IEC61850 to Modbus

[DeepakDeb]

Hi, I have a case where I need to use Zenon as a gateway to convert 61850 signals to Modbus. Client has a requirement to run the gateway in a Linux system that will be connected to the SCADA. Hence I assume that logic processor can be used (not process gateway). See below a rough sketch how I assume it can implemented based on my understanding. PL let me know if such architecture is possible.
Incase this is the right direction, can you please guide me how the project configuration has to be done.


BR,
Deepak

[ursulak]

yes, it is possible to use a straton RT running on another, independent device as MODBUS gateway, but this will demand significantly more work (and risk of mistakes) in comparison if you would take the zenon Process Gateway. I would propose you to run zenon Process Gateway an additional, dedicated PC (this PC can be a zenon Network Client). The architecture with zenPG means higher license costs but is fast done and easy to maintain - low time and human costs.

In architecture like on your picture: in zenon project you can create stratonNG driver manually to communicate with this independent straton RT. And you would have to create Allocations from iec850 variables to stratonNG variables (as many allocations as variables) for inputs (FC=ST, MX, CF etc.). And you have to create limits and write set value functions - from stratonNG variables to iec850 command variables (*/Oper.ctlVal[CO]). Then zenon will "copy" the data between 850 and straton RT.

In straton RT all variables can be available for some additional system via MODBUS slave (is on board).

[DeepakDeb]

The reason I am exploring this architecture is that the customer expects to use LINUX based system for the interface towards the north side. Hence this is the only option I could think of. I believe the process gateway doesn't support LINUX.

Moreover, I have noticed that the process gateway doesn't support the Input register, Discrete inputs in Modbus.

The number of variables for this project would be approx 10000. Hence the optimal performance is a cornerstone for this project.

How would you consider the performance of process gateway vs STRATON logic processor?

[ursulak]

zenon Process Gateways are running only together with zenon Engine Service (Runtime), so not yet on LINUX.

The MODBUS protocol is an old, polling protocol with relatively small frame size, so i would expect that the eventual performance limits would appear in the MODBUS communication, not in the slave (whatever kind you will choose). A MODBUS master has to periodically (e.g. 1s) send read request for all (in your case 10k) variables and evaluate the responses, so also about those variables which are not changing values. 

For the performance in transfer from 61850 to a MODBUS slave not the quantity of variables cares, but the quantity of events (value changes) per second. As well zenon to zenPG, as stratonNG driver to straton RT, are transferring events spontaneously on change (not polled). Thus, in both solutions, i would expect that eventual performance limits are not zenon/straton, but in MODBUS TCP and/or "customer SCADA".


The data transfer between zenon and zenPGs via Windows COM interface consumes CPU on a single thread (thus, it occupies a single CPU core) the max rate of events (value changes) per second depends on processor / Windows version etc. I'm currently testing another zenPG on a PC with i9 processor and transferring 15k-20k [events/s] (on 100k variables).

The data transfer via stratonNG driver goes via TCP and the straton RT running in cycle has to evaluate received data. Thus hier the max possible event rate depends on the cycle time and calculation time (your program) in straton RT.


Without a practical test using your HW and application, it is not possible to estimate which architecture would be (probably only slightly) faster. I suppose the answer on this question is not relevant anyway, as more difficult would be to setup the MODBUS communication and - if your 10k variables are all changing frequently - to prepare MODBUS master to acquire and evaluate the data fast enough; else the master is not sending polling requests on expected time and/or blocks the TCP socket and slave (zenPG or straton RT) has to wait.

[diyagabri]

The customer expects to use a LINUX-based system for the interface to the north side, which is why I'm looking into this design. As a result, this is the only solution that came to mind. The process gateway, I suppose, does not support LINUX.

In addition, I've found that the process gateway in Modbus does not support the Input register, Discrete inputs.

This project would have approximately 10,000 variables. As a result, optimal performance is a key component of this project.

What are your thoughts on the performance of a process gateway against a STRATON logic processor? drift boss

[ursulak]

The performance by 10k signals via MODBUS protocol? Hmm, MODBUS is a polling protocol (not spontaneous: not on data change and not only the subset). It means the remote MODBUS-Master ("Customer SCADA") must read periodically all signals (so 10k) to check which had changed the value. Thus, I would rather question what poll period do you plan, and if then the traffic on the connection and this Master would be performant enough. 

The transfer via MODBUS-Slave in straton could depend on straton cycle (by synchronous to the cycle, but I'm not sure), then the data exchange between program and fieldbus drivers is once a cycle. Thus, if transfer takes long - it could slow the cycle (cycle overload). What do you estimate, how many of those 10k signals would change the value during one cycle?

The zenon Process Gateway runs for sure independently. Thus, I would expect the zenon based solution could be more performant, but we never made the test to compare.

The bottleneck is anyway the MODBUS protocol concept.