measure sequence

[ftova]

hi everybody

i need help about how measure Positive, Negative y Zero sequence voltages and currents
url`s, pdf`s or comments are wellcomed

thanks in advance

Fredrick

 

[magoo2]

Do a search on symmetrical components. Most protective relay manufacturers have info on their sites, like SEL and Basler.

 

[cuky2000]

Zero Sequence: With a window CT the three in wye-connected system would have a current in it equal to 3Ia₀. Also if each phase current is known, the average values (including the phase angul) will be equate to the zero sequence

Positive Sequence: Is the average value of adding the phase current A plus the current on phase B shifted 120⁰ plus adding the C phase current shifted -120⁰ will be equivalent to the positive sequence current.

Negative Sequence: Is the average value of adding the phase current A plus the current on phase B shifted -120⁰ plus adding the C phase current shifted 120⁰ will be equivalent to the negative sequence current.

Similar approach can be used for the voltage.

 

[davidbeach]

There are a few ways of measuring 3I0 or measuring 3V0. Other than that, what's measured is nearly always phase quantities and the sequence quantities are calculated rather than measured. Almost anything I work with these days the residual current (3I0) is always calculated unless it's the 3I0 in the neutral of a transformer. I can't think of any new installations where we'd attempt to measure 3V0.