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UTSA’s Redundant Transformers Virtually Eliminate Power Outages

(August 13, 2018) – I’ll bet you didn’t notice a power outage when CPS energy performed necessary maintenance on a 50-megawatt transformer serving UTSA’s Main Campus recently! That is because there was no outage, since UTSA is served by two redundant transformers designed to allow maintenance or even complete failure of a transformer without disrupting electrical power on campus.

Before 2005, UTSA’s Main Campus could expect at least a couple of campus wide electrical power outages annually. Aging infrastructure on the UTSA side and system design on the CPS Energy (CPS) side were the primary reasons for the outages that sometimes lasted for many hours. UTSA’s rapidly growing campus and electrical and reliability demands for research continuity meant that UTSA needed to upgrade their vintage 1973 electrical substation and distribution. This provided an opportunity for UTSA to work with CPS to upgrade their electrical supply to UTSA’s Main Campus.

The result is today’s electrical system. CPS has two each 50 megawatt (MW) transformers dedicated to supply UTSA’s Main Campus electrical power. UTSA’s highest electrical power peak to date is 18 MW, so each CPS transformer is capable of supplying almost three times our highest current peak. Another way of looking at this, each transformer can handle over two times our existing campus size.

The two transformers are both supplying UTSA’s Main Campus simultaneously through UTSA’s double ended switchgear substation. The CPS transformers are on different high voltage circuits on the CPS distribution system, thus if one circuit fails, the remaining transformer is capable of picking up the Main Campus electrical load without a power interruption. Additionally, since the transformers are on the high voltage circuits, frequent fault events seen on CPS medium voltage circuits, such as those caused by automobiles hitting transformer poles, will not impact UTSA

Having the redundant transformer alone improves the reliability of the electrical supply making it less likely we will experience an electrical power outage. On top of that, scheduling the recommended maintenance for each of the transformers with CPS is simple since one of the transformers can be shut down without any impact to campus operations. This leads to the required maintenance being completed per manufacturer’s recommended schedules and thus improved reliability to UTSA.

Recent annual maintenance discovered an insulation bushing requiring replacement on one of the transformers. CPS was able to leave that transformer de-energized for an additional day after maintenance checks to complete replacement of the bushing with no impact to UTSA Main Campus operations, returning the system back to service in an improved condition.

Facilities Operations & Maintenance electrical staff coordinate monthly, quarterly and annual transformer maintenance work with CPS, including any repairs that may require de-energizing a UTSA dedicated transformer unit. Redundant transformers, double-ended switchgear, loop distribution, and licensed Facilities electrical personnel’s knowledgeable of the electrical system all contribute to UTSA’s Main Campus reliable electrical power supply; an essential requirement for high-level research facilities.