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I'm trying to write a logic statment using labview8 to create a distance relay (grounded)

I'm trying to write a logic statment using labview8 to create a distance relay for a power system lab ( i want to teach next semester), I'm using NI6025E to collect both Voltage and Current, I'm diving Voltage RMS by Current RMS to get impedance. If the Impedance value is less than X I want immediate action (send a false signal to the digital output port that is normally true), if it's greater than x but less than 2x i  want the same action to happen but not immediately maybe 5seconds later.
Does anyone have any idea on how to achieve this delayed action?
or Even has anyone here used a DAQ board and Laview to create any type of protection relay, over cuurent, differential or impedance?
My main problem is delaying action, for breaker (SCR switch) coordination
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You can use a case statement and the wait function found in All Functions>>Timing. I think that using the wait function should do what you're looking for but if not, post to let us know!
Chris C
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I tried using the wait function but that ends up slowing down everything in the while loop including the Data Acquisition, And eventually the same tripping I didnt want to occur will still happen.

When I get back to lab tommorrow I attach a copy of the VI.

Thank you Chris
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So then it sounds like you want your while loop to run at a fast rate but only slow down part of it. Of course this condition can't be logically met, but you can use parallel while loops in a producer consumer architecture. This is a concept we at NI teach in our LabVIEW basics course. If you're interested in taking the course, please refer to the LabVIEW Basics 1 page.

Also, LabVIEW ships with a producer consumer architecture template and can be found by going to file>>New...>>From Template>>Frameworks>>Producer/Consumer. You can also find examples like Queue to Pass Data.

This isn't the only way to accomplish your goals, it's just the first that pops into mind.


Chris C

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