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Details needed about OpenPDC

Sep 23, 2010 at 7:39 AM


1.Can I get what is purpose of attaching ID to the incoming measurements and how is it done. Since the data frames will be from multiple PMU how can this be done? What ID is it?

2.Is the sorting done before combining the frames ?

3. How then do u combine the frames from multiple PMU as they may contain variable data. How the field separation is done?


Plz help if any one could....

Sep 23, 2010 at 1:02 PM

The openPDC is a measurement based concentration system - this means that the system disassembles data frames into measurements before processing. Because of this, each measurements gets assigned a unique ID for processing. When you add a device to the system it automatically defines a set of signals for the device along with this unique ID.

During concentration (i.e., "sorting"), the measurements are aligned according to their source timestamp - at this point it is the individual measurements, not the original data frames, that are being sorted - at this stage there is no longer a concept of a data frame as you have left the "phasor processing world" and entered the "measurement processing world".

To produce an ouput stream the system takes sorted measurements (from any source, calculated, from phasor devices, etc) and reconsitutes them into a familiar phasor data frame.

By reducing all inputs into measurements the system becomes a more powerful real-time signal based processing system instead of a simple phasor data concentrator as the system can (1) be extended to parse inputs from any source, (2) can process all measurements from all sources in a similar fashion, and (3) since everything is available in the system as a measurement, data can be archived to any historian.

Hope that helps to clarify a little.


Sep 23, 2010 at 3:07 PM

Thanks Ritchie


But I still have certain doubts..

I went through the IEEE37.118 std. I was trying to develope a mini PDC in C language  for academic purpose. I am not getting how each PMU's configuarion frame is to be dealt.

Whether i need to store it in database and later when the data frames corresponding to that PMU arrives i have to separate the  different measurements  from the data frames by comparing with configuration frames. If it is so how do I separate the measurements as it would take a lot of time when extracting the measurements from data frames by comparing with the conf. frames.

And as the data frames and configuration frames are going to increase in size as you go upwards in the hierarchy from PDC to PDC ,how to deal with that..


In the reply which you have given each measurements gets assigned a unique ID for processing does it mean the measurements that come inside a data frame, and what ID do you assign. Is it a user defined lD or a PMU/PDC ID.

Since the data frames from multiple PMU's will be coming at very fast rate when to sort the measurements in these frames. Do we need to buffer id assigned measurements and then sort.

Lastly when we combine the measurements we also need to build a configuration frame to be passed on to higher level PDC. How do we do that. As there PDC to PDC number and type of measurements may vary.

Kindly clarify me on these doubts as I need them urgently...






Sep 23, 2010 at 4:25 PM

Maybe I am confused on what you are trying to accomplish, I was explaining what the openPDC currently does in order to accomplish its tasks. If you are trying to write your own PDC, you may not need to go to that level of detail - you can just sort frames.

To reiterate, the openPDC follows these steps:

1) Parse IEEE C37.118 Data Frame

2) Map individual channel values to measurements using preconfigured permantly assigned ID's (assigned from a parse of the IEEE C37.118 Configuration Frame)

3) Send the mapped measurements along to other processes

4) One of the processes is a concentrator which sorts measurements by time

5) Concentrator then takes sorted measurements and produces a combined IEEE C37.118 Data Frame assigning channel values

6) New frame is published...


Sep 23, 2010 at 6:25 PM

Hi Ritchie,


Thanks for Reply. This  info will certainly help me. Will get back to you if any further query......


With BRegards


Sep 29, 2010 at 2:49 PM

Hi Ritchie


1.I have created a data structure that separates the incoming configuration frames. For the incoming data frames i will have to match the fields from data frames

to the one in cnf frame data structure in order to separate the measurements. If suppose some PMU data frames for a particular time frame do not arrive then how do i combine the frames. To how much time should i wait as i focus to make the system more as a real time.(Considering I maintain a buffer.If you have any good suggestion most welcome)

2.For the data frames, I need to create a data structure. How the sorting of these data structure nodes be done. Will it be done after some set of data nodes have been collected and then apply the timestamp based sorting algorithm.


WIth BRegards