Dan,
Our philosophy here has been that no critical control parameters are passed
across the node bus. We use parameters passed across the node bus for
control "enhancements" only, with appropriate error propogation, detection,
and handling of the parameters involved. For example we have manually
initiated runbacks of our Reactor Recirculation MG sets to a level based on
a total steam flow signal passed across the node bus from our feedwater
control system. We check the passed parameter for a propagated error (which
would include the loss of communications - I think the parameter is OOS in
this case), and disable the manual runback in the event of an error. All
critical parameters between the different CPs/control systems are hard
wired.
All that said, depending on the control system and parameters involved, if
the consequences of a failure are not significant and response time is not
significant, I woudn't hesitate to pass parameters across the node bus. As
we do not have the LAN bridges, I don't have a feel for how reliable those
communications are.
Thanks,
Gaylon Hicks
TVA - Browns Ferry Nuclear Plant
> ----------
> From: Murphy, Daniel J[SMTP:[EMAIL PROTECTED]]
> Sent: Thursday, March 30, 2000 4:53 PM
> To: 'Foxboro DCS Mail List'
> Subject: RE: Detection of nodebus-failure
>
> I would be interested to know what the concensus is out there for doing
> regulatory control across the carrier-band LAN. For example, one PID block
> in one node talking to an AOUT block in another node.
>
> Here we don't trust the CB-LAN to do basic regulatory control. We prefer
> to
> hardwire the signal via FBM's. Anyone else do the same?
>
> The same question applies to peer-to-peer communications within a node.
> Anyone hardwire these connections as well?
>
>
> Dan Murphy
> BP Amoco Refinery
> Brisbane Australia
>
>
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