Final Thoughts

With the development and deployment of PMUs in significant numbers, there is an increasing need for increase of their applications.

The introduction of the P class of synchrophasor measurements makes it possible to consider the development and implementation of protection schemes based on such measurements. The extensions of IEC 61850 to cover applications outside of the substation, the increased interest in IEC 61850 sampled values based substation protection, automation and control systems and the acceptance of IEEE C37.238 as the precision time protocol for the electric power industry create an environment in which it makes a lot of sense to start using synchrophasors for protection.

The fact that the PMUs are accurately time synchronized makes it possible to use synchrophasor measurements for transmission line differential, as well as bus differential protection. However, in order to do that, we need to understand the response of the P-class PMUs to the fast transients that occur during short circuit faults, the response of the conventional and unconventional instrument transformers or sensors, the filtering methods that are used, the latency of the communications interface, the impact of the loss or time synchronization or GPS spoofing and many others.

We will have to overcome some challenges in order to achieve interoperability between PMUs and protection IEDs not only from communications point of view, but also from performance point of view. This does not mean that we should wait. The benefits that we will get from PAC systems based on sampled values and synchrophasors are too big to be ignored.

To answer the question in the title – Yes, we can use synchrophasors for protection.

But we need to understand and overcome the difficulties and properly test the performance of all components of the protection schemes based on their use.


BeijingSifang June 2016