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Demand Intervals Used by Various Companies
In order to ascertain the present practice and apparent tendency in this matter, information was secured from the companies operating in the larger cities and which is given in Table II:
General Light Railway
power Buffalo, New York...
2 Min. *Spokane, Washington.
5 Min. New York, New York.
.5 to 10 Min. Cleveland, Ohio...
15 Los Angeles, California..
15 Milwaukee, Wisconsin.
15 Min. *Minneapolis, Minnesota.
15 *Rochester, New York.
15 St. Louis, Missouri.
30 Min. *Boston, Massachusetts.
60 * Brooklyn, New York.
30 *Chicago, Illinois...
60 Min. Kansas City, Missouri.
60 Detroit, Michigan.
60 Philadelphia, Pennsylvania.
The member companies in cities marked thus * use Wright demand indicators for part or all of their D. C. consumers, but not for A. C. consumers. Those marked thus
in one or the other column use either non-instrumental methods for determining the maximum demand; sell on a straight kilowatt hour basis; or else sell no power for railway purposes of any kind.
In some cases a company has used different intervals at different times, but those given in Table II are those reported by them to the writer as being used in their latest contracts for power or wholesale light and power. Arguments in Favor of Thirty Minute Interval
Only two of the companies in the fifteen of the larger cities of the country given in Table II use an interval of less than 15 minutes for general light and power; 6 companies use 15 minutes; 4 use 30 minutes and 1 uses 60 minutes. The writer believes that for the sale of general light power an interval of 5 minutes or less is unwise; also that a 30-minute interval is slightly better than a 15-minute interval and summarizes his reasons as follows:
1. Short interval readings either introduce greater percentage of error in the maximum demand or added complications and difficulty in metering.
2. Short interval readings are not necessary on a large consumer, because his load is usually made up of large number of units and therefore load is more uniform, or to express it differently, the ratio of 5 minutes to 12 hour maxima is small.
3. The existence of a very high or large diversity factor between the small consumers and also between the consumers who use their power intermittently reduces the necessity for a short interval maximum for these small or medium sized consumers.
4. The use of short and frequent intervals requires much more work.to figure and is no inconsiderable item when it is considered that there is usually a subtraction of readings in one form or another and multiplication by a constant.
5. The practicability of off-setting the slight apparent concession of using a longer interval of average of more than one maximum by a slightly higher primary rate of charge per kw eliminates the necessity for use of short intervals.
6. The use of a long interval, say 30 minutes, as against 5 minutes, makes only a very slight difference in income, which may easily be allowed for in rate-making, and promotes much better relations with the consumer who can never understand why he should be penalized for an occasional or accidental demand which lasts only a few moments.
The writer desires that in advocating the use of a maximum of moderate length with a compensated primary charge his position should not be construed as relinquishing the advantage to the supply company of the diversity factor of its various consumers, but rather the opposite, as stated in a former paper, in which he has said:
“The diversity factor is the very foundation rock of centralized energy supply. It is the birthright of the Central Station, the fundamental basis of its existence and its resultant value belongs to the Central Station Company."
Its Definition, Collection
JAMES V. OXTOBY
(Reprinted from Legal Phases of Central Station Rate Making
for Electric Supply, Printed by Association of
Edison Illuminating Companies, 1911)
5-39 40–70 71-90
INDEX TO APPENDIX
Memorandum of Authorities on Reasonable Profit...
U. S. 19....
Extracts from Recent Decisions of Railroad Commission of
Wisconsin, on Reasonable Profit:
tion Company (August, 1909).
sion in matter of gas rates of Charlestown Gas and Elec
tric Company Rule of New York Public Service Commission, Second Dis
trict, as to apportionment of capitalization between
bonds and stock Extract from decision of Massachusetts Gas and Electric
Light Commission in matter of rates of Edison Elec
tric Illuminating Company of Boston. Extract from address of Senator Joseph W. Bailey, on “The
Power to Regulate Transportation Charges by Statutory
state Commerce Commission...
state Commerce Commission..