By Paul Monies Business Writer pmonies@oklahoman.comLITTLE ROCK, Ark. — An unassuming building nestled on a wooded hillside next to the Southwest Power Pool headquarters is key to keeping the lights on for electricity customers in Oklahoma and parts of 13 other states. What goes on inside the SPP's operations and data center isn't top secret, although security is tight and employees have to follow strict reliability, critical infrastructure and electricity market protocols and guidelines.