I meet with some problms when simulating tranmission line.

I'm simulating a step voltage applying on a transmission line for my high-voltage course. I'm very confused that the system seems to be time-varying. This is my circuit:

I want to simulate the situation when a step voltage is applied on a transmission line(open circuit). But the wave differes with "step time" of the step block varying.

When "step time" is 0.004:

But when "step time" is 0.005:

I am very confused and want to know why.

This is the parameters of the line:

Answer 1

[Joel Van Sickel]

Hello Xiaobo,

this is due to the particular transmission line settings. As it is lossless, and in a simscape network with no losses, it is very problematics for traditional variable step solvers to calculate accurately. This shouldn't be an issue once you are simulating something more realistic. To fix this, switch your simscape solver configuraiton block to a fixed time step. 1e-6 will work, but maybe you can use something larger and still get good results. Otherwise, I would use one of the other methods to model your transmission line such that it does include losses.

Regards,

Joel