?Therefore I would like to specify two different grounds. Is this actually possible in LT spice?
There's nothing stopping you from having any number of so-called "grounds" (in sloppy electrical circuit parlance), as long as you give all of them different names. ?GND1, GND2, ground3, myground, etc. ?They are just nets with net names.
The unique Ground symbol couldn't be used for them all, of course.
Do you need a "ground" symbol on your schematics for the different grounds? ?You could create your own unique symbols and use those. ?LTspice itself does have a second symbol, COM, which you can use however you wish. ?All it is, is a node, which isn't the same as GND (= node 0). ?It has no other significance.
The only LTspice requirement, is that every circuit node must have a DC path to GND. ?That's because LTspice needs to calculate the actual voltage on every net, relative to GND, and in order to do that, the DC circuit must have a conductive path that eventually leads to GND.
Some people don't seem to like that, if they have a circuit with an isolation transformer that keeps a part of their circuit actually isolated from the GND that appears elsewhere in their circuit. ?But it really doesn't matter. ?If the isolated portion is truly isolated, then it will function just as well if they connected it to GND anyway ... or to 7V, or to 7 million volts ... right? ?So, for circuit simulation purposes, it works fine to simulate it with the "floating" part connected to GND, either directly or through a big resistor. ?There just needs to be SOME path back to GND.
