Underground Distribution Serves Fair at Seattle

              Underground Distribution Serves Fair;
Seattle City Light builds firmly to serve Fair's 22,600 kva after
meeting difficulties with early load estimates by exhibitors
HERALD GWILYM, Supervising Senior
Engineer, Underground Distribution,
Seattle City Light, Seattle, Wash.
The perfect functioning of all
electric equipment at the April 21
opening of Seattle's Century 21 Exposition was the result of three years
of planning for an unfamiliar load
by Seattle City Light engineers.
First load estimates for the undertaking had a fantastic quality. These
engineers' initial contacts were with
promoters and exhibitors' representatives, who had little understanding
of their own electrical needs.
One large exhibitor asked for "3-
million watts." A check put his
actual requirement at 225 kw.
In other instances, exhibitors
added loads to those first estimated,
and some exhibits were not started
or even announced until six weeks
before opening day. Total connected load finally proved to be
22,600 kva.
Although past years' load diversity studies were an aid in estimating
anticipated load, many commercial
installations were reviewed on the
basis of sq-ft area, connected load,
and actual demand. The initial estimate of an 8,000-kva demand was
raised to 10,000 kva as detailed information became available.
Load checks in the first week of
the Fair's operation disclosed an
actual total of 10,833-kva demand
at 90 pf. Consumption in the exhibit areas was computed at 8 w per
sq ft.
Underground distribution was
planned from the beginning. This
involved new supply lines to the
Fair from the 120,000-kva Broad
Street Substation, a few blocks west
of the 74-acre site, and two 26-kv
feeders passing through to districts
beyond. An underground network
replaced the overhead system in the
20-sq-block area between the Fair
site and the downtown underground
service area.
Seattle City Light's engineers decided to provide 4,160-v service to
the Fair, a decision based on facilities available at Broad Street Substation and the large stock of 4,160-
v subway transformers released
through a cutover to 13.5-kv. Hence
four radial bus-regulated feeders
supply the Fair's distribution system, and a paralleling fifth feeder
can be switched to pick up the load
of any failed feeder.
Such switching is made practicable by load-break disconnecting
oil switches at the outer ends of the
four feeders and primary junction
boxes.  The latter have disconnect-
HYDROELECTRIC POWER is represented at the Seattle Fair     in Washington State.   Consumer products are on display in
by this exhibit which is sponsored by all the electric utilities     nearby General Electric Pavilion
36
June   78,   1962
ELECTRICAL   WORLD