Hi All
I have been asked by a client to research the use of Rogowski Coils
(RC) as current sensors in an integrated protection solution in MV
switchgear.
I have downloaded 20 plus papers and articles on the subject. The
advantages and disadvantages of RCs compared to iron-cored CTs are
well do***ented, and well understood by me.
What I can't get a solid grip on is a universal technique for
reproducing the primary current in a RC by digitally integrating the
secondary voltage.
If the primary current is a stable, or slowly varying, sinusoid, then
standard (simple !) integration methods accurately reproduce the
primary current from the secondary voltage. This is fine for
measuring slowly varying currents, as in metering applications.
If the primary current has a significant transient DC component, then
a well-regarded protection technique is to forget about integrating
the RC secondary voltage, just time ****ft it by one quarter cycle. The
RC itself will remove almost all of the DC component, and the
protection algorithms will work just fine.
But, if we are interested in oscillography (waveform capture) -
recording the primary current under typical fault conditions with a
high transient DC component, is there a reliable digital integration
method that will achieve this ??
From my own crude theoretical analysis of the sharp transition from
zero or low 50 Hz current to a high 50 Hz current with a transient DC
component, I can't see how it is possible to accurately reproduce the
transition step in the primary current by integrating the secondary
voltage of an RC.
I have also tried lots of numerical simulations of this problem, and I
can't come up with an integration method that accurately reproduces
the primary current in a RC under these transient conditions. My
tests can reproduce the primary current when it is stable, but not
when it is in transition from low current to high current with a
transient DC component.
Hoping you can help
Mister Kev
Kevin O'Hare
MegaVolt Consulting
ABN 63 993 497 703
Email mrmvolt@[EMAIL PROTECTED]
/ Fax 61 7 3348 2432
Cell 0412 642 949
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