Phasor Measurement Unit (PMU)

A time-synchronized measurement of voltage and current magnitude and phase angle, calculated by a PMU. The measurement is tagged with a precise UTC timestamp from GPS, allowing direct comparison of phase angles across widely separated locations. Standardized by IEEE C37.118, synchrophasors provide the foundational data unit for wide-area visibility, enabling detection of inter-area oscillations, voltage instability, and frequency deviations that traditional SCADA polling cannot capture.

A centralized device or software function that aggregates, time-aligns, and correlates synchrophasor data streams from multiple PMUs across a wide area. The PDC buffers incoming frames, waits for data with matching timestamps, and outputs a single synchronized data stream to higher-level applications. It also performs latency monitoring, data quality checks, and protocol translation between IEEE C37.118 and IEC 61850-90-5 for integration with substation automation systems.

An integrated software platform that ingests real-time synchrophasor data from PDCs to provide visualization, alarming, and post-event analysis of large-scale grid dynamics. Core functions include:

• Mode meter: Identifies poorly-damped inter-area oscillations
• Phase angle monitoring: Detects stress across transmission corridors
• Frequency monitoring: Tracks propagation of frequency disturbances WAMS complements traditional SCADA by revealing dynamic phenomena invisible to 2-4 second polling.

The defining standard for synchrophasor measurement, data transfer, and performance. It specifies:

• Measurement classes: P-class (fast response for protection) and M-class (high accuracy for monitoring)
• Total vector error (TVE): The key accuracy metric, combining magnitude and phase errors
• Communication framing: Binary and command frames for real-time streaming The standard ensures interoperability between PMUs from different vendors and defines compliance testing procedures.

An automated protection system that uses PMU inputs to detect predefined grid stress conditions and execute pre-planned corrective actions within milliseconds. Also called Special Protection Scheme (SPS). Typical actions include:

• Generator tripping or runback
• Load shedding
• Controlled islanding PMU-based RAS provides faster, more selective response than traditional relay-based schemes by using wide-area phase angle comparisons to detect instability before local relays would operate.

An extension to the IEC 61850 standard that defines how to transport synchrophasor data over routable networks using IP multicast. It maps IEEE C37.118 synchrophasor frames into IEC 61850 Sampled Value (SV) or GOOSE message structures, enabling seamless integration of PMU data into the substation process bus. Key features include IEEE C37.118.2 compatibility, session management, and security provisions from IEC 62351 for authenticated and encrypted wide-area synchrophasor streaming.