3 phase transmission line mutual coupling

[Physicist3]

Hi, if I simulate a three phase transmission line operating with a fault across two of the phases, would the mutual coupling have any effect on the current through each of the lines, as I have calculated the fault current values using symmetrical component analysis and the values are consistently slightly higher than those obtained from physical simulation testing using a three phase transmission line that I have constructed using an inductor and resistor in series per phase?

 

[zoki85]

The inductors values represent mutual inductive coupling between two lines in this case. Maybe you used values for line to ground return fault (which are close but identical)

 

[Physicist3]

What I have done is used a 3 phase inductive load bank to simulate a transmission line. I have then (using the known inductance and resistance values from this load bank), used symmetrical component analysis to calculate the theoretical currents through the system and these are all about 0.1A above the values measured from testing of the physical system. Because the calculations will not take the mutual coupling values between the phases into account, but the mutual coupling will still affect the measured results, would this cause the measured values to be slightly lower than the calculated ones?

 

[zoki85]

Inductivities (and hence reactances) of the conductors of a transmission line increase total reactance seen by source powering the fault. Therefore, the fault current will be smaller far away from the source.

 

[alphy]

I would like to clarify that mutual coupling is a phenomenon that occurs in closely spaced conductors where the magnetic fields of one conductor can induce currents in the adjacent conductors. In a three phase transmission line, mutual coupling is present between all three phases and can affect the current distribution among the phases.

In the scenario described, it is possible that mutual coupling is contributing to the slightly higher fault current values obtained through symmetrical component analysis. This is because the analysis takes into account the mutual coupling between the phases, while the physical simulation testing may not accurately account for it.

Additionally, the inductor and resistor used in the constructed transmission line may not accurately represent the behavior of a real transmission line, which can also contribute to the differences in fault current values.

In conclusion, mutual coupling can have an effect on the current distribution in a three phase transmission line, and it should be considered in both theoretical and physical simulations. Further studies and refinements in the simulation methods may be necessary to accurately predict the fault currents in a three phase transmission line.