What is the fastest response I can obtain from PM8000 / ION9000 via Modbus TCP ?

[Benoit_Barbalat]

Hi community ! Apologies if this was already answered, but I couldn't find anything on the topic...

For some renewable projects, the integrators are asked to provide frequency and power parameters as fast as 10ms to a supervisor using Modbus TCP.

According to the ION Reference and ION Device Template Reference, this should be possible: Modbus slave modules are hybrid meaning if they are connected to a high speed power meter they should be refresh every half cycle (10ms in 50Hz).

However some customers seem to get erratic response times. Some under 10ms, but sometimes over 1s (happens every minute or so).

Questions :

1 - Can the comm card respond under 10ms ?

2 - Are the modbus registers updated every 10ms so that the information being returned is always up to date?

3 - If I poll my meter every 10ms, is there a risk to "overflow" the meter with requests? 

4 - Can trimming the fmwk help in eliminating longer response times and making sure the response times are consistently under 10ms?

5 - In general, is this feasible ? We advertise the PM8000 and ION9000 for renewables projects, this is critical for the operations of the wind/solar farms.

Thanks for your help!

Let me know if you have questions.

[Charles_Murison]

Hello @Benoit_Barbalat ,

To start the High End Platform meters (HEP) like PM8000, ION9000, ION74000 do not guaranty a specific response time. There is some data like x % of requests will respond in Y amount of time. If you need this data I recommend using technical support.

Please note that while the modbus slave module can be a high speed module, there are other components to modbus communication that may update once a second. Note that communication is a low priority task and if the meter is busy with other processes (like being a meter), the communications can be paused. There is also throttling that could cause a meter to stop responding for a period of time.

Questions :

1 - Can the comm card respond under 10ms ?
Depends on what else the meter is doing, cannot guaranty this time.

2 - Are the modbus registers updated every 10ms so that the information being returned is always up to date?
Unsure

3 - If I poll my meter every 10ms, is there a risk to "overflow" the meter with requests? 

Yes, depending on what other communication is on the network. The meter does have some self preservation (throttling) and may stop responding to messages

4 - Can trimming the fmwk help in eliminating longer response times and making sure the response times are consistently under 10ms?

Cannot guaranty a 10 ms response time regardless of what changes are made to the meter.

5 - In general, is this feasible ? We advertise the PM8000 and ION9000 for renewables projects, this is critical for the operations of the wind/solar farms.

@DanL are you able to speak to this question and question 2?

Regrads,

Charles

[DanL]

2. Yes, some modbus registers do update every half cycle (10ms)

5. I believe @Sanjeet_Sahota is working on answering a question just like this...

[Sanjeet_Sahota]

5.  I was working on a similar but slightly different project.  As for feasibility of this, technically it is capable but currently unavailable with a response time below 10ms as Charles outlined above.  @Benoit_Barbalat So that we can understand the application better, can you provide the use case of why 10ms readings are critical for frequency?  Is this being used in a control scheme? Or can the data be retrieved differently?  Is there support for other protocols we can look into?

[Yut]

The basic module the Power Meter Module update output every 1 sec.

More over we use conventional Current = Coulomb/1 sec. all electrical parameters will be update at every 1 sec.

There is HS Power Meter Module but it is used for PQ analysis.

[greg_expoenergy]

Hi Benoit,

I think you need to provide more detailed information as to the customer's actual supervisor requirements.

All meters have a front end data acquisition system which generally samples at 10-200KHz which are termed the instantaneous values. But generally, these are not made available unless they are PQ meters.

These values are then aggregated and converted to RMS and which are generally available every 1 sec but in some more advance PQ meters one may get aggregated values every half-cycle.

I am very skeptical that one will be able to reliably and consistently retrieve and update values via MODBUS TCP in 10msec.

I would rather suggest that any time-critical functions be done in ION DESIGNER and downloaded to be processed on the meter itself rather than remotely as MODBUS (OPC and many others) are not really suited for time-critical processes. Any time critical stuff should be done locally and not remotely unless it is slow remote switching or signaling.

That is why PQ data, for example, is all done within the meter, stored and made available for downstream post-processing.

Otherwise one should, for example, consider the ABB  AC800PEC which is designed for such purposes. mAybe Schneider has some equivalent but I am not aware of this.

[Benoit_Barbalat · Accepted solution]

Update! The customer needed 20ms period for max 20min. So a max of 60,000 logs.

We tested the solution last week and here is what we did:

Here are the settings of the data recorder. It was set to "stop when full":

We did a small control page in Vista:

Customer had to reset the recorder, then enable recording for the duration of test.

Because there was so many logs to be downloaded at once, Loginserter took some time, that's why we had the views on the buffer and number of records left. Diagnostic Viewer could also help us see that Loginserter was working properly.

Overall, worked beautifully !

[Charles_Murison]

Hello @Benoit_Barbalat ,

Thank you for the update, glad to hear that we were able to help customer.

Regards,

Charles