Keeping Current: IEEE Standards
by Bob Beckwith, CEO
Beckwith Electric Co., Inc. was formed in 1967 with our first major product,
the M-0026 followed by the M-0067 LTC controls. These controls were designed
with a temperature range of -40 to +80oC. In 1970, the first sale of the
M-0067 was to Federal Pioneer Electric of Winnipeg, Manitoba, Canada,
where -40oC is common during the winter. It is well known that tapchanger
controls are regularly mounted in outdoor cabinets on the side of load
tapchanging power transformers. The temperature inside these cabinets
can reach +80oC in many southern locations in the summertime. Thanks in
part to their temperature durability, sale of the M-0067 still continues
today after 34 years! Who out there can match that record?
Early AIEE standards for protective relays once included a temperature
range of 0-40ºC to cover electromechanical protective relays and
controls. Design technology at the time simply did not support a wider
range. Starting in 1975, various transient voltage tests were added to
accommodate the need for solid-state circuits to withstand these transients.
Later, ANSI/IEEE Standard C37.90 established a temperature range of -20oC
to +55oC for all relays and relay systems.
There exists a phenomenon known as "cold start." This exists
in cold climates where prolonged blackouts are possible due to ice storms.
After a power transformer is without power for 24 hours or more, the oil
may congeal so that it may not flow freely to cool the transformer during
the first few minutes of power inrush. Modern transformer oil has a pour
point of -40 degrees centigrade. Catastrophic failure of the transformer
can occur during this period due to the formation of hotspots created
by the lack of oil circulation. Properly operating protection devices
are critical under these circumstances.
Substation automation must return to service in an operating condition
in spite of extreme temperatures. Protective relays and associated devices
must work, since the probability of their need is high during a cold start-up.
A similar phenomenon occurs in warmer climates when power is interrupted
for even a short time during peak power demand. When power is restored,
load diversification is lost and all air conditioners will have recycled
to the "on" condition producing a peak power demand likely to
extend the blackout. All of the protection and control equipment is expected
to perform correctly regardless of the high temperatures encountered.
Much of the successful performance of today's electric utility protection
and control equipment can be attributed to the strenuous temperature requirements
established by written standards. Not only do the temperature requirements
provide for the obvious advantages but the intrinsic quality of the components
required to meet the temperature standards assure increased reliability
in overall performance. If these requirements are reduced, it is highly
probable that some companies will reduce the quality of their product
in an effort to reduce costs. Companies that continue to produce the high
quality products required by today's standards will be at a definite cost
disadvantage and users will suffer with less overall quality in their
protection and control equipment.
I submitted a negative vote on Draft 14 of C37.90 Standard for Relays
and Relay Systems for the reasons given above. This draft allows temperature
ranges to be defined by the equipment manufacturers. An IEEE standard,
not the equipment manufacturers, is expected to define minimum requirements.
The IEEE should carefully consider the liabilities associated with the
issuance of a standard that may not adequately protect companies that
are responsible for the generation, transmission and distribution of electric
power. Such companies might suffer damage should they purchase critical
equipment under the standard in its present form.
Keeping Current is an editorial column by Bob Beckwith,
CEO of Beckwith Electric. Reproduction of the whole or
any part of the contents without written permission is prohibited.
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