NEW YORK--(BUSINESS WIRE)--Fitch Ratings rates Southwestern Public Service Company's (SPS) $200 million add-on issuance of 3.30% first mortgage bonds (FMBs), Series No. 3 due June 15, 2024 'A-'. The FMBs rank pari passu with SPS' existing secured debt. The Rating Outlook is Stable. Net proceeds will be used for the repayment of short-term debt and other general corporate purposes. KEY RATING DRIVERS Challenging Regulatory Environment SPS operates in Texas and New Mexico, under the jurisdiction