Back in the 17^th century, little did Sachem Uncas, chief of the Mohegan tribe, realize that his tribe would grow into a smashing financial success after it opened the Mohegan Sun Casino in the scenic town of Uncasville, Connecticut, U.S., in 1996.

Since then, the casino has grown into a multimillion-dollar organization. With 179,000 sq ft (16,630 sq m) of 24-hour gaming, it has more than 3000 state-of-the-art slot machines, 192 gaming tables and every type of lighting imaginable. It has an electrical load requirement of 10 MW.

The latest addition planned for the Mohegan Sun Casino is the US$1 billion Project Sunburst, scheduled for completion in 2002. It will include a 1200-room hotel (Fig. 1) with a world-class spa and more than 100,000 sq ft (9290 sq m) of meeting and function space; a 115,000-sq-ft (10684-sq-m) Sky Casino; 175,000 sq ft (16,258sq m) of premium shopping; nine additional restaurants and a 10,000-seat arena. When it is completed and operating, the addition is expected to add 25 MW of load.

In preparation for the additional load, the tribe began to strengthen its electric-utility supply system. The Earth Casino, which went on-line earlier, was fed by two 13.2-kV feeders, one from Norwich Public Utility and one from Connecticut Light and Power. They supplied 13.2 kV each to the growing number of buildings. In the mean time, the tribe put in Crow Hill Substation, on Crow Hill Road, near the resort complex (Fig. 2).

A direct tap to a 115-kV transmission line was developed and stepped down to 34.5 kV at Dudley Substation in nearby Norwich. Then, at newly created and close-by Crow Hill Substation, two 40-MVA transformers each step down the voltage from 34.5 kV to 13.2 kV. Thus, all the submersible switches and other distribution in the facility are 13.2 kV. Each of the seven breakers at Crow Hill Substation have a 15-kV automatic transfer switch. Three of the outgoing feeder positions are connected to one of the 13.2-kV sources, while four are connected to the other. Thus, if there is a power outage on the four-switch feeder, the three-switch connection will be backed up, and vice versa.

Right now, the system has three incoming lines, two main power transformers and seven outgoing feeders. The whole Crow Hill Road Substation is tied together with a Powell Electric power control room (PCR) (Figs. 3 and 4). The PCR consists of four large steel rooms that bolt together. One side has the 34-kV switchgear and the other side has the 13.2-kV switchgear.

Load in addition to the Sun Casino building includes the Tribal Utility Authority administration building, the utilities office, the government center, and the newer podium and tower. Another load is the 24-hour Mohegan Sun CITGO gas station that features 20 full-service and self-serve pumps. Currently, seven of these buildings are supplied by 13.2-kV underground feeders, and two more feeders are planned.

The largest of these buildings, the newer Sun Casino, for example, is supplied via underground conduit by its two 13.2-kV feeders, the 750 mcm copper cable with 133% EPR insulation jacketed with PVC. The cables terminate in the casino vault on a submersible SF₆ power switch (Fig. 5) that connects the 13.2-kV cables to the two load-center transformers that step down the voltage to 480 V. The load center transformers supply a number of unit substations within the building that supply 480 V and 120/208 V to the local loads in the complex. They each have a main breaker followed by a tie switch. Thus, if one feeder fails, the tie switch can connect the load to the other.

Submersible Switches Take Over

The submersible switch, the smallest physical size of its type on the market, was acquired from Canada Power Products Corp. (Mississauga, Ontario, Canada). Known as the PufferPak, the 600-A continuous rated switch features compact sealed, corrosion resistant construction suited for indoor, outdoor or vault applications. Switch components are contained in a welded 304L stainless-steel tank factory filled with SF₆ gas. This switch can be mounted on floor, wall or ceiling. In the Mohegan manholes, these switches are bolted to the wall.

In addition, Canada Power Products supplied the switches with stands. Earlier, the electrical contractor field-fabricated the stands.

The heaviest loads — such as the hotel, the arena and the banking center — individually require a single feeder with full distribution and emergency generation backup. There is a second feeder for additional backup to the Sun Casino.

Today's power system has one 13.2-kV feeder coming out of the substation. It goes to a three-way SF₆ switch, one terminal of which picks up the transformer for the booster pump station and the Tribal Utility Authority (Fig. 6). It goes down to Crow Hill Road and goes into another three-way SF₆ switch that currently has one spare position for a planned day care. The third position of the switch goes up Crow Hill Road to another SF₆ switch, which goes up Warehouse Road to another SF₆ switch, which connects to the warehouse transformer.

Peripheral loads can go to 23 MW. The tribe is looking at an ideal feeder loading of about 10 MW. Therefore, it has the ability to expand without having to take power outages, and maintenance and new installations will not affect other loads.

Fuel Cells Coming

The Mohegan Nation Utility has two fuel cells that are to be put in at year-end. Initial capacity is 400 kW and the build-out for the first installation is 1.2 MW. Ultimate build-out for the site would be 3- to 4-MW on-site fuel cells. Heat from the fuel cells will go right into the central plant boiler room. There also are discussions for a possible laundry building and agriculture building, both of which are premier candidates for more fuel cells.

Currently, 52 retail sales outlets are being established in the hotel and convention center areas. Those with gas, electric and water heaters will have their meters tied together with a fiber-optic system.

Future Expansion

The size of this distribution system is equal to that of most smaller towns. Ultimately, the load will be about 50 MW. The SF₆ switches are opening the possibility for peripheral loads and expansion.

In the future, expect another substation, Fort Hill, as well as several more underground feeders. In addition, the 34.5-kV line from Dudley Street Substation will be used as an additional supply feed.

Joseph Cristino is head of Cristino Associates Inc., Electrical Engineers (Redding, Connecticut), which he formed in 1983. He has the BS degree from the University of Bridgeport. His current responsibilities include design and integration of the Mohegan electrical supplies. He is a member of IEEE, NAFE and NFPA. Cristino is a registered professional engineer in Connecticut, Massachusetts, Maine and New York.

Paul Woronik is an engineer with the Mohegan Tribal Authority (Uncasville, Connecticut, U.S.), which he joined in 2000. He has the BS degree from the University of New Haven. His current responsibilities include engineering operations and project management of existing and construction facilities. He is a member of the IEEE Power Engineering Society.