Standard for Safety for Power Control Systems

Note: The scope for this NOI (originally published on January 16, 2024) was updated by the responsible SDO on November 26, 2024.

1.1 These requirements cover Power Control Systems (PCS) used in Distributed Energy Resource (DER) systems which include one or more power sources in addition to the primary power source, typically the utility grid. The PCS electronically limits or controls current or power to stay within defined limits and may consist of a single device or multiple devices operating together as a system. The current or power measurement reference point(s) may be located internally to equipment or externally within the system. All elements of the PCS are intended to be installed in accordance with the National Electric Code (NEC). Section 705.13 in the 2020 edition or Section 750.30 in the 2023 edition or the Canadian Electrical Code, Part I Safety Standard for Electrical Installations, CSA C22.1.

1.2 PCS may be evaluated and rated for one or more of the primary types of PCS addressed in 1.3 – 1.5 as well as provide one or more of the PCS functions in accordance with 8.1.1 of this Standard. See 10.1 for details regarding rating requirement specifics.

1.3 A PCS may be evaluated as a single source PCS. Single source PCS provide an overload functionality when used with a passive protective device [e.g. Overcurrent Protective Device (OCPD)] used for the protection of service, feeder, or branch circuits. A single source PCS limits power drawn from a single source of supply [e.g. the area Electric Power System (EPS)] via load management.

NOTE 1: Uncontrolled sources complying with the requirements of NEC 705.12 may be present in a single source PCS however these sources are not controlled by the PCS. A single source PCS often provides overload control for power imported from the area EPS through load management.

NOTE 2: A single source PCS is located in a circuit(s) where branch circuit rated OCPD’s located external to the PCS provide additional protection from overloads.

1.4 A PCS may be evaluated as a multisource PCS. Multisource PCS contain critical overload functionality addressing system overload conditions of systems supplied by more than one source and have control over more than one source. Multisource PCS may contain separate passive protective devices included in their design however these passive protective devices are unable to fully address overload conditions of the multisource system in the event the PCS fails.

NOTE: Multisource PCS may include passive protective devices (typically overcurrent protective devices (OCPDs) used for the protection of service, feeder, or branch circuits however the PCS controlled conductors are able to experience overload conditions that the passive protective devices are not able to fully address at the system level. The PCS functionality addresses these system overload conditions of the PCS controlled conductors in accordance with NEC 705.13.

1.5 A PCS may be evaluated for power import limiting (PIL) and/or power export limiting (PEL) functionality where the PCS control and monitoring point is at an external reference point of applicability, such as the point of common coupling with the area EPS. The PCS may limit current and/or power flow from generation sources to the Area EPS (exporting) or limit current and power flow from the Area EPS to loads / the local EPS (importing). PEL and PIL functions do not address overload mitigation in accordance with 8.1.1, items (b) – (e) (overload conditions as defined in the NEC or for installations in Canada in the Canadian Electrical Code, C22.1).

NOTE: PIL / PEL functions only address utility facing functionality (area EPS side of the PCC) and do not address NEC overload conditions (local EPS side of the PCC). PCS may be evaluated only for PIL/PEL functionality, NEC overload functionality, or a combination of both functionalities. The ratings of the PCS reflect which functionalities are included in the scope of the evaluation of the PCS.

1.6 In addition to the required autonomous operation, the PCS may respond to external commands or schedules provided by authorized third parties. The format for scheduling of export or import to or from utilities is defined in this Standard, but specific communication protocols, or other methods, used for transmitting commands or schedules are outside the scope of this Standard. See Annex A for further details.

1.7 The requirements in this Standard are intended to evaluate PCS that electronically control power or current flow within local EPS power distribution equipment, or import or exported to the area EPS, via use of external measurement and control devices. Such systems may be made up of generation devices (inverters, engine generators, etc.), energy storage systems, loads, load control applications ((charging power/load management, etc.), circuit controllers, or other equipment used to manage the current or power flow at the point of reference. The power control function may utilize communication-based approaches and may include onsite monitoring devices and or controllers remote from the point of control.

1.8 The PCS may include multiple external reference points used to control power or current on multiple conductors or bus bars. For example, an external point of reference may be at the Point of Common Coupling (PCC) to control power flows to or from the utility grid as well as providing overload protection of the busbars in the main service panel. External reference points may also be located to control currents within a piece of equipment or on other circuits on the premises wiring.

1.9 Products and systems covered by this Standard are intended to be installed in accordance with the National Electrical Code, NFPA 70, and the Canadian Electrical Code, Part I Safety Standard for Electrical Installations, CSA C22.1.