Harmonic Analyis
Harmonic Analyis
(OP)
Hi, Guys,
As per IEEE519, Isc is maximum short circuit current available at PCC. But the source short circuit current we based on to perform the harmonic analysis should be minimum short circuit level, which represents the worst case senario. Is it correct. This is as per IEEE-519 new revision. another question is, is the short circuit half cycle value or 1.5-4 cyle or steady state value? It is so clear in IEEE 519.
Appreciate it if somebody can shed some lights.
As per IEEE519, Isc is maximum short circuit current available at PCC. But the source short circuit current we based on to perform the harmonic analysis should be minimum short circuit level, which represents the worst case senario. Is it correct. This is as per IEEE-519 new revision. another question is, is the short circuit half cycle value or 1.5-4 cyle or steady state value? It is so clear in IEEE 519.
Appreciate it if somebody can shed some lights.






RE: Harmonic Analyis
RE: Harmonic Analyis
In our case, all the LV VFDs come with input filters. As per the vender design, all the filters are tuned filter. Not sure we need to check the resonance or not in the system. Our system is very strong.
RE: Harmonic Analyis
The short circuit impedance shall be the continuous one. As per IEC 60909-0, it shall be the steady-state short-circuit current (Ik, the r.m.s. value of the short-circuit current which remains after the decay of the transient phenomena). Because, the harmonic current injection to the system is generally a steady state phenomena.
RE: Harmonic Analyis
RE: Harmonic Analyis
RE: Harmonic Analyis
The value of angle doesn't matter as long as the angle is same for all the harmonic sources.
RE: Harmonic Analyis
RE: Harmonic Analyis
Agreed, your point is right on its own. But Hamid's problem is with the phase angles of the harmonic currents injected from various sources and my response was for that.
Imagine, when all the harmonic (say fifth harmonics)current injected have the same phase angle, that means the current wave would rise and fall together. When all the waves are rising and lowering together can cause higher distortion. Same as the vector sum of in phase components is higher than the out of phase components.
Now, say the injected harmonic components starts at different values. Thus the vector sum of these harmonic components is relatively lower due to their phase shifts.
Thus the severity of in phase components is much higher than the out of phase. This makes the same phase angle more conservative.
Hope I am making it clear.