Think about, for a second, what the grid of the not-too-distant future appears like. Ought to present traits proceed, you’ll doubtless discover extra electrical automobiles gliding silently by the streets. You may even see extra buildings in your neighborhood topped with a photo voltaic array, lots of them backed up with power storage. Need scorching water or cool air? There’s a very good probability these home equipment are powered by electrons as an alternative of liquid fuels. Throughout the board, good distributed power sources (DERs) have gotten ubiquitous.
This isn’t at present’s actuality for most individuals, however momentum towards this imagined electrical future is difficult to disregard, which begs questions like: How can we clean out the transition to a extra decentralized grid with probably hundreds of thousands of controllable property? How can electrical programs of all scales–from particular person buildings to regional grids–be optimized to deal with extra capability?
One of many largest items to the puzzle will likely be energy management programs (PCS) able to monitoring and controlling each sources and masses in real-time. Proper now, there isn’t a formal UL itemizing for PCS, solely a restricted “certification requirement determination” (CRD) looped right into a separate customary. However that’s about to vary with the discharge of the brand new UL 3141 customary, as we’ll clarify on this article.
What’s a PCS?
A PCS is a system–not essentially a singular system–designed to take care of secure ranges of present and loading on busbars. The system consists of a controller plus sensors and a technique of communication between the controllable masses and sources. In lots of instances, the PCS will likely be its personal product. In some instances, the PCS is built-in inside an inverter.
There are lots of methods to configure a PCS. The instance solar-plus-storage system beneath aggregates many PV and ESS inverters earlier than interconnecting with an ordinary 200 A residential important breaker.
Present transformers (CTs) monitor present on the aggregation panel and the principle service panel. Communication cables join the controller to the CTs and all inverters. When the CTs sense {that a} busbar is approaching overload, they ship alerts to throttle down the PV or ESS inverters.
A correctly configured PCS can allow the oversizing of era sources effectively past the load-side supply connection sizing constraints of NEC Article 705.12. One other widespread utility is utilizing a PCS to manage energy flows from the a number of inverters (PV inverter, power storage inverter, and so on.) that make up an AC-coupled solar-plus-storage system. The identical logic applies to programs that combine EV chargers or different controllable masses and sources. If we return to our unique thought train, it’s simple to see how the more and more complicated electrical infrastructure of the close to future will profit from the capabilities a PCS affords.
PCS and the Nationwide Electrical Code
The time period “energy management system” first appeared in Part 705.13 of the 2020 Nationwide Electrical Code (NEC) and was solely used to explain programs that management sources.
705.13 Energy Management Programs.
An influence management system (PCS) shall be listed and evaluated to manage the output of a number of energy manufacturing sources, power storage programs (ESS), and different tools. The PCS shall restrict present and loading on the busbars and conductors provided by the PCS.
For the circuits linked to a PCS, the PCS shall restrict the present to the ampacity of the conductors or the scores of the busbars to which it’s linked in accordance with 705.13(A) by (E).
Subsections (A) by (E) go on to element monitoring, overcurrent safety, and settings restrictions necessities. Most notably, entry to the PCS settings is restricted to “certified personnel” for safety functions. Whereas not explicitly spelled out within the Code, in follow, this implies settings will likely be configured and locked in at commissioning. Adjusting settings post-commissioning will typically contain assist from the producer.
The 2023 NEC launched new language to Part 705.13, changing “energy management system” with “power administration system” (EMS), a time period that has been lengthy outlined in Code in Article 750. The important thing distinction between a PCS and EMS is {that a} PCS is programmed to optimize security and efficiency, whereas an EMS was traditionally programmed to optimize financial outcomes. A PCS would modify inverter output to restrict overloading busbars; an EMS would modify inverter output to maximise ROI by utility time-of-use charges. An EMS with PCS would carry out each capabilities.
705.13 Power Administration Programs (EMS).
An EMS in accordance with 750.30 shall be permitted to restrict present and loading on the busbars and conductors provided by the output of a number of interconnected electrical energy manufacturing or power storage sources.
Informational Observe: A listed energy management system (PCS) is a kind of EMS that’s able to monitoring a number of energy sources and controlling the present on busbars and conductors to forestall overloading. See UL 1741, Inverters, Converters, Controllers and Interconnection System Gear for Use with Distributed Power Sources, and UL 916, Power Administration Gear, for info on PCS and EMS.
It needs to be famous that the language used to distinguish PCS, EMS, and “power administration” extra broadly continues to be fuzzy. But when we squint somewhat, we are able to begin to see the place every expertise is headed and the way they’ll work collectively. The inclusion of “listed PCS” within the 2023 NEC created an allowance for an EMS that might carry out security capabilities along with conventional EMS capabilities. Anticipate additional clarifications within the 2026 NEC.
