3.7 Interoperability, DER Interconnection, and Communication Standards and Technologies

3.7.3 UL 1741 and IEC 62109 Certification Testing for Product Safety

UL 1741 is a product safety standard that defines the testing and certification requirements for DER systems that must meet the IEEE 1547 requirements. This UL1741/IEEE1547 combination of requirements is used to evaluate grid tied DG products for both electrical safety and utility interconnection.

The standard covers PV systems, fuel cells, microturbines, wind and hydro turbines, engine gen-sets, and other inverter-based DER systems. In many jurisdictions, compliance with UL 1741 testing is mandatory for certifying that these DER systems meet the interconnection requirements.

The areas covered UL 1741 include electrical ratings requirements for components, electrical and environmental requirements for enclosures, and electrical spacings. It also addresses fire hazards related to operating temperatures, short-circuit situations, and overload conditions. Software is also certified and tested, since it is viewed as the main critical component of a utility interactive inverter as the software often controls most of the utility interaction of the inverter.

As DER certification and testing has become increasingly important worldwide, the US is moving to adopt IEC 62109.  IEC 62109 was born out of UL1741 and was expanded / updated to address cutting edge safety aspects of PV power conversion equipment.  UL was granted rights to develop UL 62109-1 & UL62109-2; UL62109-1 has been published and UL62109-2 is expected to be published Q1 2015. These will then become the equivalent IEC 62109-1 and -2 standards.  Although IEC 62109 is focused only on PV systems, it can be applied to other inverter-based DER systems.