In my first experience using a SEL 3350 RTAC (or any RTU), I found setting up Modbus TCP functions, both as a server and client, to be quite straightforward. However, I am unsure about how to efficiently write a block of data to around 40 Holding Registers in an IED at regular intervals, such as once per second. Any recommendations on the best method for achieving this task without relying on the Tag Processor, which operates at a faster cycle time of 100ms than necessary for my Modbus data writing requirements?
Utilize the tag process or Structured text to input data into MODBUS_HREG_xxxx.oper.ctval and create a basic program for trigger manipulation. Implement a timer that increments to 10 before resetting to 0. Upon reaching 10, the MODBUS_HREG_xxxx.oper.trigger will switch between true and false. This method allows for efficient data tracking and control.
I've worked with Modbus quite a bit and in your case, a solid method could be to create a timed function that writes to batches of these registers. Using a time-triggered logic function, you can set your RTAC to write to the desired holding registers every second. This approach bypasses the need to rely on the Tag Processor and allows you to customize your write intervals specifically to your project needs. However, it's important to remember that the successful execution of such tasks usually depends on the network latency and the processing capability of the IED. It's worth running some tests to ensure everything operates as expected!
From my experience with SEL 3350 RTAC, if you need to write to multiple holding registers at an interval of 1 second, I would suggest using an Advanced User Program using C# or Structured Text. This way, you can control the execution rate precisely. In the program, you'd employ the "WriteMultipleHoldingRegisters" command of the Modbus TCP Master protocol. It is efficient as it allows writing up to 123 registers at once. Make sure to handle exceptions and communication losses, as these are network operations that could fail for various reasons. Also, keep in mind that larger blocks of data take more time to process and transfer, but given your 1-second cycle, this shouldn't be a problem. It will definitely work more efficiently than using the Tag Processor for this particular instance.
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Answer: To efficiently write data to around 40 Holding Registers in an IED on an SEL 3350 RTAC, you can consider implementing a custom solution using Modbus TCP functions as a client. This allows you to achieve the desired data writing frequency without relying on the Tag Processor.
Answer: Yes, it is possible to write data to Holding Registers on an SEL 3350 RTAC without relying on the Tag Processor. By setting up Modbus TCP functions as a server and client, you can efficiently write a block of data to the Holding Registers at the required intervals.
Answer: The recommended method for writing data to Holding Registers on an SEL 3350 RTAC while meeting Modbus data writing requirements is to create a custom solution using Modbus TCP functions. This approach allows you to achieve the desired frequency of data writing without being limited by the cycle time of the Tag Processor.
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