

M

5:3

6 A

M

6:2

4 A

M

7:1

2 A

M

8:0

0 A

M

8:4

8 A

M

9:3

6 A

M

10

:24

AM

11

:12

AM

12

:00

PM

12

:48

PM

1:3

6 P

M

2:2

4 P

M

3:1

2 P

M

4:0

0 P

M

4:4

8 P

M

5:3

6 P

M

6:2

4 P

M

7:1

2 P

M

8:0

0 P

M

8:4

8 P

M

9:3

6 P

M

10

:24

PM

11

:12

PM

Ou

tpu

t (k

W)

Output Profile (10 MW Ground-Based PV)

Minute-by-Minute PV Changes in Output Produces Significant

Voltage Swings

Output Profile (10 MW Ground-Based PV)

Ou

tpu

t (k

W)

Over 50% change

in PV output results

in highly variable

voltages where PV

is installed on the

end of longer

feeders


Study results must conform to utility design standards and operating practices, which includes non-static feeder configuration.

California Renewable DG Integration Study: Operational Considerations

Total connected DG after transfer is 16 MW, which

exceeds 10 MW limit by 6 MW.

(1) Normal conditions (feeder configuration) – Assume each feeder is able to

interconnect 10 MW of DG

(2) After sectionalizing and transfer for maintenance or outage restoration (A to B)

How DG is Impacted by Standard Operating Practices

S/S

A B

S/S

B B

DG DG

Open

Switch 8 MW 8 MW

S/S

A S/S

B X

Open

Bkr DG DG 8 MW

8 MW

Switch

Closed

B


Voltage regulation

equipment

Automation / SCADA

additions

Overload mitigation

(reconductoring)

Additional switches and

feeder ties

Feeder breaker

upgrades

Additional protective

devices

Protection upgrades

Additional

communication /

telecom

New distribution lines or

substations

Most options for mitigating DG impacts are based on traditional distribution solutions.

California Renewable DG Integration Study: Mitigation Options

The applicability of non-traditional, forward-looking solutions

such as active inverter controls and Smart Grid

(Managed/Interruptible DG) will be critical in the future to

enable greater amounts of DG capacity at lower cost.


California Renewable DG Integration Study: Integration Costs

Estimated DG integration cost ranges from a low of $600 million to a high of about $1.4 billion, with higher costs for greater amounts of rural DG.

Most costs are for upgrading rural feeders and

the installation of voltage regulating devices.

DG Distributed Uniformly on Feeders

Tota

l C

ost

($M

illio

ns)

$-

$200

$400

$600

$800

$1,000

$1,200

$1,400

70Urb/30% Rur 50Urb/50% Rur 30Urb/70% Rur

Interconnection System Upgrades

DG integration costs range from $190/kW to $270/kW for the distribution system


California Renewable DG Integration Study: Integration Costs

The costs of integrating DG increases significantly if clustered in large quantities, particularly when located near the end of longer feeders.

Most costs are for upgrading and installing new

rural feeders, upgrading urban feeders, and

installing voltage regulating devices.

Clustered DG

Tota

l C

ost

($M

illio

ns)

$-

$500

$1,000

$1,500

$2,000

$2,500

70Urb/30% Rur 50Urb/50% Rur 30Urb/70% Rur

Interconnection System Upgrades

DG integration costs range from $260/kW

to $420/kW for the distribution system


Key Takeaways:

» Cost of DG integration is highly dependent on where DG is installed. Integration impacts and costs are lower for DG installed in urban areas.

» DG integration costs vary as a function of key parameters and assumptions, including DG location on feeders and total installed capacity.

» DG integration costs increase significantly as greater amounts of DG are installed near the end of distribution lines.

» High penetration DG may require sophisticated communications and control systems to better manage DG impacts and reduce integration costs.

» Policies that “guide” or encourage DG in areas with fewer impacts would help achieve state renewables goals at lower cost.

The DG integration study produced a range of outcomes and integration costs.

California Renewable DG Integration Study: Key Findings & Takeaways


» Expand analytical framework to include transmission integration costs

» CEC to launch a state planning process pilot project that identifies and evaluates areas on the utility electricity system best suited to accommodate DG

Next Steps (2014)

California Renewable DG Integration Study: Next Steps

Key C O N T A C T S


Confidential and proprietary. Do not distribute or copy.

Key C O N T A C T S



Key C O N T A C T S



Key C O N T A C T S

©2014 Navigant Consulting, Inc. 21

Gene Shlatz | Director

Burlington, VT

+1.802.985.5216 direct

[email protected]

renewable energy workshop: california renewable dg integration study

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