After apply different types of fault on IEEE 14 bus system the wave form is not correct why?

I make a model for IEEE 14 bus system at normal case the wave form is pure sine wave after applying different types of fault and put switches to apply fault in a certain time the wave form not correct how can I solve this problem??

This is a home "Electrical-Lighting" forum, not a forum for electrical engineering. Wave form analysis and or IEEE 14 analysis are way beyond the scope of this forum.