Is Texas the only state with a private power grid?

I'm curious to know, is Texas indeed the sole state in the nation to operate its own private power grid, distinct from the larger interconnected grid system? It's a fascinating aspect of the state's energy infrastructure, and I'm wondering if there are any other states that have taken a similar approach to energy generation and distribution. Could you elaborate on the specifics of Texas' private grid and whether there are any advantages or challenges associated with this unique setup?