Current through Register Vol. 48, No. 3, March 22, 2024
1.
Method of Determining Average Error of Meters.
A. Field testing the average error of a
service watt-hour meter shall be determined as follows: The error at Light
Load, here defined as approximately 10% of the rated capacity (Test Amperes) of
the meter, shall be determined by taking the average of at least two errors
determined from as many separate tests on the same Light Load, which error must
agree within one-half percent (1/2 %).
In the same manner, the error at Full Load, here defined as
approximately the rated capacity (Test Amperes) of the meter, shall be
determined. The average error of the meter shall then be determined by taking
the average error at Light Load plus four times the error at Full Load (Test
Amperes) and dividing this sum by five, proper consideration being taken of the
sign of the two errors.
B.
Meter Shop Testing--When an electronic test board is used, the average error of
a watt-hour meter shall be determined as follows: The error at Light Load, here
defined as approximately 10% of the rated capacity (Test Amperes) of the meter,
shall be determined. The error at Full Load, here defined as approximately the
rated capacity of the meter or Test Amperes, shall be determined. The average
error of the meter shall then be determined by taking the error at Light Load
plus four times the error at Full Load (Test Amperes) and dividing this sum by
five, proper consideration being taken of the sign of the two errors.
2. Meter Accuracy.
A. Creeping: No watt-hour meter which
registers on "no load" when the applied voltage is less than one hundred and
ten (110%) percent of standard service voltage shall be placed in service or
allowed to remain in service.
B.
Initial Accuracy Requirements--No watt-hour meter shall be in service which is
in any way defective to impair its performance, or which has incorrect
constants, or which has not been tested individually or under a sample meter
testing plan approved by the commission for accuracy of measurement and
adjusted, if necessary, to meet these requirements at unity power factor:
Average error not over 0.5% plus or minus;
Error at Full Load (Test Amperes) not over 0.5% plus or
minus;
Error at Light Load not over 1.0% plus or minus.
C. Adjustment After Test--Whenever
a test made by an electrical utility, contract vendor by or on behalf of the
electrical utility or by the ORS on a service watt-hour meter connected in its
permanent position in place of service shows that the average error is greater
than that specified allowed above, the meter shall be adjusted to bring the
average error within the specified initial accuracy limits, or the meter shall
be replaced.
3. Test
Instruments.
Each electrical utility shall own and maintain such standard
watt-hour meters, such instrument transformers, voltmeters, ammeters and such
other instruments necessary in maintaining the accuracy of its standards used
in testing the meters serving its customers.
