Indoor unit substations may be required under certain designs. Where used, these shall be three-phase units equipped with a loadbreak fused switches, with current limiting fuses. SF6 gas insulated equipment shall not be used unless approved by Engineering Services.
Taps, two at 2-1/2% and each alone and two at 2-1/2% each below normal shall be provided.
Where indoor transformer rooms are used, they must be adequately ventilated with powered ventilators, dampers, and a suitable control system.
26 12 00 MEDIUM-VOLTAGE TRANSFORMERS
.01 Distribution Transformers
This work is typically installed by PSU Utility Services. Discuss medium voltage pad-mount transformer project requirements with Engineering Services.
Provide transformer foundation for exterior locations. Ground per “Grounding” section below.
Indoor oil-filled transformer, when approved by Engineering Services, shall be FM approved (not just the oil itself). Contact Engineering Services for minimum efficiency requirements.
Where fuses are used, a complete set of spare fuses shall be provided.
Provide complete information, instructions, wiring diagrams and manuals for maintenance and servicing.
.02 Grounding
All electrical systems shall be suitably grounded, including all non-current carrying metallic components of all equipment and metallic conducts. Grounding shall be accomplished as required by the National Electric Code.
Provide minimum 2/0 AWG bare copper ground ring with at least two (2) 96” ground rods around transformer foundation. Exothermically weld rods and ring. Ring shall be a minimum of 24” from the edge of the foundation, buried between 18” and 24” deep. Rods shall be installed at opposite corners or at a distance of more than rod length apart. Extend cabling a minimum of 48” above grade for connection to transformer. Do not connect this ground ring to the building service.