Megawatt Transducer Calibration
Megawatt Transducer Calibration
(OP)
Hi,
We are trying to check the calibration of a MW transducer and display gauge. The meter is configured for 2 CT inputs and 3 voltage inputs. Unfortunately, the technicians test gear isn't too happy creating the wye-connected B-phase-grounded system that the transducer is expecting to see.
Does anyone have any bright and simple ideas for testing this? I'm thinking of either insulating the meter case and connecting B-phase to the meter ground terminal (a nuisance, as some of the transducers are awkward to remove), or attempting to scrounge 3 small isolating transformers (we are in a remote area, so may not be able to find any).
Thanks.
We are trying to check the calibration of a MW transducer and display gauge. The meter is configured for 2 CT inputs and 3 voltage inputs. Unfortunately, the technicians test gear isn't too happy creating the wye-connected B-phase-grounded system that the transducer is expecting to see.
Does anyone have any bright and simple ideas for testing this? I'm thinking of either insulating the meter case and connecting B-phase to the meter ground terminal (a nuisance, as some of the transducers are awkward to remove), or attempting to scrounge 3 small isolating transformers (we are in a remote area, so may not be able to find any).
Thanks.






RE: Megawatt Transducer Calibration
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Megawatt Transducer Calibration
I'll ask around, but I don't think that we have anything capable of measuring power factor to give us a reliable way of calculating MW based on the VT and CT signals while running.
RE: Megawatt Transducer Calibration
If you cannot measure, you can perhaps add known loads and see what display best reflects the added load. That one is probably correct.
Gunnar Englund
www.gke.org
--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Megawatt Transducer Calibration
Bill
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"Why not the best?"
Jimmy Carter
RE: Megawatt Transducer Calibration
Alan
Democracy is two wolves and a sheep deciding what to have for dinner. Liberty is a well armed sheep!
Ben Franklin
RE: Megawatt Transducer Calibration
If so the test set shouldn't have a problem with it. Use the voltage neutral as B phase and connect to B input, set A phase to 30 degrees and connect to A input, set B or C phase of the test set to 90 degrees and connect to C input. (that creates a delta PT secondary connection) Connect the currents as they are labeled and it should work. Then to change the power factor rotate the currents as needed.
RE: Megawatt Transducer Calibration
After a night's sleep, I have gone through the vector diagrams, and once the test set is free, will provide the following voltages from the test set:
Va-n: 120V angle 0
Ia: 5A angle -30
Vb-n: 0V
Ib: 5A angle -150 (note, not connected)
Vc-n: 120V angle 60
Ic: 5A angle 90
I believe that this will give me the same voltages and currents as the meter would normally see with unity power factor.
If this doesn't work, we will connect an oscilloscope and check the voltages and currents with the unit running, and calculate power manually to check against the meters.
Thanks.
RE: Megawatt Transducer Calibration
I find just shifting the voltage once by 30 degrees then moving the all the currents around to change PF makes things simpler and less error prone. That way at PF of 1 the currents are 1, -120, 120 degrees.
RE: Megawatt Transducer Calibration
RE: Megawatt Transducer Calibration
Have you considered a single-phase test? Series the current inputs and parallel the potential inputs.
RE: Megawatt Transducer Calibration
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If we learn from our mistakes I'm getting a great education!
RE: Megawatt Transducer Calibration
Regardless, we have injected the currents and voltages into two sets of meters as suggested by pwrengrds, seemingly successfully - one set of meters seems to have inserted a 10 degree phase shift into it's readings, the other appears to be scaled incorrectly in SCADA.