How to Model Thousands of Measurement Signals?

The standard series IEC 61850 was originally developed for high voltage substation automation and protection ... with well defined logical nodes and data objects representing the most crucial signals like status (CSWI.stVal), 3-phase electrical measurements (MMXU.V.phsA ...), temperature supervision (STMP.Tmp, STMP.Alm, ...) and many other signals.
Several applications require huge number of values, e.g.,

1. Logs (hundreds of status changes over a long period)
2. Power Quality measurements (hundreds of values of min, max, ...)
3. Temperature (hundreds or thousands of raw measured or processed values)

The corresponding logical nodes and communication service models would end-up in a lot of overhead in the modelling or in the communication.
I have discussed the first two bullets already inside the standardization groups ... more details may be discussed in a future blog post.
Today, I will discuss the third issue: huge amount of temperature values.
First of all, there are two models for temperature: TTMP (Transducer for a single sensor value) and STMP (Supervision of a single temperature value) with the following excerpt of details:

TTMP.TmpSv.instMag and TTMP.TmpSv.q are the two mandatory data attributes.

STMP.Tmp.mag.f, STMP.Tmp.mag.q, STMP.Tmp.mag.t (Tmp is optional)

STMP.Alm.stVal, STMP.Alm.q, STMP.Alm.t (Alm is optional)

STMP.Trip.stVal, STMP.Trip.q, STMP.Trip.t (Trip is optional)

Second, If you want to communicate just hundreds of temperature values, I would model this application as follows (SIUnits and sample rate ... may be modeled as well):

[Sure, I am aware that multiple instances of TmpSv are not yet standardized ... I would not care a lot at the moment ... it will come anyway. If not, define an extended Data Object TmpSamp with multiplicity 0..*]

TTMP1.

TmpSv1.instMag and TmpSv1.q
TmpSv2.instMag and TmpSv2.q
TmpSv3.instMag and TmpSv3.q
...
TmpSv100.instMag and TmpSv100.q

DataSet="DsTTMP1"

FCDA=TmpSv1.instMag
FCDA=TmpSv2.instMag
FCDA=TmpSv3.instMag
...
FCDA=TmpSv100.instMag

Unbuffered Report CB="UnbTTMP1

Data Set="DsTTMP1" 
trigger option: integrity period 
period: 1 h or ...

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

TTMP2.

TmpSv1.instMag and TmpSv1.q
TmpSv2.instMag and TmpSv2.q
TmpSv3.instMag and TmpSv3.q
...
TmpSv100.instMag and TmpSv100.q

DataSet="DsTTMP2"

FCDA=TmpSv1.instMag
FCDA=TmpSv2.instMag
FCDA=TmpSv3.instMag
...
FCDA=TmpSv100.instMag

Unbuffered Report CB="UnbTTMP2

Data Set="DsTTMP2" 
trigger option: integrity period 
period: 1 h or ...

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

TTMP3.

TmpSv1.instMag and TmpSv1.q
TmpSv2.instMag and TmpSv2.q
TmpSv3.instMag and TmpSv3.q
...
TmpSv100.instMag and TmpSv100.q

DataSet="DsTTMP3"

FCDA=TmpSv1.instMag
FCDA=TmpSv2.instMag
FCDA=TmpSv3.instMag
...
FCDA=TmpSv100.instMag

Unbuffered Report CB="UnbTTMP3

Data Set="DsTTMP3" 
trigger option: integrity period 
period: 1 h or ...

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

Third, If you want to use hundreds of temperature values AND alarms AND trips etc. then STMP would be the right choice. The above modeling approach would be the same.
In addition to the data sets for the measured values, you may also configure data sets for the quality "q", and configure report control blocks with trigger option "data change". You may also add the quality into the other FCDAs ... depending on how crucial the quality is for the client application.

How to define New Data Objects in IEC 61850?

The need to define new data objects is likely to have various reasons. One reason is that experts do not know which logical nodes and data objects are already defined. Let’s assume there is really a need for a new data object – there is not any data object that may fit.

Example (The following LN SIML, I found on the Web):

The standard LN SIML (Insulation Medium Supervision) provides the data object H2ppm (Measurement of Hydrogen (H2 in parts Per Million)):

There is a need to model H2ppm related semantic, e.g., “Hydrogen ppm Rate of Change” or “Hydrogen ppm Rate of Change Goodness of Fit”

These two semantic models are not defined in the standard. What is the best way to model these two?

1. Defining values in GGIO? – maybe not,
2. Defining new data objects in SIML? – may be the best solution (could be standardized later), or
3. Defining something like H2ppm1 (measured value), H2ppm2 (rate of change”, and H2ppm3 (roc Godness of Fit)? – That is definitely wrong!

Why are the following data objects in conflict with the standard modeling method?

Here is the definition for LN SIML (of the example I found) using multiple instances of H2ppm, defined in the Insulation Medium Supervision (Product Specification):

The standard IEC 61850-7-4 Edition 2 defines the LN as follows:

LN: SIML Name: Insulation Medium Supervision (Standard IEC 61850-7-4 Edition 2):

These data objects H2ppm1, H2ppm2, and H2ppm3 are not allowed – it is not allowed to instantiate data objects (with some exceptions, then the data object in the standard LN needs to be defined as MyDataObject1 – with a “1” at the end)!

For details on instantiating data objects see the following excerpt of IEC 61850-7-1 Edition 2 that defines the extension rule for data objects:

14.6 Specialisation of data by use of number extensions

Standardised data names in logical nodes provide a unique identification. If the same data (i.e. data with the same semantics) are needed several times as defined, additional data with number extensions shall be used. The rules for number extensions shall follow the naming conventions defined in IEC 61850-7-2 and be as follows:

• the number extension usage shall only be defined by the owner of the data namespace. This shall be done by adding the number extension 1 to a data object name (e.g. data1),
• data with no number extension shall not be extended by third parties,
• data with the number extension 1 can be extended. Number extensions may be ordered or not (1,2,3,4, or, 1,2,19,25),
• if only one instance of an extendable data is present in an LN, it shall have the number extension “1”.

14.8 Example for new Data

New Data “Colour of Transformer Oil”

The above figure shows also that a data Namespace Attribute “datNs” has to be specified for each new data object.

For the above listed additional semantic it would work with the following (standard conformant) extended data object definitions:

Example (wrong – semantic is in instances):
H2ppm1 (measured value)
H2ppm2 (rate of change)
H2ppm3 (roc Godness of Fit)

A standard conformant solution is (define new data object classes):
H2ppm (measured value)
H2ppmRoc (rate of change, extended data with datNs=Vendor so and so )
H2ppmRocGdns (roc Godness of Fit, extended data with datNs=Vendor so and so)

Please find further presentations on model extensions:
Click HERE for post1.
Click HERE for post2.