1. Roger C. Dugan Fellow, IEEE Review of the Impacts of Distributed Generation on Distribution Protection 2015 IEEE Rural Electric Power Conference Asheville, NC April 20th-22nd, 2015 Robert F. Arritt Senior Member, IEEE

2. 2 Background This report focuses on the results of an industry survey EPRI has conducted on distribution protection practices to accommodate DG*. The ultimate goal of this survey was to review existing protection practices and determine what lessons have been learned. From this research, gaps/needs have been identified that will result in further EPRI research. *EPRI Survey on Distribution Protection: Emphasis on Distributed Generation Integration Practices. EPRI, Palo Alto, CA: 2013. 3002001277.

3. 3 Overvoltage Concerns 75% of participants selected overvoltages and islanding as biggest concern Events resulted in sustained overvoltages on the primary side of the substation transformer

4. 4 Interconnection Transformer Inverter based systemNon-inverter based system

5. 5 Ground Fault Overvoltage Testing 2014 EPRI Report: –Product ID: 3002003233 “Protecting the Modern Distribution Grid: Preliminary Inverter Characterization for Overvoltages” Delta / Wye Wye / Wye

6. 6 Protection Supervision Concerns Multiple events of inverters not turning on or cycling off due to overvoltages associated with high penetration. Reported problems of DG operators changing initial protection settings resulting in high voltages at PCC –Resulted in complaints from other customers of electronic equipment problems/failures SubstationEnd of Feeder ANSI Range A Lower Limit Distance Voltage ANSI Range A Upper Limit After DG Before DG

7. 7 Impacts of System Overvotages If you ever experienced any sustained primary overvoltages associated with DG interconnections, what was impacted, if anything? Surge arrester failure would be one expected consequence, particularly on US systems that exploited reduced insulation levels to apply lower-cost, lower- voltage arresters. Relay operation for overvoltages is also a common complaint, particularly for solar PV systems.

8. 8 Anti-Islanding How is anti-islanding being addressed? Have communications technologies been added to your system to communicate between the feeder relaying and interconnected DG? Note: No utilities that were interviewed actually use Rate of Change of Frequency (ROCOF) for islanding detection although 20% of respondents recognized it as an option for protection.

9. 9 Additional Gaps Identified Open-Phase protection –Some stated that it is the responsibility of the customer. –Some determined that it meets the requirements of IEEE Std 1547 the DG is able to protect against this event. –Two utilities identified open-phase concerns in commissioning tests.

10. 10 Conclusions The survey results found that DG interconnection protection practices vary significantly from utility to utility. Despite different practices, the basic objectives: –operate reliably and safely, –operate without degrading electric service to nearby customers, –and operate without compromising utility system integrity. By far, the protection issue of most concerns are islanding and overvoltages, in particular, overvoltages occurring following an islanding event.

11. 11 Continue testing with additional islanding scenarios, e.g. fault current contribution, islanding, open conductor, etc. Testing of additional inverter models to establish a representative sample Continue to build on the inverter models with improved test data. Provide model verification with this additional test data. 2015 EPRI Work Incorporate new modeling techniques to allow for additional inputs that impact inverter response. 2014 Tech update 2015 Technical Update Incorporate test results into the model to predict system response. Lab Testing

12. Together…Shaping the Future of Electricity