Problem with SR489 Multilin 1

[Ealberto]

Hi everybody, I'm getting a problem with one SR489 Multilin, one of its analog output sudently change signal level, This refers to MVAR, and is calibrated to:
4mA=-3.37MVAR to 20mA=3.37MVAR. At normal power factor it got 0.9MVAR but sudently it increased to maximum setting (3.37MVAR). I did changed the input analog module on PLC in order to eliminate this posibility. I see the problem is with SR489 relay. What can I do, in order to fix it? Thanks for your help.
Ealberto

 

[dpc]

If you set 4mA AND 20 mA equal to 3.37 MVAR, that's pretty much what you're going to be reading. I assume the 4mA should be set to either 0 or -3.37 MVAR. If the MW and MVAR are reading correctly on the meter, problems with the analog output must be related to the scaling factors, a wiring problem or a hardware problem in the 489. I'd suggest putting a 1 ohm or similar precision resistor in series with the 4-20mA and checking the voltage. This will enable you to determine the current output from the 4-20mA.

Don't forget that the MVAR can be positive or negative.

 

[ScottyUK]

Hi dpc,

4mA=-3.37MVAR

There's a '-' symbol there. I didn't spot it either at first read. Agree with the rest. I'll enquire whether we've had anything similar with our Multilins.


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If we learn from our mistakes,
I'm getting a great education!

 

[dpc]

Sorry, I missed the minus sign. My bad.