Homework: TEM wave after switching
I also tried to simulate the circuit, according to which the voltage
  never exceeds 45V.


Of course it won't be any different to 45 volts - you have a perfect voltage source (45 volts) and you are measuring it at distance Z = 0. It will always be 45 volts at zero distance because, it's a perfect voltage source and this will override everything except a perfect short circuit (indeterminate solution).