Sampled Values and IEC 61850-9-2 LE: What is it?

The other day I received the following email:

Dear Mr. Karlheinz Schwarz,
I am sorry to disturb you. My name is XXX and I am a researcher from YYY. I would like to ask some questions to you regarding the standard IEC 61850-9-2LE.

1) May I know the status of IEC 61850-9-2LE? Is the standard will be obsolete or remain as it this?

2) Can I get some explanations from you about the differences between IEC 61850-9-2, IEC 61850-9-2LE and IEC 61869-9?

I really appreciate your kindness and time to answer my questions above.
Thank you & best regards,

-------------------------------

I have a very good friend that I asked to answer for me. Her is his answer:

Dear Karlheinz, 

Sure I can do my best for that.

Thanks for this opportunity.

Dear XXX, please see my attempt to answer.

Your questions are our everyday’s questions, and my answers need to be taken with “common sense”, reasonability and not as law, where somebody is right and somebody is wrong.

This is the best I can say.

The IEC 61850-9-2 Light Edition (LE)  is NOT a standard.  It is an UCA profile; a sort of gentlemen agreement (followed by everybody so far), where in principle the dataset carried by the SV Message (Sampled Values message) is fixed to 4 voltages and 4 currents.

The sampling frequency is 80 samples per period (4000 Hz for 50 Hz systems and 4800 Hz for 60 Hz systems).

The length of the SV message is fixed (in terms of bytes)

The quality string has one “extra bit” (the 14th bit, for derived or measured of the analog quantity) compared with a “normal quality string” of IEC 61850 and also IEC 61869 series, of 13 bits.

The time synchronization is 1-PPS

There is formally no support for PTP time synch (typical of “Edition 2” of IEC 61850 standard. LE is “edition 1”)

There is formally no support for “SIMULATION” mechanism (typical od “Edition 2 “ of IEC 61850 standard; LE is “edition 1”)

And many others.

TO MY EXPERIENCE:

It is commonly understood (and you have to make sure it is commonly understood also by the people working in your projects: suppliers, consultants, utility engineers etc) that:

- 9-2 LE supports Simulation mechanisms

- 9-2 LE supports PTP as time synch (be careful that PTP is actually IEC 61850-9-3: 2016 )

Even if formally this is not strictly in line with the UCA specification for “LE”.

So, IEC 61850-9-2LE (written by UCA working group) is a profile of IEC 61850-9-2 (written by the IEC committee TC 57)

And today it is the only “standard” that is implemented and in service for process bus applications.

IEC 61869-9 (and also -6 and also soon the -13) are parts of the IEC 61869 series, written by the IEC committee TC 38 (Instrument Transformer). 

So they have to do with the Merging Units, they are also profiles somehow, and also many other requirements, that you need to fulfill if you want to have a Merging Unit according to IEC standards.

To my opinion, no matter what IEC 61850 says in general, if you do a Merging Unit and follow IEC, you should follow IEC 61869 series.

In principle, the IEC 6185069-9 standards are often associated to:

• “Dynamic” dataset. This means that not only 4 U and 4 I will be transmitted. I can transmit just  one voltage, or 25 currents, or 6 voltages and 3 currents.. This is done from SCL.
• Sampling frequency of 4800 Hz, no matter the power system frequency (50 Hz or 60 Hz).
• PTP time synchronization (for MU)
• 2 samples per SV message (so called ASDU). “LE” has only one sample per message (one ASDU per message)

But it is of course much more than that.

What about protection relays/protection functions?

TC 95 is responsible for protection functions in IEC.

In principle it  is TC 95 / MT 4 (Maintenance Team 4) that takes care of functional standards for protection functions (IEC 60255-121:2014 for distance protection for example). Other maintenance teams take care of protection related standards like EMC etc.

Recently TC 95 has started a new working group (WG 2) that considers IEC 61850 for protection applications. A Technical Report is on its way and parts of that technical report will be implemented in the so called IEC 60255-1xx series, for protection relays.

But this is not ready yet and all of this needs to be considered with extreme care and communication among all the involved parts in a project.

I work as well as consultant for IEC 61850 applications in relay protection. Mainly for TSOs, since many years. Please have a look at this paper, written by many of us active in TC 95 / WG2. I think it will help you to better understand.

https://www.researchgate.net/publication/334050781_Standardisation_Challenges_for_Digital_Inputs_and_Outputs_of_Protection_Functions_in_IEC_60255_series

If you are interested in what TC 95 / WG2 does, you are more than welcome to contact me and I’ll help you in joining “our” activities.

For your understanding, there is a high dialog between TC 95, TC 38 and TC 17 (circuit breakers) for making the use of IEC 61850 more interoperable not only at “data level” but also at “functional level”, at least for protection applications.

For metering or power quality applications, for example, I don’t know what to say.

I hope this helps you.

Karlheinz, your extra comments are always welcome.

My best regards

Andrea Bonetti

Just passed

 Fachtagung Schutz- und Leittechnik 2020 , Berlin, 18-19 February 2020

NEW FORMAT!  Megger Magazine: ELECTRICAL TESTER
White Paper - Testing ROCOF and IEC 60255-181 Standard

Article - IEC 61850 GOOSE interoperability
IEEE 2018- Paper on IEC 61850 substation maintenance
MATPOST 2019 Lyon FR – Paper on IEC 61850 and Automatic Fault Disturbance Analysis

First time in industry! long duration End to End testing without use of any computer!

Mr. Andrea Bonetti MSEE
Senior Application Specialist Relay Protection and IEC 61850
Active member of IEC TC 95 / MT 4 ”Measuring relays and protection equipment” since 2006.
Megger Sweden AB

andrea.bonetti@megger.com
Rinkebyvägen 19, SE-182 36 Danderyd (Stockholm)
Sweden