Solar

Preparing for more DG on the grid: No two-way power flow about it?

Installing solar panels seems simple, according to all those companies selling them. Just sign up, invite someone onto your roof to install them, and boom, you're in business — generating power even when the grid goes down. Right? Not exactly.

There are rules governing grid connections and often distributed generators — homes or businesses generating power to primarily meet their own needs. A house with rooftop solar, for example, isn't allowed to produce power when the grid is down. The generator must also apply to connect to the grid, and then a utility must manage how that generation source is integrated into its distribution system.

As more customers generate some of their own power, utilities are watching for effects to their distribution systems, especially as two-way power flow increases. Meanwhile, for customers, connecting to the grid may be easy for early adopters, but the process can slow down as utilities and governing bodies get overloaded with applications.

Breaking the Camel's Back
The varying size and territory of utilities makes their concerns with distributed generation unique. But in the process of working with and interviewing hundreds of utilities on distributed generation interconnections, Michael Coddington has discovered some common themes. Coddington is a principal engineer in the integrated systems group at the National Renewable Energy Laboratory's Power Systems Engineering Center. The concerns he's heard the most have to do with voltage control, grid protection, reverse electricity flow and unintentional islanding.

"Some of the most common concerns for utilities are that distributed generation could have a negative impact on the utility system," Coddington said. Each one of these factors could be the straw that breaks the camel's back — the voltage spike that causes an outage. "Solar and distributed resources in great enough quantity could cause high voltage on the grid which is potentially damaging to the customer load."

Sure, the grid has protections in place — fuses and circuit breakers. These devices are coordinated, but they were set up for a grid that serves homes, not a grid that receives power. If an outage occurs, a utility's goal is to contain it to affect the smallest number of customers. But because distributed energy puts power back on the grid, it can negatively impact those protections, Coddington said.

As many engineers will tell you, the power grid was never designed for electricity to flow both ways. Coddington said this is why reverse flow raises a slew of concerns.

And while rooftop solar customers may think they can go "off the grid" thanks to their own power source, that's called unintentional islanding and it's to be avoided. Planned islands, like hospitals with generators, have been around for ages, said Tom Stanton, principal researcher for energy and environment at the National Regulatory Research Institute. But those planned islands don't try to power the block next to them when the power is out, which is what could happen with a solar system unintentionally left online while the rest of the grid is down.

Interconnect and Integrate
Coddington and Stanton together have been studying how utilities and states are working to improve interconnection and integration processes. The duo made a presentation to the National Association of Regulatory Utility Commissioners in February at the group's annual winter conference in Washington.

Some utilities are already using fast, reliable distribution system modeling to keep tabs on all major distributed energy resources in their service territories, Stanton and Coddington said. These utilities may also be using easily accessible maps that show substation and feeder hosting capacity — a way to monitor the straws on the camel's back, so to speak.

These maps can help focus attention on low-cost and good-better-best locations for installing distributed generation. Utilities also have more and better mitigation techniques at their fingertips that can enable more distributed generation on existing circuits. Meanwhile, Coddington is engaging directly with the Institute of Electrical and Electronics Engineers and Underwriters Lab to look at the changes that are starting to take place around the standards for interconnection based on inverter capabilities.

But the work is not for utilities and safety organizations to do alone. States are implementing processes and procedures that make for best practices industry wide, Stanton said. States that have seen an influx of distributed generation — such as California, Arizona and Hawaii — have served as test cases for new regulations. These states and others are already using uniform state rules and procedures for all utilities, employing online and electronic interconnection applications, streamlining a transparent process with open communication between utilities and developers, and tracking project applications with simple, reliable systems.

Preparing Customers
With regulators streamlining procedures and utilities mapping distribution systems, one important piece remains: educating customers. Taking note of the emerging trend toward solar and other distributed energy resources, wholesale energy supplier American Municipal Power Inc. is supplying its member public power utilities with a manual to prepare them for customer inquiries about distributed energy devices.

AMP published the 75-page Focus Forward Member Toolkit in late 2016 as a guide to distributed energy resources that addresses national trends impacting the electric industry. The manual focuses on customer-owned generation, rates and interconnections.

"We wanted to be as proactive as possible in helping our members prepare," said Jolene Thompson, AMP's executive vice president of member services and external affairs. "We've received a number of inquiries from our members over the past year about customer-sited generation, and that led the AMP Board of Trustees and executive team to formulate a strategic approach. You don't want to be in a position where you haven't thought about it. Try to be ahead of the game, if you can."

AMP, based in Columbus, Ohio, is a joint action agency that supplies power and services to more than 130 public power utilities in Ohio, Pennsylvania, Michigan, Virginia, Kentucky, West Virginia, Indiana and Maryland, and to the Delaware Municipal Electric Corporation, a sister joint action agency.

AMP worked with consultants to compile the member toolkit. The manual includes an interconnection checklist. The manual also emphasizes the importance of engaging stakeholders — including customers — when designing a distributed resource program.
AMP's manual is available online for its members. The American Public Power Association is also offering resources and tools to member utilities nationwide through its Public Power Forward initiative. Access them at PublicPower.org under Topics and Public Power Forward.

Public Power Forward: Top 5 Resources for the Utility of the Future

Public Power Forward Roadmap
Do you wonder about the path toward a new era in electricity? This map addresses changing customer service preferences, technologies, regulations and market forces.

Residential Consumers and the Utility of the Future
The utility isn't the only one in the community worrying about how things are changing; it's customers, too. This white paper identifies the top consumer concerns with policy initiatives that stimulate growth in distributed generation as well as changes in rate design.

Grid Modernization Roadmap
In response to the Smart Electric Power Association's 51st State Initiative, this guide lays out the current and future state of public power with actionable transition steps.

Rate Design
If your utility has ever considered the impact of distributed generation on its revenue recovery, check out these rate design options and the pros and cons of each approach. The paper is accompanied by an infographic of the top 10 questions your utility should ask before implementing new rates.

Value of Solar Primer
We get it: Valuing solar power on the grid is hard. Different studies have produced different results. Find out why and dig into the pros and cons of adapting a value of solar tariff.

 

 

Topics