Final Thoughts

For many people IEC 61850 sampled values may look like emerging technology. But that is not the case. They have been around for a while.

With electromechanical and solid state relays we simply had no choice. We needed and electric signal to drive the electromechanical device or the electronic circuits.

And that was the output of the current and voltage transformers - secondary currents and voltages. However, with the invention of optical current sensors things started to change. The benefits of these sensors were significant, but they required an interface with the protection relays.

Converting the primary current into an optical signal and then to a low level analog signal that then needs to be converted to digital data to be processed in the IED was too cumbersome, with each transformation introducing additional errors and taking some time.

The international standard IEC 60044 Instrument transformers – Part 8: Electronic current transformers was published in 2002, introducing the concept of the Merging Unit. This idea was incorporated then by IEC TC 57 Working Group 12 in IEC 61850

Part 9-1: Specific communication system mappings (SCSM) - Serial unidirectional multidrop point-to-point link and

Part 9-2: Specific Communication Service Mapping (SCSM) -Sampled values over ISO/IEC 8802-3 (2004)

In order to ensure interoperability between merging units and multifunctional IEDs, the UCA International Users Group published also in 2004 the Implementation guideline for digital interface to instrument transformers using IEC 61850-9-2.

To prove that the technology works, several major suppliers participated in an interoperability demonstration at the 2004 CIGRE Session in Paris, giving the start of the implementation of IEC 61850 based applications at pilot projects around the world. So, as you can see, sampled values have been around for 10 years. It is not new! And you can buy merging units and multifunctional IEDs or disturbance recorders based on the technology from several manufacturers.

The benefits of the technology are significant, so if you have not done it yet, get some and try it.

BeijingSifang June 2016