IEC61850-7-5 #6555

Behaviour of output contacts when LN is in blocked mode

Added by Keith Gray 4 months ago. Updated 23 days ago.

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TF 7-5 Project document:
IEC 61850-7-5

Updated by Keith Gray 4 months ago

This was assigned to 7-5/7-500 TF during the 7-5/7-500 meeting in Kista, Sweden on 2023/10/25.


Updated by Michael Haecker 27 days ago

Part 7-1 says: "The mode blocked (Beh=test/blocked or Beh=blocked) shall be interpreted as the mode which explicitly disables any physical outputs having an effect on the process."
Part 7-4 says: "No (wired) output data (digital by relays or analogue setpoints) will be issued to the process."

Once LN.Beh="blocked" or "test/blocked", then the blocked LN instance shall not change the output status.
Activation of blocked mode shall not cause a spontaneous change of any output. Since the standard cannot know whether a project uses an active high or an active low output signal, the standard cannot define the inactive output status. Any output change could be interpreted as a signal to the process.
LN.Beh="blocked" or "test/blocked" freezes the output in its actual state.

Testing a control command against the 'LN.Beh' is typically done before a control is processed.

To be discussed: Activation of blocked mode during a switchgear operation. Option: to complete the switchgear operation before blocking the output for further actions. Rational: The switchgear must not be damaged due to activation of blocked mode. Proposal: Activation of blocked mode does not force the output to return to an inactive output state.

To be discussed: Blocking of the entire IED (LD0/LLNO.Beh) does not affect the watchdog output.


Updated by Keith Gray 23 days ago

  • TF 7-5 Project document IEC 61850-7-5 added
  • TF 7-5 Project document deleted (-)
2024/02 WG10 Meeting Discussions:
  • Michael presented his response
  • Tom suggested that the block is only checked at the time a control request is received
  • What does this mean for an analog setpoint output?
    • Blocking a change?
    • Setting to a known value?
  • Are we only talking about block command send to mod or are we also talking about command blocked?
    • Only talking about control mod blocked.
  • Reaching consensus that a command to block should not interfere with an ongoing command:
    • If a user puts the LN into blocked mode but just before that a protection trip is issued, we don't want that trip contact to be interrupted until the breaker/switch is open

Open Questions:

  • Should the update of beh be delayed because a command is in progress?
  • Also need to consider what happens if mod/beh is set to off while an existing control is running?
    • Should consider all of the change of states for ongoing commands
  • "Freeze" current output state?

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