PCS Itemizing Requirements
The Informational Observe tucked into 705.13 features a reference to UL 1741, the itemizing customary for grid-tied PV and power storage inverters, converters, controllers, and different DER interconnection tools. If we observe this breadcrumb path, we’ll discover that there isn’t a specific itemizing for PCS, solely a Certification Requirement Determination (CRD – final acronym, I promise).
A CRD is an approximation of an upcoming customary for a cutting-edge product that doesn’t at present have its personal customary. It acts as proof that unbiased take a look at labs have evaluated new applied sciences, and a bridge to a extra formal customary sooner or later. For instance, the second version of the UL 1741 itemizing customary included a CRD for non-isolated (ungrounded) inverters. These CRD necessities had been later absorbed into the third version of the UL 1741 customary as soon as non-isolated inverters grew to become the norm.
As we speak, A PCS producer can determine whether or not to check their product to the UL 1741 CRD. Since it’s the solely take a look at customary out there as of this writing, many producers will choose to take action and can embody the “UL 1741” or “UL 1741 CRD-PCS” on their datasheets.
As of January 2024, UL has begun growing a wholly new customary particularly for PCS. The UL 3141 Define of Investigation for Energy Management Programs is essentially primarily based on the unique UL 1741 PCS-CRD however is meant to deal with many different kinds of PCS tools and purposes. One utility distinctive to PCS is service improve avoidance and feeder overload management, which evaluates a product’s skill to make sure feeder and repair conductors are usually not overloaded by load and/or supply management.
The event of the brand new UL 3141 customary will likely be necessary to offer tools producers and different stakeholders with confidence that PCS merchandise sooner or later will likely be evaluated for reliability and security as principal necessities for itemizing.
The second version of UL’s Define of Investigation for Energy Management Programs will likely be printed this yr, adopted by the formal, consensus UL 3141 customary in 2025 or early 2026. We encourage you to trace UL updates and submit public suggestions if you wish to be concerned within the drafting course of.
Conclusion
At a sure level, the widespread adoption of distributed power sources turns into an optimization downside that’s solvable with energy management programs. Whether or not a enterprise proprietor needs to impress operations with out a main service improve or a public utility hopes to keep away from pricey transmission upgrades by controlling hundreds of small, grid-tied masses and sources, electrical programs of all scales have gotten smarter and safer by integrating PCS. As these revolutionary applied sciences evolve, anticipate codes and requirements to observe swimsuit.
Be taught extra about UL 3141 on the Mayfield Renewables Schooling Summit in Austin, Texas. Click on right here for occasion particulars and registration.
Think about, for a second, what the grid of the not-too-distant future appears like. Ought to present traits proceed, you’ll doubtless discover extra electrical automobiles gliding silently by the streets. You may even see extra buildings in your neighborhood topped with a photo voltaic array, lots of them backed up with power storage. Need scorching water or cool air? There’s a very good probability these home equipment are powered by electrons as an alternative of liquid fuels. Throughout the board, good distributed power sources (DERs) have gotten ubiquitous.
This isn’t at present’s actuality for most individuals, however momentum towards this imagined electrical future is difficult to disregard, which begs questions like: How can we clean out the transition to a extra decentralized grid with probably hundreds of thousands of controllable property? How can electrical programs of all scales–from particular person buildings to regional grids–be optimized to deal with extra capability?
One of many largest items to the puzzle will likely be energy management programs (PCS) able to monitoring and controlling each sources and masses in real-time. Proper now, there isn’t a formal UL itemizing for PCS, solely a restricted “certification requirement determination” (CRD) looped right into a separate customary. However that’s about to vary with the discharge of the brand new UL 3141 customary, as we’ll clarify on this article.
What’s a PCS?
A PCS is a system–not essentially a singular system–designed to take care of secure ranges of present and loading on busbars. The system consists of a controller plus sensors and a technique of communication between the controllable masses and sources. In lots of instances, the PCS will likely be its personal product. In some instances, the PCS is built-in inside an inverter.
There are lots of methods to configure a PCS. The instance solar-plus-storage system beneath aggregates many PV and ESS inverters earlier than interconnecting with an ordinary 200 A residential important breaker.
Present transformers (CTs) monitor present on the aggregation panel and the principle service panel. Communication cables join the controller to the CTs and all inverters. When the CTs sense {that a} busbar is approaching overload, they ship alerts to throttle down the PV or ESS inverters.
A correctly configured PCS can allow the oversizing of era sources effectively past the load-side supply connection sizing constraints of NEC Article 705.12. One other widespread utility is utilizing a PCS to manage energy flows from the a number of inverters (PV inverter, power storage inverter, and so on.) that make up an AC-coupled solar-plus-storage system. The identical logic applies to programs that combine EV chargers or different controllable masses and sources. If we return to our unique thought train, it’s simple to see how the more and more complicated electrical infrastructure of the close to future will profit from the capabilities a PCS affords.
PCS and the Nationwide Electrical Code
The time period “energy management system” first appeared in Part 705.13 of the 2020 Nationwide Electrical Code (NEC) and was solely used to explain programs that management sources.
