UL 1741 2023-05 PDF

Full title and description

St UL 1741 — Standard for Inverters, Converters, Controllers and Interconnection System Equipment for Use With Distributed Energy Resources (Edition published May 2023). This standard specifies construction, performance, and safety requirements and interconnection requirements for power conversion and control equipment used with distributed energy resources (DER) such as photovoltaic systems, energy storage systems, fuel cells, and small wind turbines, including grid-interactive and islanding behaviors.

Abstract

This edition of UL 1741 (May 2023) establishes requirements for the safety, performance, and anti-islanding functionality of inverters, converters, charge controllers and related interconnection system equipment intended for use with distributed energy resources. The standard addresses electrical, thermal, mechanical, and functional characteristics, including tests for electrical shock, grounding, insulation, protection from fire, overcurrent protection, abnormal operating conditions, interoperability with electric power systems, and requirements for grid support functions such as voltage and frequency ride-through, anti-islanding, and power quality.

General information

• Status: Current (as of May 2023 publication)
• Publication date: 2023-05
• Publisher: Underwriters Laboratories (UL)
• ICS / categories: 29.120.20 — Electrical equipment for power generation; categories include grid-connected inverters, DER interconnection equipment, electrical safety standards
• Edition / version: 2023-05 edition (revision of UL 1741 series)
• Number of pages: Varies by published file; typically 200–400 pages depending on annexes and incorporated requirements

Scope

UL 1741 covers inverters, converters, charge controllers, and other interconnection system equipment designed to transfer power between distributed energy resource sources and the electric power system, whether intended for utility-interactive operation or for islanded operation. The standard applies to equipment rated for line-to-line voltages and line currents typically used in distributed-generation applications and includes requirements for electrical safety, thermal performance, overcurrent and protection, grounding, insulation, enclosure integrity, and required functional tests such as anti-islanding, voltage/frequency ride-through, and controls necessary to support safe interconnection.

Key topics and requirements

• Safety construction requirements: insulation, creepage/clearance, enclosure protection, and wiring integrity.
• Electrical testing: dielectric withstand, leakage current, short-circuit and overload behavior.
• Protection and control: overcurrent protection, grounding, disconnecting means, and protective device coordination.
• Anti-islanding and islanding detection: test methods and performance criteria for preventing unintended islanding.
• Grid support functions: low/high voltage ride-through, frequency ride-through, ramping controls, and active/reactive power control for grid stability.
• EMC and power quality: limits for harmonic injection and electromagnetic compatibility requirements where applicable.
• Environmental and mechanical endurance: temperature, humidity, vibration, and mechanical strength testing.
• Marking, instructions, and documentation: required labeling, installation guidelines, and operational instructions for safe use.

Typical use and users

UL 1741 is used by manufacturers of inverters, converters, charge controllers, and interconnection system equipment for photovoltaic (PV) systems, battery energy storage systems (BESS), small wind, and other distributed generation technologies to design and certify products for safe utility-interactive and stand-alone operation. Other users include test laboratories, certification bodies, utilities, system integrators, electrical inspectors, and procurement/specification engineers who require products to meet recognized safety and interconnection requirements.

Related standards

Commonly referenced and related standards include IEEE 1547 (interconnection and interoperability requirements for distributed energy resources), NEC (National Electrical Code) articles for PV and energy storage systems, UL 1741 Supplement SA/SB/SI (grid-support requirements), IEC 62109 (safety of power converters for PV systems), and various UL/ANSI standards addressing electrical enclosures, connectors, and battery safety. Compliance with UL 1741 is often coordinated with local utility interconnection requirements and national regulations.

Keywords

UL 1741, inverters, converters, controllers, interconnection system equipment, distributed energy resources, DER, anti-islanding, ride-through, grid-interactive, photovoltaic (PV), energy storage, battery, safety standard, Underwriters Laboratories

FAQ

Q: What is this standard?

A: UL 1741 is a safety and performance standard for inverters, converters, controllers and related interconnection equipment used with distributed energy resources. The May 2023 edition reflects the current requirements and test procedures for safe interconnection and operation.

Q: What does it cover?

A: It covers construction, electrical safety, protection, functional performance (including anti-islanding and ride-through), environmental and mechanical testing, marking and instructions, and other requirements for equipment that connects DER to the electric power system or operates in islanded mode.

Q: Who typically uses it?

A: Manufacturers, test laboratories, certification bodies, utilities, system integrators, inspectors, and specifiers use UL 1741 to design, test, certify, install, and approve DER interconnection equipment.

Q: Is it current or superseded?

A: The version referenced here is the May 2023 edition. Whether it is current may depend on subsequent revisions or supplements published after that date; users should confirm the latest edition before applying requirements.

Q: Is it part of a series?

A: Yes. UL 1741 has a series of related supplements and amendments addressing specific functions (for example grid-support functionalities) and has been harmonized in part with IEEE 1547 requirements. Manufacturers often reference the base UL 1741 along with its supplements and regional/utility-specific requirements.

Q: What are the key keywords?

A: Key keywords include inverter, converter, controller, distributed energy resources (DER), interconnection, anti-islanding, ride-through, UL, safety, photovoltaic, energy storage, grid-interactive.