~e; 50/60 Hz frequency standards
From
brian carroll <human@electronetwork.org>
Date
Mon, 15 Mar 2004 11:32:02 -0600
// could not find anything specific online except for
// 'metering standards' pegging decisions at 1910.
// so went to a book in the cardboard box archives...
// The book focuses on .DE, .UK, and .US systems:
quotes from: Thomas P. Hughes' Networks of Power
Electrification in Western Society, 1880-1930
ISBN: 0-8018-4614-5 (paperback) pp. 127-129
"... Early direct-current stations with franchises covering small
central-city districts merged. Polyphase transmission allowed for
large-area supply, so the alternating-current utilities supplying the
suburbs merged into new organizations with the intention of gaining the
entire urban market. The series of mergers that occurred in America and
Germany, and to a lesser extent in Britain, are documented in numerous
utility histories. (43)
"Agreement about technical standards also contributed to the
resolution of "the battle of the systems" and the establishment of the
polyphase, or universal, system. During the period from 1887 to 1892,
when the struggle was intense, utilities and manufacturers chose
different frequencies. Depending on the particular character of supply
and load, different frequencies had distinct advantages. Therefore a
general agreement about frequency did not come through the
establishment of one frequency's obvious technical superiority over the
others; rather, a spirit of flexibility and compromise among the
various utility interests, and especially among the manufacturers, was
primarily responsible for the agreement. Other important factors were
precedent and successful practice-- e.g. Edison's introduction of 110
and 220 volts for power distribution in the United States.
"These historical circumstances and events ought to be remembered
because later generations often assume the standards necessarily
represent the clear technical superiority of one system over another.
"During the early years of alternating and polyphase currents,
133-1/3, 125, 83-1/3, 66-2/3, 60, 50, 40, 30, and 25 cycles were used.
(44: Benjamin G. Lamme, "The Technical Story of the Frequencies,"
~IEEE~Transactions 37 (1918): 60.) Designers and engineers chose the
frequency that was optimum for the particular set of characteristics
created by the coupling of incandescent lamps, transformers, arc
lighting, induction motors, synchronous converters, or other apparatus.
Because design of this equipment was changing rapidly, however, an
already complex situation became more complicated. In America, the
engineering staff of the Westinghouse Company played a leading role in
dispelling the disorder; they attempted to rationalize production by
standardizing frequency. Freedom to decide on a standard frequency was
constrained by the fact that a large number of Westinghouse-designed
central stations {{powerplants}} were supplying incandescent lamps with
60 cycles, but the die was not cast. The Westinghouse designers took
into account the spread of the slower-rpm, directly coupled (rather
than belt-driven) generators that had first been introduced in Europe.
The slower generator, or alternator, was less complex when designed for
lower frequencies such as 60 cycles because fewer field poles were
needed for them than for higher frequencies such as 133-1/3 cycles. Yet
other designers advocated a high frequency because it reduced
incandescent-lamp flickering. The development of a synchronous
convertor that operated well at 60 cycles encouraged supporters of this
frequency because utilities could couple existing single-phase systems,
direct-current systems, and the polyphase extensions and transmission
networks. This ability to couple the old with the new lessened support
for 40 cycles, a frequency that had been advocated by some because of
its suitability for motors and transmission. Design of unprecedentedly
large equipment for a Niagara Falls installation also shaped the
ultimate decision. George Forbes, chief consulting engineer for the
Niagara site, proposed 16-2/3 cycles, but Westinghouse engineers then
wanted 33-1/2 cycles. The relatively low frequencies were well suited
for power transmission. The midpoint of this particular difference was
25 cycles. By about 1900, Westinghouse, the other manufacturers, and
the utilities were settling for two standards: 25 cycles for
transmission and for large motors, and 60 cycles for the more
general-purpose systems. Introduction of the high-speed turbine as
prime mover accelerated the trend towards 60 cycles because generators
with fewer {{magnetic}} poles could be used than with the slow-moving,
reciprocating steam engines. A Westinghouse engineer who took part in
the technical activity surrounding the frequency question took pains to
point out that the struggle to set standards was not a competition
between manufacturing interests, as was the case with many issues
during "the battle of the systems"; rather, it was an effort by
technical persons to find a means to reinforce an all-embracing,
general system of supply. The battle was indeed over. (45)
"In Germany the decision on a standard frequency may have been less
difficult to reach because AEG... encouraged the use of the
slower-speed, directly coupled generators from which high frequencies,
such as 133-1/3 cycles, were difficult to obtain and because
synchronous convertors, for which low frequencies, such as 25 cycles,
were most suitable, had not been widely adopted. The outcome in Germany
was a standard of 50 cycles.
"The Situation in Britain remained disorderly. The tendency before
World War I was toward variation, not standardization. London led the
trend; by 1914, at least ten different frequencies and a bewildering
assortment of voltages were in use in that city. Reasons for the
variety included the absence of oligopoly in the electrical
manufacturing industry and the prestige and influence of the consulting
engineers. (46) One British manufacturer complained that his
competitors, confident that individualism, not business opportunism,
characterized professional competence, carried individualism in in the
design of equipment to an extreme. Having a highly particularized
design seemed to show that the manufacturer and his designers were
"engaged in a superior branch of applied science, not in an industry,
still less in a trade." (47) R.E.B. Crompton, a small manufacturer and
leading consulting engineer, lamented that the consulting engineers
with their design fads; the municipal governments that employed them
and took pride in having their own ideas about how "switchboards and
other plant . . . should be done"; and the small manufacturers, who
were content to have a small order for individual components, retarded
not only the move for standardization but the overall growth of the
British electrical supply industry. (48) An exception to this rule was
the system of electric supply on the northeastern coast of England,
where Charles H. Merz, consulting engineer, was the primary influence
on the design of a regional system (see pp. 443-50 below). Merz
standardized 40 cycles in the region centered around Newcastle upon
Tyne. His reasoning was logical and systematic, for he took into
account the characteristics of the region. His rationality proved
expensive, however, when after World War I his system had to be
integrated at great cost into an all-British one in which 50 cycles was
the standard frequency. (49)"
pp. 127-129
...(further on .UK) "The year 1926 and establishment of the Grid
brought a dramatic change in the orientation of NESCO and Merz &
McLellen, for they were forced to rethink their plans for regional
electrification in the context of a national network. The most
immediate and difficult problem for NESCO was the change in frequency.
It was an especially vexing problem {{see above}}... After 1926,
ironically, the system's 40-cycle frequency was defined as nonstandard.
The earlier process of integration by means of high-voltage
transmission, centralization of control, and standardization had taken
more than a decade, but with the coming of the Grid, this remarkable
achievement became a 1,400 mile inconsistency.
"The Central Electricity Board decided on the uniform three-phase
50-cycle standard instead of NESCO's 40 cycles because 50 cycles was
the European standard (except in Italy); because most of the existing
British polyphase power plants outside NESCO operated at 50 cycles; and
because British manufacturers wanted a market outside England for the
equipment they would design and supply in quantity for the Grid. (100)
The decision entailed serious consequences, for it involved conversion
of hundreds of turbogenerators, hundreds of thousands of motors, and
almost half a million consumers from other frequencies." {{circa 1926}}
pp. 458-59
(and, for anyone interested in an exploding transformer
.mov see: http://205.243.100.155/frames/longarc.htm )
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