Future of phasor measurement systems

Phasor measurement is an impressive technique of estimating the phasor equivalent of an AC waveform.  Advances in computing using inexpensive microprocessors and microsecond time dissemination through the GPS system have made this breakthrough possible.  Still, these are just measurements of power system quantities and not an end in themselves.  They provide value through the analysis, monitoring, and controls that can be done with them.  They are a building block for new generations of applications which need developers knowledgeable in the measurement and the advantages it provides.
Most of the emphasis in phasor measurements has been the high bandwidth, low noise aspect that makes dynamic analysis and clear visualization possible.  This is certainly where the technique shines in comparison with current methods.  However this measurement can be used in many ways with different types of applications.  Lower speed SCADA situational measurements for operator reporting and alarms can use phasor data.  State estimation is an ideal application for phasor measurement, since phasors are the actual measurement of what could previously only be estimated.  Phasor based controls take advantage of high speed, low latency as well as accuracy.  We have demonstrated successful PMU deployments and have built high-speed, centralized systems and have proven that they work.  We have shown some of the measurement capability and their advantages.  We now need more focus on the applications.  We need to adapt and tailor the measurement system to meet those needs, rather than build one type of measurement system that applications must adapt to.
The high bandwidth systems being built today with relatively few measurements fill the need for many applications like disturbance monitoring and situational awareness.  But SCADA reporting and state estimation needs many points, preferably every bus on the grid.  Scaling a high speed data system to that size is very difficult and expensive to implement, and more difficult to maintain.  In addition, the extensive communication systems and protocols used in an EMS do not adapt well to the high speed phasor systems.  Eventually SCADA type reporting systems will speed up, so that high-speed phasor type systems may become the SCADA of tomorrow.  In the meantime, lower speed reporting that includes precise measurement timing with anti-aliasing protection is needed.  For example, if phasors were reported on the even second (ie, every 2 seconds) to the SCADA master, the measurements could be combined  accurately for precise angle determination.  The next generation PMUs (or PMU functions in other devices) should be able to report to several applications using different protocols and data rates.
There is no need to restrict phasor measurements to a single protocol system.  The very successful IEEE standard C37.118-2005 prescribes a specific protocol for real-time data transfer, but doesn't prohibit the use of any others.  This standard has been a big help to the industry by specifying a simple protocol that is easy to implement and makes a device interoperable among vendors.  The basic methodology can be adapted to other protocols, such as ICCP, DNP-3 and IEC61850 to create compatible data transfer within those protocols.  Wider adaptation will make these measurements available to more applications and spread the benefit.
Even in the area of high-speed data systems there are differing requirements.  Precision modal analysis needs careful filtering to remove aliased artifacts.  Filtering causes delay, and controls are very sensitive to delay.  Continuous feedback controls need careful filtering and bandwidth limitation to prevent instability.  Feed-forward (bang-bang) controls are usually insensitive to small signal events except when they become unstable, so only require minimal filtering. The end application is always the deciding factor in specifying the measurement requirements.
So do we need to abandon the measurement systems we have been building in favor of other approaches?  Not a bit.  Great strides are being made in PMU testing.  This has shown that the current PMUs in production make very similar measurements that can be widely used.  Most data systems currently being deployed are nowhere near hardware and software capacity.  As shown above, adapters are being created to effectively convert data between applications.  In the short term of 5-10 years, the systems being deployed will serve their intended functions, including many applications.  However as new applications are developed, we should expect to encounter differences that will require broadening the measurement and data reporting systems.