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Thread: Connection Timeout When Remove DO Card from RTU

  1. #1
    Join Date
    14.09.2017
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    24

    Default Connection Timeout When Remove DO Card from RTU

    Hello,

    I have a project requirement, where I need to find out the acknowledgement of Action Variable command initiate and execute successfully.
    For that I am using COT reference of command variable i.e. if COT-7 Command Select and COT-10 Command Execute (Suggest me whether it is right or not)

    Setup Information (Zenon 8.10 Build 65969):
    1) I had create a command processing with switching commands for ON and OFF operations for command variable and attached it to Action and response variable. In variables checked Select Before execute checkbox for command and response variable.
    2) After connection established when I provide command to action variable it properly executed.
    3) Now to check conditions for acknowledgement status of Action variable, I had removed DO card from RTU and check we get COT as 6 where we can define after some delay that connection is not established.
    4) When I reinsert the DO card to the RTU and send Select command then it again goes into the timeout. I Checked the same in Wireshark log where found that select action regarding information is not provide from SCADA to RTU wireshark log after removing the card.
    5) For proper execution I need to restart the zenon.
    6) same I have checked with other client where I found connection reestablishment takes place without any error.

    For reference I am attaching wireshark file (SCADA IP:172.20.41.1 RTU IP:172.20.41.51)
    Events takes place as follows:
    1) SCADA Start -> provide ON/OFF commands to the action variable -> remove DO card -> Provide select command (2 times after delay about 1 min) -> Insert DO Card -> Provide select command 3to4 times.

    Regards,
    Rahul.
    Attached Files Attached Files
    Last edited by rahulindore05 : 19th November 2020 at 07:59

  2. #2
    Join Date
    01.07.2008
    Location
    Salzburg, AT
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    923
    Best Answer

    Default Re: Connection Timeout When Remove DO Card from RTU

    What driver are you using? in zenon all energy drivers are mapping/transferring the COT to the Runtime. IEC870, IEC850 or DNP3?
    Forum is not the right place to request analyzes of sniffs, I will not open a file from a public forum. If you want that an expert do the check of your fies, then contact your local COPA-DATA support officially.

    From the description of the issue I'm guessing that the RTU is not responding the commands at all, neither positive, nor negative. And/or maybe that you had configured in the Actions very long Timeouts. 


    ad. what is the COT 7 and 10, is COT 7 the Select and COT 10 the Execute?
    NO, you wrong. Maybe the Help helps:



    And see also: Manual > Energy Edition > Command Processing > Operation in the Runtime > Execution of a command > Select before Operate > SBO - no reaction from the PLC


    So: when you press the action button, then the driver sends to the RTU the Select - this means that COT=6 and SE=1. As reaction the RTU must respond COT=7 and SE=1 and PN=0 (positive) or PN=1 (negative). As long as there is no response from RTU the command processing waits. The RTUs need time to e.g. check interlocking conditions, and the protocols are not defining how long it could take; zenon waits.

    After positive response on Select the master is allowed to send the Operate/Execute command - the driver sends again COT=6 but with SE=0. Then - in positive case - the RTU responds with COT=7, and then - after RTU completed the command - it responds with COT=10 (RTU sends two responses).
    Attached Thumbnails Attached Thumbnails k8LHlKyFSK.png   aST8HuTxOH.png   tIxoCpmtFO.png  

  3. #3
    Join Date
    14.09.2017
    Posts
    24

    Default Re: Connection Timeout When Remove DO Card from RTU

    Hello,

    Thanks for the valuable response.

    I am using IEC60870-104 driver for the configuration.

    From the description of the issue I'm guessing that the RTU is not responding the commands at all, neither positive, nor negative. And/or maybe that you had configured in the Actions very long Timeouts.
    Action timeout in command processing mentioned 30sec but after 1 min also there is no such response found in Wireshark that it sends COT=6 and SE=0 to RTU, until we refresh driver and reload project or start zenon runtime again.

    Thanks for the information provided regarding COT.


    After positive response on Select the master is allowed to send the Operate/Execute command - the driver sends again COT=6 but with SE=0. Then - in positive case - the RTU responds with COT=7, and then - after RTU completed the command - it responds with COT=10 (RTU sends two responses).
    As you have mentioned Positive Case, does it depends on any hardware condition of RTU (e.g. Relay faulty or Healthy)?
    Can you just brief the condition for positive case, how exactly does it work?


  4. #4
    Join Date
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    Default Re: Connection Timeout When Remove DO Card from RTU

    hmm, I see I have to repeat the explanation using another words.. ok, the second try to explain:

    When the user press action button then the driver sends to RTU the Select - In Wireshark it is C_DC_NA_1 Act, where in IOA -> DCO -> S/E is true
    Then the action waits on the response from RTU.

    The RTU must respond, but the IEC 60870 standard does not define the time limit. So, also in the negative case, the RTU must respond; sooner or later. In Wireshark the negative response would be C_DC_NA_1 ActCon, where Negative is true (and S/E the same as it was in C_DC_NA_1 Act).

    If you do not see this response in Wireshark, then the RTU is not standard compliant. Then, contact the manufacturer of the RTU and demand the fix.

    I'm not able to say why the action waits for this missing response from RTU longer as the configured timeout 30s; maybe because of some bug. For this not working timeout issue contact your COPA-DATA Support officially.
    Last edited by ursulak : 24th November 2020 at 10:18

  5. #5
    Join Date
    01.07.2008
    Location
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    Default Re: Connection Timeout When Remove DO Card from RTU

    >As you have mentioned Positive Case, does it depends on any hardware condition of RTU (e.g. Relay faulty or Healthy)?

    Ask the manufacturer of the RTU when it responds the commands positive and when negative.

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