The Host with the Most

EPRI Tool Helps Utilities Assess ‘Hosting Capacity’ on Distribution Systems

By Chris Warren

It was crunch time for Central Hudson Gas & Electric. On March 9, 2017, the New York Public Service Commission required the Poughkeepsie-based power company (along with other investor-owned utilities in New York) to create publicly available maps showing the hosting capacity of all distribution system feeders operating at 12 kilovolts and above, with a deadline of October 1, 2017. The commission wanted to clearly identify for the public the locations that could more readily host distributed energy resources (DER) without adverse grid impacts. For Central Hudson, new stand-alone solar projects of 2–5 megawatts were considered most likely to have significant impacts.

Central Hudson and the other investor-owned utilities in New York joined with EPRI to develop the maps. Using EPRI’s Distribution Resource Integration and Value Estimation (DRIVE) software, Central Hudson was able to calculate the hosting capacity of its approximately 230 distribution feeders operating at 12 kilovolts and above and completed the maps before the deadline. Released in 2016, DRIVE analyzes a distribution system’s hosting capacity at specific locations on individual feeders and provides detailed information on DER’s potential grid impacts, particularly related to grid reliability and power quality.

“Because New York’s investor-owned utilities all use different power flow modeling tools, it would have been difficult to develop a standardized methodology to compute the hosting capacity,” said Stephanie Genesee, associate engineer for electric distribution planning at Central Hudson. “We were pleased with the tool and grateful that EPRI was able to help us.”

Since then, Central Hudson has used DRIVE to update the maps annually. This year, they will include information on smaller areas on feeders known as nodes. In fact, all New York investor-owned utilities are using DRIVE to develop distribution system maps to indicate where it should be less costly to interconnect DER.

“Using DRIVE to compute hosting capacity is straightforward, and I can quickly train new engineers to use the tool,” said Genesee. “We also took the time to learn how the tool processes the data to better understand its functioning.”

The maps make business more efficient for New York’s solar developers as well. In the past, the utility was unable to provide applicants with insights on feeder hosting capacity without performing a detailed impact study. “Now we can refer developers to the map, which may indicate that one feeder has the potential to handle six megawatts while another may be able to handle only one megawatt. This gives developers guidance on which locations may be better suited to proceed with an interconnection project,” said Genesee. “We have received feedback from developers who say they use the maps and find them beneficial.”

Faster Interconnection, Integration with Other Utility Tools

Historically, solar installers and developers across the United States seeking to build new systems have had to submit applications to the utility for extensive reviews.

“It’s a time-consuming and expensive process,” said EPRI Technical Leader Matthew Rylander.

DRIVE is helping to change this by enabling utilities to quickly provide an approximation of whether new DER interconnections would result in distribution grid problems. This capability is particularly important as more regulators seek to streamline DER integration. New York’s Reforming the Energy Vision initiative aims to integrate DER into distribution planning and operations and includes a requirement that utilities identify where DER can best be accommodated. Regulators in Minnesota and California are pursuing similar efforts.

Through a feature called Connect, DRIVE helps utilities speed interconnection screening by linking to the utility websites that developers use to submit applications. The application data—including details on the size and type of DER—feed into DRIVE, which quickly determines if hosting capacity is available at the proposed location. “It will come back and indicate whether there is hosting capacity and how much,” said EPRI Senior Project Manager Lindsey Rogers. “If there’s no capacity, a utility engineer steps in and does a manual analysis to determine what upgrades are feasible, then contacts the developer who submitted the application.”

DRIVE can integrate data from other utility planning tools—such as power flow and generation of existing DER—to estimate potential voltage and thermal impacts of different sizes and types of additional DER at specific locations. “DRIVE was developed to work with different tools,” said Rylander. “Utilities have different distribution analysis software, and we wanted to create something that could work well on its own and with those tools.”

The tool can calculate hosting capacity feeder by feeder as well as location by location within a feeder—for current and future grid configurations. Utilities can use this capability to identify distribution system locations where DER can be interconnected without significant additional cost for infrastructure upgrades. This is valuable market information that can inform the planning of developers, regulators, and policymakers. Distribution planners can use DRIVE’s location-specific hosting capacity data along with load and DER deployment forecasts to assess necessary grid infrastructure upgrades.

“DRIVE enables users to input various parameters such as whether energy resources are solar or wind, how rapid are output fluctuations, and what additional fault current will come out of the system,” said Rogers. “Based on these analyses, the tool can inform users on impacts from various resources.”

While today DRIVE is used primarily to assess hosting capacity and DER’s grid impacts, EPRI plans to incorporate features to help planners estimate the grid benefits and values of siting and integrating new DER.

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