When do you use low (crouching) throws?

I know they must be useful, but in fast paced play, I never know when to attempt them. I think ive landed a couple after blocking a low kick, but it seems inconsistent at best. I main tina and she has an attack that put oppenents into a crouching state for a throw. But beyond that its like I never get a chance to use them.

Any advice for setups or situations?