Distributed Utility Associates












The Distributed Utility Integration Test (DUIT) is the first full-scale, integration test of commercial-grade, utility grid interactive Distributed Energy Resources (DER) in the United States. DERs are small modular generation and storage devices such as fuel cells, microturbines, photovoltaics and batteries that can be integrated into the utility electric system. Used in concert with the grid, DERs can lead to some or all of the following: lower energy bills/cost-of-service, superior service quality, high value energy services, and reduced environmental impacts. DUIT addresses a key technical issue: electrical implications of operating multiple, diverse DERs at high penetration levels within a utility distribution system.

DUIT is the next step in assuring the safe, reliable, and cost-effective inclusion of DER into the electric systems of the future. The goal is to advance the state of the art for DER integration practices and strategies. Other key objectives include a better understanding of the benefits and challenges associated with substantial DER penetration into the electric distribution system and gathering and analyzing data needed to characterize the actual value of DERs to ratepayers and to utilities.

Results and lessons learned from DUIT are expected to accelerate market acceptance of DERs by providing:

  • a testing ground for observing and measuring interactions between DERs and the electricity distribution system

  • knowledge needed to eliminate a key technical barrier of DER use as part of the power grid, demonstrating that DERs can operate in concert with grid safety

  • knowledge needed to quantify key benefits from integrating diverse DERs with utility distribution systems

  • data regarding viability of DERs connected on the customer side of the meter

Stakeholder Benefits


Consumers expect cost-effective electric systems that are safe, reliable, problem-free, and impose little or no damage to the environment. DUIT will enhance consumer confidence in distributed generation and storage technologies by demonstrating a mix of traditional and emerging DER technologies working together, in ways needed to provide the desired benefits.

DER Developers

Participating DER developers will acquire a better understanding of how their products work with the grid and other DERs. Developers will learn the utility perspective and how it affects acceptance of their products. Widely disseminated project information will provide an important opportunity for vendors to demonstrate their product’s performance to a broad audience.


Multi-megawatt implementation, testing and demonstration of DERs in an actual utility installation will provide real-world evidence that these technologies can be used as reliable utility resources to reduce cost of service, improve system operation, and to offer value-added services to customers.

Regulatory Agencies

DUIT will provide objective, real-world test conditions of DERs that offer significant value to federal, state and utility regulatory agencies, as they move to adopt standards and regulation for interconnection of DERs with the electric distribution system.

Test Program

A key aspect of DUIT is a thorough test of the feasibility and value of co-location and integration of DERs into the electric distribution system. A number of DERs, both generation and storage devices from multiple vendors, are installed within “electrical proximity” to each other so that a variety of electrical interactions may be observed, and operational implications can be evaluated. Commercial-grade “off-the-shelf” DER systems will be tested. These include

  • Combustion Turbines

  • Controls

  • Engines

  • Fuel Cells

  • Inverters

  • Microturbines

  • Photovoltaics

  • Electricity Storage

The collection of DERs will demonstrate the feasibility of remote operations, monitoring and dispatch. Individual DERs will be instrumented to measure interaction with the grid. The gathered data will be analyzed to characterize the impact and actual value of DERs to ratepayers and utilities.

DUIT participation is open to all primary stakeholders, regulators, DER developers and vendors, and utilities. DER vendors, especially, are encouraged to participate as a way to demonstrate the viability of their products.

Test Protocols

Each protocol represents multiple tests across DR devices

  • Abnormal Conditions

  • Adjacent Feeder Faults

  • Anti-Islanding

  • Capacitor Switching

  • Cold Load Pick-up

  • Control Strategies

  • Fuse Coordination

  • Network Systems

  • Intentional Islanding

  • Power Quality

  • Reclosing Coordination

  • Synchronization

  • Short Circuit Current

  • Stability

  • Substation Backfeed

  • Sectionalizer Test

  • Voltage Regulations

Anti-islanding tests identified as having highest priority for Phase 1 of the DUIT testing.

Current Testing

Anti-Islanding Test Plan
Test Description and Sequence

Basic Islanding Test

Individual Unit Testing


Islanding with Multiple DRs

Homogeneous Groups

Small Groups



Non-Linear Loads, Anti-islanding Tests

Individual Units


Islanding with Dynamic Load:Generation Ratios

Individual Units


Anti-islanding with Rotating Loads

Individual Units


Harmonic Content due to Anti-islanding Schemes

Individual Units


Voltage/Frequency Trip Settings

Individual Units

Homogeneous Groups

Small Groups


Test Result

Please allow active content to view these presentations (.ppt)

2004 CEC Results Presentation

Single-Unit Islanding Test Typical Unit Results

Close Out Meeting

DUIT Sponsors and Participants

DUIT is a public-private collaboration among DER technology companies, government agencies and utilities. These organizations are contributing equipment, expertise and financing.

Current sponsors and participants include:

  • Beacon Power

  • California Energy Commission

  • Capstone Turbines

  • Caterpillar

  • Consolidated Edison

  • Cummins Power Generation

  • Distributed Utility Associates


  • Endecon Engineering

  • EPRI

  • Exelon

  • Pacific Gas & Electric (PG&E)

  • NREL

  • Sacramento Municipal Utility District (SMUD)

  • Salt River Project

  • San Francisco Public Utility Commission

  • SMA America

  • Solar Turbines

  • Texas Public Utility Commission

  • US Department of Energy

  • Underwriters Laboratory

  • Xantrex

  • ZBB

DUIT seeks to evaluate a diverse group of DER technologies/products. Vendors targeting the DER market are invited to contact the DUIT team regarding participation.

Other Links

California Energy Commision (CEC)


DUIT Photos

Learn More about DUIT

To inquire about prospective DUIT project participation, technical specifications, test plans, project plans or the DUIT white paper, please contact the DUIT Project Team.

Susan Horgan

DUIT Project Leader

Distributed Utility Associates

Tel: (925) 447-0625

[Send Email]










Related Sites

California Energy Commission (CEC)

National Renwewable Energy Laboratory (NREL)

Electricity Storage Association


Department of Energy

Office of Electric Transmission and Distribution

Recommended Readings

Risk and DR: Coin of the Realm

EPRI-DOE Handbook of Energy Storage for Transmission and Distribution Applications

DER Benefits Study Comparison, NREL 2003

CEC RFP Attachment 14: Electric Energy Storage Benefits and Market Analysis

Distributed Resources: A How-To Guide for Federal Facility Managers

Economic Analysis of Distributed Energy Impacts, DOE 2003

Congressional Testimony on DU

Texas Distributed Generation Interconnection Manual

Utility Owned Distributed Generation Market Potential

Analysis of the Economic and Environmental Benefits of Market Penetration of Distributed Generation

Bulk Energy Storage for Cooperatives

Innovative Business Cases for Energy Storage in a Restructured Electricity Marketplace, Phase II

Innovative Applications of Energy Storage In a Resrtuctured Electricity Marketplace, Phase III