:: Intellitech ::

New medium voltage distribution systems shall typically utilize a looped-primary circuit served from a single source, with switching installed to provide a means of isolating a failed cable section while providing power to all loads in the loop. All medium voltage circuits shall be routed in a “daisy chain” manner from the headend switchgear to multiple buildings, and back to the switchgear. The headend switchgear shall utilize draw-out type vacuum breakers. Looped-primary equipment at each building shall typically consist of looped unfused switch cubicles, fused transformer primary disconnect switches, dry-type transformers, secondary meters, and secondary distribution enclosures, all installed indoors in a dedicated electrical room. Consult with ITL for alternate options such as use of liquid-filled transformers, or locating equipment outdoors.

Looped-primary switches at the buildings shall be load break air interrupter switches. Freestanding units are preferred, but in tight situation, wall-mounted units are acceptable. Where possible, the design shall provide for nine feet working clearance in front of the closed switch door. As a minimum, code clearances shall be maintained.

New medium voltage electric rooms shall be isolated, lockable areas with ventilation and adequate openings for installation and removal of equipment. Route of travel for moving equipment through the related building from electric room to exterior shall be provided. No mechanical piping unrelated to the electrical equipment shall be permitted in room. External heat or fire sprinklers are not required in the room. Proper working space and fire ratings to meet code requirements shall be part of the design.

All medium voltage rooms shall contain a ground bus installed completely around the perimeter of the room. Consultant shall provide a detail of this ground bus on the drawings.

Shielded cable shall be used for all above and under ground medium voltage applications (except for jumper cable applications) and shall be contained in conduit or other raceways. It may be used in cable trays in electrical vaults only. Provide a full-size 600-volt insulated copper ground conductor in all conduits and raceways with medium voltage cable.

An independent testing consultant, hired by ITL will perform specialized field testing of medium voltage cabling and equipment.