Energy Management (EMAN) Applicability Statement
Extracted elements (25)
AC Power Quality measurements were reused from IEC 61850-7-4, and Accuracy Classes for power/energy measurement were adapted from ANSI C12.20 and IEC 62053-21/62053-22, rather than defining new measurement semantics, to align EMAN with established utility standards.
EMAN addresses IP-enabled networks through SNMP MIBs, deliberately not targeting ZigBee-style low-power mesh networks. ZigBee provides inexpensive self-organizing mesh solutions for embedded sensing and home automation where SNMP would be inappropriate.
EMAN deliberately excludes Smart Grid coordination, electricity production, and distribution from its scope. It can support demand response only indirectly by allowing an EnMS to translate a signal from an outside grid entity into device-level control actions.
EMAN does not create a new protocol stack; instead it defines a data and information model for measuring and reporting energy over SNMP. This leverages SNMP's existing, industry-proven discovery, security, and device-control mechanisms across a large range of devices.
Printers require event- or notification-based reporting rather than periodic polling alone, because power consumption spikes sharply and briefly during active printing while being very low in timer-based low-power states; periodic polling would miss these transient peaks.
EMAN references the DMTF Power State Management Profile (DSP1027) and Power State Set for power-state control. The DMTF standard covers power-state control (sleep, hibernate, off) but does not include energy monitoring, which EMAN provides.
The ANSI/CEA-2047 standard provides a device-identification, current-power-level, and cumulative-energy-consumption information model for home appliances across Wi-Fi, Ethernet, ZigBee, Z-Wave, and Bluetooth. It is intended as a base model for other groups to build protocol-specific implementations, overlapping with EMAN's scope for residential devices.
The data center UPS MIB can monitor battery capacity, input load, and output load of UPS devices, but there is currently no defined link between the UPS MIB and the ENTITY-MIB, leaving a gap in hierarchical containment modeling for UPS units.
The Ecma Smart Data Centre standard (ECMA-400) defines four power states (Off, Sleep, Idle, Active) and a protocol-agnostic semantic model across SNMP, BACnet, and HTTP. When used with EMAN, SDC provides a thin abstraction on top of EMAN's more detailed data model.
The PWG Power Management Model for Imaging Systems (PWG5106.4) and its companion SNMP MIB (PWG5106.5) are harmonized with DMTF CIM for power states; the EMAN framework takes these into account and the PWG may harmonize its MIBs with EMAN MIBs.
When a PD (e.g., PoE IP phone) supports EMAN, two power usage reporting mechanisms coexist: one performed by the PD itself and one performed by the supplying PSE. Device-specific implementations must determine which reporting source to use.
Power monitoring and management MIBs may have privacy implications, as noted in RFC 7460 Section 10 and RFC 7461 Section 6. Additional privacy considerations may arise for each specific use case (e.g., occupancy inference from building energy data), but these are not analyzed in this applicability statement.
A mid-level manager is a device (commonly a switch or proxy) that aggregates energy data reported by associated devices and forwards the aggregated data to an EnMS or a higher mid-level manager, irrespective of whether it powers those devices.
An Energy Management System (EnMS) is an NMS that collects energy information for devices in the network; it may be limited to monitoring or may also implement control functions. It differs from a general NMS in that it deals exclusively with energy.
Demand response is a use case where EMAN power states enable an EnMS to reduce network energy consumption in response to time-of-day price fluctuations or grid shortages, by selectively shutting down lower-priority devices or uniformly reducing power to a device class.
Energy object relationships include a powered-by relationship (indicating power source) and a metered-by relationship (indicating which device meters another's consumption). These relationships are modeled explicitly in the EMAN information model.
Energy objects that support the EMAN framework possess their own Universally Unique Identifier (UUID) and are responsible for their own power reporting and control. Devices without EMAN capabilities rely on their supplying device (PSE) for power reporting.
Energy storage devices (batteries, hydrogen cells) are modeled as components contained within a device from an ENTITY-MIB perspective. The Battery MIB (RFC 7577) provides reporting for actual charge, age, and battery state.
Four abstract use case patterns are defined for energy objects: (1) Metering only, (2) Metering and Control without power supply, (3) Power Supply with Metering and Control, and (4) Multiple Power Sources with varied metering and control assignments.
Non-residential building system gateways perform protocol conversion between IP/EMAN and legacy building automation protocols (BACnet, Modbus, ZigBee) via RS-232/RS-485 or Ethernet interfaces, collecting energy usage from HVAC, lighting, and other building systems.
Power Sourcing Equipment (PSE) devices (e.g., PoE switches) supply power to Powered Devices (PDs) over Ethernet or USB per RFC 3621. The PSE can control per-port power supply and meter actual power provided, and can associate each port with a specific connected device.
The EMAN framework defines an information model for electrical equipment covering four areas: energy object identification, energy object context, power measurement, and power characteristics. SNMP MIB modules are specified based on this model, though other mechanisms such as YANG/NETCONF are equally applicable.
The ENTITY-MIB (RFC 6933) containment model is used to uniquely identify physical subcomponents of network devices. The entPhysicalContainsTable with entPhysicalChildIndex and the entPhysicalContainedIn object express parent-child energy object containment (e.g., line-card within chassis).
Three types of energy measurement are defined: energy input to a device, energy supplied by a device to other devices, and net (resultant) energy consumed (the difference between input and supplied). This distinction is required because energy objects may both consume and provide energy.
EMAN inherits its security capabilities from SNMPv3 (RFC 3411), which provides confidentiality, integrity, and authentication for all EMAN-related MIB communications. No additional EMAN-specific security mechanisms are defined.