IEC 61850-90-5

Specifies the use of IP multicast (UDP/IP) to efficiently stream synchrophasor data from a single publisher to multiple subscribers across routed wide-area networks. This replaces the point-to-point serial connections of legacy protocols, allowing a single PMU stream to be consumed simultaneously by a local PDC, a regional control center, and a backup data center without duplicating bandwidth. The standard defines the mapping of IEEE C37.118.2 data frames directly into UDP payloads, preserving the existing synchrophasor frame structure while enabling network-layer routing.

Mandates the use of the Group Domain of Interpretation (GDOI) protocol (IETF RFC 6407) for secure key management and session establishment. This framework provides:

• Authentication: Verifying the identity of publishers and subscribers before data exchange.
• Encryption: Protecting synchrophasor data confidentiality over untrusted WAN links using symmetric keys.
• Integrity: Ensuring data frames are not tampered with in transit. The standard leverages a centralized Key Distribution Center (KDC) to manage security associations for all participating devices in a multicast group.

Utilizes the Session Description Protocol (SDP) (IETF RFC 4566) to formally describe the characteristics of a synchrophasor data stream before transmission begins. An SDP file, distributed out-of-band or via a well-known server, contains critical metadata including:

• Multicast group address and destination port.
• Payload type and encoding format (e.g., IEEE C37.118.2 frame).
• Session name, information, and timing parameters. This allows subscriber applications to automatically configure their network interfaces and parsers without manual intervention, enabling plug-and-play interoperability.

Provides a standardized mechanism to tunnel IEEE C37.118.2 frames over the IEC 61850-90-5 transport profile. This design choice preserves the significant investment in existing PMU hardware and PDC software that already generate and consume C37.118.2 data. The standard does not redefine the synchrophasor measurement payload itself; instead, it wraps the legacy frame inside a secure, routable envelope. This pragmatic approach decouples the communication infrastructure upgrade from the measurement device lifecycle, allowing utilities to modernize their WAN transport without replacing field equipment.

Defines the use of Differentiated Services Code Point (DSCP) markings on IP packets carrying synchrophasor data. By tagging real-time measurement streams with a high-priority DSCP value (typically Expedited Forwarding, EF), the standard ensures that routers and switches across the utility WAN prioritize synchrophasor traffic over lower-priority background data. This is critical for maintaining the deterministic, low-latency delivery required by wide-area control and protection schemes, where a delayed measurement is functionally equivalent to a lost measurement.

Supports the transmission of identical synchrophasor streams over physically diverse network paths using separate multicast groups. A subscribing PDC or application can receive two copies of the same data stream and select the valid one based on sequence numbers and timestamps. This architecture provides hitless failover in the event of a fiber cut or router failure, meeting the high-availability requirements of System Integrity Protection Schemes (SIPS). The standard's use of standard IP routing protocols (OSPF, BGP) allows the network itself to automatically reconverge around failures.

A node that aggregates, time-aligns, and processes streaming synchrophasor data from multiple PMUs. The PDC receives IEC 61850-90-5 multicast streams, correlates frames by GPS timestamp, and outputs a coherent system-wide dataset.

• Performs data alignment to create simultaneous snapshots
• Handles missing or late frames with configurable wait times
• Feeds higher-level applications like state estimators and oscillation detectors

The foundational standard defining synchrophasor measurement accuracy, data formatting, and real-time communication. IEC 61850-90-5 complements rather than replaces C37.118 by adding routable IP transport to the existing measurement framework.

• C37.118.1: Measurement compliance and Total Vector Error (TVE) limits
• C37.118.2: Legacy TCP/UDP data framing (non-routable)
• 90-5 wraps C37.118 payloads in routable IP multicast packets

A network protocol defined by IEEE 1588 that synchronizes clocks throughout a computer network, achieving sub-microsecond accuracy. PTP provides the time reference for synchrophasor measurement in substations where GPS antenna installation is impractical.

• Achieves < 1 microsecond synchronization over Ethernet
• Uses a master-slave hierarchy with transparent clocks
• Essential for IEC 61850-90-5 deployments in GPS-denied environments

An integrated system that uses real-time synchrophasor data to enhance grid situational awareness and automatically execute corrective actions. IEC 61850-90-5 is the communication backbone that makes WAMPAC possible across large geographical regions.

• Enables sub-synchronous oscillation detection across interconnections
• Supports closed-loop Wide-Area Damping Control (WADC)
• Triggers System Integrity Protection Schemes (SIPS) for blackout prevention

A hardware device that combines a stable local oscillator with a GPS signal to provide an ultra-precise time and frequency reference for PMU sampling. The GPSDO ensures the timestamp accuracy required for meaningful wide-area phase angle comparisons.

• Maintains holdover stability during GPS signal loss
• Provides 1 PPS (pulse per second) and IRIG-B time codes
• Critical for achieving the < 1 microsecond timing accuracy required by synchrophasor applications