I want to know if there are any issues with the internal tv tuner cards. Because we are connecting to the motherboard. If any reverse currents happen then the mother board will have a problem.
There aren't any more issues with TV cards than on any other expansion card. Basically every expansion card which has any input/output can destroy your motherboard if you improperly connect it (like for example connecting power cord into antenna input).
TV cards aren't inherently any more dangerous than say fax modems or network cards, so I wouldn't worry too much.
If your area has problems with bad weather, you could consider purchasing a surge protector with antenna plug. This way if the coaxial cable for antenna/cable television is hit by a lightning, surge protector should save your PC.
I also wouldn't worry too much about badly designed card damaging the motherboard. There are tests which card needs to pass in order to be sold and I doubt that any card on the market will cause any damage. Still if you want to be 100% sure, go for cards from manufacturers which have good reputation in your area.