705.13 Energy Management Programs.
An influence management system (PCS) shall be listed and evaluated to manage the output of a number of energy manufacturing sources, power storage programs (ESS), and different tools. The PCS shall restrict present and loading on the busbars and conductors provided by the PCS.
For the circuits linked to a PCS, the PCS shall restrict the present to the ampacity of the conductors or the scores of the busbars to which it’s linked in accordance with 705.13(A) by (E).
Subsections (A) by (E) go on to element monitoring, overcurrent safety, and settings restrictions necessities. Most notably, entry to the PCS settings is restricted to “certified personnel” for safety functions. Whereas not explicitly spelled out within the Code, in follow, this implies settings will likely be configured and locked in at commissioning. Adjusting settings post-commissioning will typically contain assist from the producer.
The 2023 NEC launched new language to Part 705.13, changing “energy management system” with “power administration system” (EMS), a time period that has been lengthy outlined in Code in Article 750. The important thing distinction between a PCS and EMS is {that a} PCS is programmed to optimize security and efficiency, whereas an EMS was traditionally programmed to optimize financial outcomes. A PCS would modify inverter output to restrict overloading busbars; an EMS would modify inverter output to maximise ROI by utility time-of-use charges. An EMS with PCS would carry out each capabilities.
705.13 Power Administration Programs (EMS).
An EMS in accordance with 750.30 shall be permitted to restrict present and loading on the busbars and conductors provided by the output of a number of interconnected electrical energy manufacturing or power storage sources.
Informational Observe: A listed energy management system (PCS) is a kind of EMS that’s able to monitoring a number of energy sources and controlling the present on busbars and conductors to forestall overloading. See UL 1741, Inverters, Converters, Controllers and Interconnection System Gear for Use with Distributed Power Sources, and UL 916, Power Administration Gear, for info on PCS and EMS.
It needs to be famous that the language used to distinguish PCS, EMS, and “power administration” extra broadly continues to be fuzzy. But when we squint somewhat, we are able to begin to see the place every expertise is headed and the way they’ll work collectively. The inclusion of “listed PCS” within the 2023 NEC created an allowance for an EMS that might carry out security capabilities along with conventional EMS capabilities. Anticipate additional clarifications within the 2026 NEC.
PCS Itemizing Requirements
The Informational Observe tucked into 705.13 features a reference to UL 1741, the itemizing customary for grid-tied PV and power storage inverters, converters, controllers, and different DER interconnection tools. If we observe this breadcrumb path, we’ll discover that there isn’t a specific itemizing for PCS, solely a Certification Requirement Determination (CRD – final acronym, I promise).
A CRD is an approximation of an upcoming customary for a cutting-edge product that doesn’t at present have its personal customary. It acts as proof that unbiased take a look at labs have evaluated new applied sciences, and a bridge to a extra formal customary sooner or later. For instance, the second version of the UL 1741 itemizing customary included a CRD for non-isolated (ungrounded) inverters. These CRD necessities had been later absorbed into the third version of the UL 1741 customary as soon as non-isolated inverters grew to become the norm.
As we speak, A PCS producer can determine whether or not to check their product to the UL 1741 CRD. Since it’s the solely take a look at customary out there as of this writing, many producers will choose to take action and can embody the “UL 1741” or “UL 1741 CRD-PCS” on their datasheets.
As of January 2024, UL has begun growing a wholly new customary particularly for PCS. The UL 3141 Define of Investigation for Energy Management Programs is essentially primarily based on the unique UL 1741 PCS-CRD however is meant to deal with many different kinds of PCS tools and purposes. One utility distinctive to PCS is service improve avoidance and feeder overload management, which evaluates a product’s skill to make sure feeder and repair conductors are usually not overloaded by load and/or supply management.
The event of the brand new UL 3141 customary will likely be necessary to offer tools producers and different stakeholders with confidence that PCS merchandise sooner or later will likely be evaluated for reliability and security as principal necessities for itemizing.
The second version of UL’s Define of Investigation for Energy Management Programs will likely be printed this yr, adopted by the formal, consensus UL 3141 customary in 2025 or early 2026. We encourage you to trace UL updates and submit public suggestions if you wish to be concerned within the drafting course of.
Conclusion
At a sure level, the widespread adoption of distributed power sources turns into an optimization downside that’s solvable with energy management programs. Whether or not a enterprise proprietor needs to impress operations with out a main service improve or a public utility hopes to keep away from pricey transmission upgrades by controlling hundreds of small, grid-tied masses and sources, electrical programs of all scales have gotten smarter and safer by integrating PCS. As these revolutionary applied sciences evolve, anticipate codes and requirements to observe swimsuit.
Be taught extra about UL 3141 on the Mayfield Renewables Schooling Summit in Austin, Texas. Click on right here for occasion particulars and registration.
