IEEE Power & Energy Magazine - July/August 2017 - 94

OIL
Introducing Dry-Type
Series Resonant Test
Sets with low PD
levels for testing MV
cables or generators.

figure 5. A Prime 400 minicomputer with "virtual memory" and a large address space, circa 1975. (Note the evolution in the operator's uniform!) (Photo
used with permission of STFC Rutherford Appleton Laboratory and www.hiltoncomputing.org.uk.)

Rating-30kV 200kVA - Patent Pending

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94

ieee power & energy magazine

highlighting the work of a single company. Readers will understand that
there was explosive development all
over the world. I cannot follow all of the
threads in this short column.
In 1969, power Technologies Incorporated (pTI) was founded by engineers coming out of the ge group. at
the time, there was a strong industry
need for an increased computational
capability to analyze rapidly expanding power systems. For example, hydro expansion in brazil and rapid
coal development in the midwestern
united States were straining available
analytical tools.
Very basic load-flow programs were
in use on a time-sharing service. all
input, output, and user interaction was
done through a ten-character-per-second
teletype on a voice-grade telephone
l i ne. With the introduction of the
Hewlett-packard (Hp) 2120 "minicomputer," simulation tools began to
evolve quickly. The Hp 2120 occupied
a 5-ft, 19-in tall equipment rack and
provided engineers with a grand total
of 32,768 16-b words (64 kb), a 1-mb
permanently mounted disc, and a 1-mb
drive for removable discs.

pTI introduced the first interactive
commercial digital power-flow and
transient stability simulator, pSS/2, on
the Hp 2120. The program's capacity
was 256 buses for power flow and 128
buses for dynamic simulation. There
was resistance from many corporate
IT departments to perceived deviations
from the centralized computing philosophy of the time, and to avoid conflict
many of the Hp-pSS/2 systems were
named "network analysis machines"
rather than computers.
pSS/2 became pSS/e for installation on prime 300 computers handling
networks of up to 1,000 buses. When
the prime 400 minicomputer arrived
in about 1975 (Figure 5) with the introduction of virtual memory and a large
address space, the "lid came off," and
limits were expanded to 4,000 buses.
The prime computers were followed
by DeC VaX-11 systems, and the capacities of pSS/e expanded as memory
prices fell and usable memory grew.
pSS/e had proprietary contemporaries within various utilities and manufacturers. These included the Western
System Coordinating Council program
(which originated in arizona public
july/august 2017



http://www.hilton http://www.org.uk http://www.EHVTEST.COM/dry-type

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IEEE Power & Energy Magazine - July/August 2017 - Cover3
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