IEEE Power & Energy Magazine - May/June 2016 - 84

two complete sets of these self-pressure-generating interrupters. Two separate plain-break contacts provided
additional voltage insulation. A 46-kV
recloser based on this design used a
single set of the self-pressure-generating and interrupting contacts and had
an interrupting rating of 250 MVA.
These were installed on the Consumers Power system in 1957.

The High-Power
Commercial Design
Evolves
The features listed by the task force
imposed criteria that shaped the ultimate design. For example, during the
initial stages in the interrupter design,
the puffer interrupter was a viable
concept. However, the fail-safe design
criteria dictated spring opening, which
imposed practical energy limitations
for operating a puffer interrupter.
The alternative was to design an entirely new mechanism. Given the time

constraints, this was not acceptable,
and the initial interrupter design would
be similar to air-blast designs using gas
stored under pressure.
In late 1958, the SF6 Development
Section, under the direction of R.E.
Friedrich, was formed in the Westinghouse Power Circuit Breaker Division,
and the original engineers were R.N.
Yeckley, mechanical design and verification; R.G. Colclaser, Jr., High Power
Laboratory testing and interrupter design; C.F. Sonnenberg, high-voltage
testing and bushing design; and W.T.
Parker, customer orders.
Under Yeckley's direction, a porcelain-clad prototype of a single twopressure interrupter (see Figure 1) was
tested in the High Power Laboratory to
provide verification of interrupter performance. The operation of the interrupter blast valve was controlled by a
mechanically operated pilot valve. The
design of the interrupter contacts and
Teflon nozzle (see Figure 2) was based

on the previous experience with the
prototype puffer interrupter. Symmetrical currents up to 40 kA were interrupted with this device. Based on the
success of this two-pressure prototype
model, a dead-tank, 230-kV breaker
was to be the first design because of interest at this voltage by the Pennsylvania Power & Light Company (PP&L).
Many decisions were required as
this ground-breaking design evolved.
The major question was the number of
interrupting breaks per phase. A typical oil breaker at 230 kV used up to
six breaks in series per phase. The initial 230-kV SF6 breaker design would
use an interrupter consisting of three
breaks, and the 138-kV breaker, being designed in parallel, would use two
breaks. The minimum number of proposed breaks for each design was limited by the test laboratory capability.
The line-to-ground voltage at 230 kV
is about 132 kV, and the High Power
Laboratory at the time was capable of

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Table of Contents for the Digital Edition of IEEE Power & Energy Magazine - May/June 2016