A Public Service Commission (PSC) is a state agency that regulates utilities. To locate the regulations and publications of a particular state's PSC, visit the PSC's web site and/or see the entry for the individual state.
Debt rating agencies and other financial institutions rate the PSCs based on their friendliness to the state's utilities. According to a post on the BusLib listserv by Charles Shellabarger on September 5, 2008, you may be able to find out the rating by (a) contacting the relevant agency or institution, or searching the relevant web site (b) looking up a regulated utility in ValueLine and see the bottom of the page and/or (c) using Regulatory Research Associates (part of SNL Financial).