NY -- Standard&Poor's CreditWire 9/18/97 -- Standard&Poor's today assigned its single-'B' rating to Tucson Electric Power Co.'s aggregate $247.46 million unsecured industrial revenue bonds, issued by the Industrial Development Authority of the County of Pima (Arizona). The issue comprises three series as follows: -- $22.46 million industrial development revenue bonds, 1997 series A, due Sept. 1, 2025; -- $150 million industrial development revenue bonds, 1997 series B, due Sept. 1, 2029; and -- $75 million industrial development revenue bonds, 1997 series C, due Sept. 1, 2029. The company's corporate credit rating is double-`B'-minus. The outlook is positive. Tucson Electric's speculative-grade rating reflects a weak business position combined with extremely frail debt protection measures. Risks, such as