by Alex Apostolov, Editor-in-Chief

Estimation or Observation

Synchrophasors were invented in 1983 and have been around since the early 1990s.

I remember when we installed a synchrophasors measurement unit at New York State Electric and Gas in 1993 as part of a New York State project to gain some experience and see what we can do with this technology. So, it has been more than a quarter of a century of synchrophasors availability and things have changed a lot, while at the same time in many places staying very much the same.

What has changed is actually many things:

  • Phasor Measurement Units (PMUs) are not exotic single function devices anymore. PMU is not neces-sarily a dedicated device anymore, but a measuring function in most of the multifunctional protection and control intelligent electronic devices (IEDs) 
  • The synchrophasor measurements have evolved as well. While at the beginning there was a single standard - IEEE C37.118 defining both synchrophasors and how they are communicated, in 2011, as a result of decisions to harmonize IEEE and IEC standards development, the original standard was split in two standards: C37.118.1-2011 - IEEE Standard for Synchrophasor Measurements for Power Systems and C37.118.2-2011 - IEEE Standard for Synchrophasor Data Transfer for Power Systems
  • Initially the PMUs from different manufacturers were publishing only synchrophasors calculated by vendor specific algorithms using data from several cycles and suitable for only steady state power system conditions. Today IEEE C37.118.1 defines two classes of synchrophasors - P and M. The P class is intended for protection types of applications requiring fast response and does not require explicit filtering.  M class is intended for applications which could be adversely affected by aliased signals but do not require the fastest reporting speed
  • Time synchronization of devices calculating synchrophasors today is based on the Precision Time Protocol (PTP) and its utility profiles
  • IEC 61850 now also supports synchrophasor communications using the sampled values communication services

As a result of all these changes today we are seeing a transition in the applications of synchrophasor measurements. While at the beginning a limited number of strategically located PMUs were providing measurements intended to support and improve steady-state estimation at the SCADA level, today the synchrophasor measurements available in thousands of multifunctional protection and control IEDs allow us to transition from estimation to observation.

The articles in this issue of the magazine demonstrate the significant progress that our industry has made. Initially Wide Area Monitoring Systems (WAMS) were developed to support the system operator with some forms of situational awareness and visualization tools. Today the focus is shifting to Wide Area Monitoring, Protection, Automation and Control Systems (WAMPACS) that allow the development and implementation of automated solutions for detecting and mitigating wide area disturbances based on P-class synchrophasor measurements and routable GOOSE messages.
By observing both the steady-state and dynamic state of the electric power grid now it becomes possible to perform dynamic state estimation for the impact of system events, such as short circuit faults on critical transmission lines or loss of generation and prepare for optimal response in case that such event occurs.
Another important benefit of the continuous electric power grid observation by WAMPACS is the ability to better understand the dynamics of the changing system driven by the increasing availability of renewable distributed energy resources with inverter-based interfaces. This will help us to observe things that we have never seen before and figure out ways to deal with them, so we can maintain the reliable and secure operation of the modern electric power systems.


"The world is full of obvious things which nobody
by any chance ever observes."

Arthur Conan Doyle

Power. Flexible. Easergy.
Let?s start with organization in protection testing