Grid codes, interconnection, and safety

Safely, reliably, and cost-effectively connecting energy storage to the grid requires that utilities and customers follow interconnection rules that dictate both procedural elements and technical requirements. Collectively, these requirements define the technical requirements for storage systems to connect to the grid, the process for interconnection, and the parameters that storage system components must meet.

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These requirements differ depending on where the system is connecting (e.g. transmission system, distribution system), the system size, how the system will operate, and other factors. For the transmission system, because the number of interconnections is fairly low and the size of each system is fairly large, the interconnection of storage systems is typically handled on a ‘case-by-case’ basis with much more scrutiny than can be afforded to smaller, more numerous distributed interconnections. That said, regulators can require specific elements for all transmission-interconnection agreements. For the distribution system, however, there may simply be too many individual interconnections to review individually in detail. Furthermore, smaller systems do not tend to have the same level of technical impacts as larger, transmission-level systems. Many utilities have already created frameworks to process interconnection requests for DPV interconnections, and these same or similar technical criteria and processes  can be used to evaluate grid-tied energy storage systems (stand alone or connected to DPV), with some possible modifications depending on a system’s configuration, intended use case, and total export capacity.  


Typical Distributed Energy Resource (DER) (including storage) Interconnection and Permitting Process

 

Source: The value of storage providing peaking capacity doubles

 

 Reading List

Key Considerations for Adoption of Technical Codes and Standards for Battery Energy Storage Systems in Thailand 

National Renewable Energy Laboratory, 2021

This report presents global best practices of codes, standards, and interconnection procedures developed to support the safe and reliable deployment of battery energy storage systems BESS. Several relevant case studies highlight current efforts to ensure safe operation of BESS and showcase potential pathways for adoption of relevant codes and standards. Specifically, this report is intended to support the Thailand Office of Energy Regulatory Commission (OERC) and other stakeholders in their efforts to develop technical codes and standards to govern the installation and operation of BESS, but it may also be utilized as a guide for other countries as interest in the deployment of BESS technologies continues to grow.

Xcel Energy: Guidance No. 1 for the Interconnection of Electric Storage as Stand-Alone Sources, Parallel Operation for Customers without Generation, and in Parallel with Self-Generation

Xcel Energy, January 2017

This document outlines electric storage interconnection guidelines for three different configurations:

  • Case 1a: Stand-by energy storage — provision for facilities that require stand-by (backup) systems to provide power through onsite or grid-charged batteries.
  • Case 1b: Parallel Operation without onsite generation — provision for batteries without onsite generation to operate in parallel with utility
  • Case 1c: Parallel Operation with non-net metered, non-renewable onsite generation — provision for batteries with onsite generation to operate in parallel with utility.

 To ensure compliance with interconnection rules and to prevent the unintended export of power to the grid in cases 1b and 1c, meters and the appropriate control systems must be installed and registered. 

Example Interventions:

  1. Incorporating energy storage into interconnection processes, reducing uncertainty around their deployment behind-the-meter, and dictating how energy storage can charge and discharge.
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