10hp down hole centrifugal pump.Set at about 70 feet.Pressure measured and found at center of BEP.Rated flow 90g/min.
Actual measured flow 85g/min.230V 3ph.Supply voltage 241V - all phases within 0.5V,Wire size from measured point to pump 6AWG.Rated current 30A
I suppose my perspective on system curves may be particular to my industry.  But, in the best example I can see in my plant that relates to the original question, a system curve is both impossible and unnecessary.  Our well pumps pump into headers that may be fed from many sources and deliver water to many users.  The header is pressure controlled with one or more pumps that are on some sort or pressure control.  There may be some variability in the pressure of the header. But, it can't be put into the form of a system curve.  I could spend a month trying to model the system with all combinations of contributors and users. 
But, as I said, the system curve for my well application would also be unnecessary.  If the header is pressure controlled to run between 95 and 105 psi, then I know all I need to know.  I have almost never seen an application in my plant where a system curve is important except at original design or redesign.  But, with vary rare exception, all of our streams are flow controlled.  And, when I need to evaluate pump performance, it is done at discrete points in time where I only need to know the suction conditions, discharge conditions, product properties and flow rate.  If I had a problem that might require evaluating a system curve, it would probably be a situation where the control valve reached 100% and the flow controller couldn't reach set-point.  Then I would need a system curve (or at least a couple of points on a system curve) to determine if I can achieve the target flow rate best by making changes to the pump, control valve or system.

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