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Technical Interconnection, Codes, and Equipment Standards

To connect distributed PV (DPV) onto a grid safely, reliably, and cost-effectively requires utilities and customers to follow interconnection standards and codes, procedures, and equipment standards. These rules, procedures, and agreements collectively define the technical requirements for DPV systems to connect to the distribution network, the process for interconnection, and the parameters that DPV system components (e.g. inverter) must meet.

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Introduction

Interconnecting distributed PV onto a grid safely, reliably, and cost-effectively requires that utilities and customers must follow specific rules, procedures, and agreements. Interconnection standards and codes are typically a multi-step process that dictate where and how DPV can be connected to the grid (see figure below). In some cases, smaller, simple DPV systems may be eligible for an expedited (i.e. “fast-track”) review process. Technical screens are a set of basic questions that identify if a DPV system poses grid safety or reliability concerns. Larger systems that do not fit requirements or pass screens may have to be studied in detail to determine grid impacts and mitigation strategies. Interconnection standards are typically followed by a permitting process managed by a local jurisdiction. Equipment standards dictate the requirements of DPV components (e.g. inverter) to maintain system reliability.

 Interconnecting distributed PV onto a grid safely, reliably, and cost-effectively requires that utilities and customers must follow specific rules, procedures, and agreements. Interconnection standards and codes are typically a multi-step process that dictate where and how DPV can be connected to the grid (see figure below). In some cases, smaller, simple DPV systems may be eligible for an expedited (i.e. “fast-track”) review process. Technical screens are a set of basic questions that identify if a DPV system poses grid safety or reliability concerns. Larger systems that do not fit requirements or pass screens may have to be studied in detail to determine grid impacts and mitigation strategies. Interconnection standards are typically followed by a permitting process managed by a local jurisdiction. Equipment standards dictate the requirements of DPV components (e.g. inverter) to maintain system reliability.

Source: Energy Transition Initiative

 

Example Interventions

Power systems can address the challenges associated with integrating DPV into the grid through a variety of actions. The following suggested actions may help enable the scaling up of DPV.

Review and update interconnection standards and grid codes to clearly define the interconnection requirements for DPV generators and ensure their operating parameters support reliability in the distribution system. For example:

  • Require use of PV inverters with advanced functions such as fault ride-through, reactive power support, and voltage control to help maintain the grid’s frequency and voltage levels within utility standards.
  • Require distributed PV equipment that can remotely and selectively curtail system output when generation significantly exceeds demand at the substation level.
  • Require the use of commercially available battery inverters to enable off-grid operation of PV systems during grid outages.

In conjunction with interconnection standards, develop or update equipment standards to define the parameters that distributed PV components (e.g., inverters, converters, and controllers) must meet in order to contribute to reliability. Equipment standards can lay the foundation for testing, certification, and labeling programs for PV components that support interconnection standards.
Review and update interconnection procedures to create a standard and transparent process for interconnecting distributed PV in a way that balances the goals of increasing deployment with minimizing adverse impacts to the distribution system. For example:

  • Replace “first-come, first-served” interconnection processes with a transparent process based on system impacts.
  • Require PV inverters to comply with interconnection and equipment standards to enable interconnection screening procedures to be carried out quickly.

Establish technical screens that take into account impacts such as unintentional islanding (caused by high energy production during light feeder load), high voltage at the location of generation, potential for transient overvoltage occurrences, and impacts on the protection system coordination.

 

Reading List and Case Studies

Sun Screens Maintaining Grid Reliability and Distributed Energy Project Viability through Improved Technical Screens

Energy Transition Initiative, 2017

Interconnection processes ensure that DG systems are connected to the grid in a safe, reliable, and timely manner. This brief report reviews the U.S. Federal Energy Regulatory Commission’s (FERC) small generator interconnection procedures (SGIP) recommended screening for fast-tracking DG projects and presents efficient alternatives that support system reliability.


Processes and Timelines for Distributed Photovoltaic Interconnection in the United States

National Renewable Energy Laboratory, 2015

Time is a significant interconnection cost-driver for project developers, utilities, and local permitting authorities. Using data from over 30,000 residential and small commercial systems in the United States (both nationally and in five states with active solar markets), this report assesses timelines for application processing, construction, screening, and review. It also provides insights on some of the drivers of the interconnection process timeline, which can be used to inform the development of interconnection procedures.

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