Power Transmission Line and Transformer Parameters

[Physicist3]

Hi,

I was wondering if it would be possible for someone to help me clarify a few things regarding transmission lines and transformers?

For a Power Transmission line, what exactly is the mutual coupling between phases of a 3 phase line? Is this the same as the shunt capacitance and if not, what exactly is the shunt capacitance? Is the series resistance and inductance of a transmission line simply the resistance and inductance of each of the 3 lines separately and not taking into account linkage between the lines?

For a transformer, am I correct in thinking that on no-load, the current drawn from the primary is used to supply the magnetising current required for production of a flux around the core, and also for supply of the losses within the core (eddy current and hysteresis). What exactly is the magnetic impedance and the leakage as these terms confuse me somewhat? Also, when a TXFR is on load, are the additional losses simply the I^2R
losses in the windings due to the winding resistances?

Thank you in advance

 

[zoki85]

For a Power Transmission line, what exactly is the mutual coupling between phases of a 3 phase line? Is this the same as the shunt capacitance and if not, what exactly is the shunt capacitance? Is the series resistance and inductance of a transmission line simply the resistance and inductance of each of the 3 lines separately and not taking into account linkage between the lines?

There are 3 phase to phase capacities and 3 phase to ground capacities. For example, capacity between phase A and B is defined as C_ab=ΔQ_ab/ΔV_ab, capacity between phase A and ground is C_a0=ΔQ_a0/ΔV_a0 etc. Similar definition is for mutual inductivities L_ab=Ψ_ab/I, where I is current circulating in loop of the phases A-B and creating mutual flux Ψ_ab. Also 6 of them. Mutual capacities and inductivities depend exclusively on the geometry of the system.

For a transformer, am I correct in thinking that on no-load, the current drawn from the primary is used to supply the magnetising current required for production of a flux around the core, and also for supply of the losses within the core (eddy current and hysteresis).

The current drawn is called a magnetizing current. It produces flux in the core, and only smart part around core. Yes, it supply losses within the core.
See wikipedia for more : http://en.wikipedia.org/wiki/Transformer

 

[anorlunda]

You could do a little Googling before posting here. I searched "transmission line equivalent circuit" and found numerous sources such as http://eee.guc.edu.eg/Courses/Electronics/ELCT908%20Distributed%20Power%20Systems/Lectures/Modeling%20of%20Transmission%20Lines.pdf

Same thing for transformers.

If you still do to understand after studying the courses, then you are welcome to post questions here.