Technical Interconnection, Codes, and Equipment Standards
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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.
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
Distributed Solar Quality and Safety in India: Key Challenges and Potential Solutions
National Renewable Energy Laboratory, USAID, Nexus Energytech Pvt Ltd, and Tetra Tech, 2020
This report provides solar quality and safety information and best practices that can help increase confidence in rooftop photovoltaic (RTPV) in India, particularly for small-capacity systems, and thus accelerate the growth of that sector. New data stemming from expert interviews and a stakeholder workshop shed light on common quality and safety technical issues at various stages of an RTPV system’s life and potential solutions for addressing them. To achieve the goal of a low-cost system with high energy yield, best practices must be followed at each stage of system life.
National Renewable Energy Laboratory
This site features educational materials on the Institute of Electrical and Electronics Engineers Standard 1547-2018 (IEEE Std 1547-2018) for interconnection and interoperability of distributed energy resources. The educational materials are for utilities, states, solar developers, transmission operators, regulators, policymakers, and other stakeholders.
Clause-by-Clause Summary of Requirements in IEEE Standard 1547-2018
National Renewable Energy Laboratory, 2020
This NREL technical report provides a quick reference guide to the technical requirements specified in the IEEE 1547-2018 standard. In addition to providing an overall summary of the standard's 11 clauses, the document also highlights the default and optional settings for parameters. Clause summaries include identification of the key stakeholders and, to a limited extent, the expected level of involvement they should have in decisions related to the implementation of the standard.
Building Blocks for Distributed PV Deployment, Part 2: Interconnection and Public Policy
National Renewable Energy Laboratory and USAID, 2018
This webinar, the second in a two part series, covers the key 'building blocks' of establishing a distributed PV program, which include:
- Creating interconnection processes, standards, and codes; and
- Providing public policy support as needed.
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.
Western Interstate Energy Board and National Renewable Laboratory, 2019
In recent years, the rapid adoption of customer-sited photovoltaics (PV) and other distributed energy resources (DERs) has led to a variety of innovations and new approaches in assessing costs, grid conditions, and requirements for interconnecting DERs to the grid. This report examines new policies and practices for interconnecting residential and commercial PV systems that are being implemented by states and utilities nationally to address emerging challenges with the increased volume of interconnection requests. Issues covered here include understanding and allocating costs, evaluating grid conditions to inform PV siting, interconnecting PV plus storage, automating processes, and requiring the availability of advanced-inverter functions that can address grid concerns with greater penetrations of distributed, inverter-based resources.
National Renewable Energy Laboratory, 2019
Deployment of distributed energy resources (DERs), in particular, distributed photovoltaics (DPV), has increased in recent years and is anticipated to continue increasing in the future. This report from the Distributed Generation Interconnection Collaborative (DGIC) was commissioned based on the need—identified through DGIC—for a central document summarizing considerations, practices, and emerging solutions across a broad set of topics related to DER interconnection. The report is targeted at a high-level, strategic-planning audience within utilities who are seeking an overview of DER interconnection issues and approaches and looking to understand how these may relate to their own situations.