Florida Regulations 25-6.058: Determination of Average Meter Error
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(1) Average Meter Registration Error for Watthour Registers.
(a) If the metering installation is used to measure a load which has practically constant characteristics, such as a street-lighting load, the meter shall be tested under similar conditions of load and the registration error of the meter “”as found”” shall be considered as the average meter error.
(b) If a single-phase metering installation is used on a varying load, the average registration error shall be determined by one of the following methods. The utility shall select the method that best fits the customer’s usage pattern.
1. The weighted algebraic average of the error at approximately 10 percent and at 100 percent of the rated test amperes for the meter, the latter being given a weight of four times the former;
2. The simple average of the error at approximately 10 percent and at approximately 100 percent of the rated test amperes of the meter, each being given an equal weight; or
3. A single point, when calculating the error of an electronic meter, and the single point is an accurate representation of the error over the load range of the meter.
(c) If a polyphase metering installation is used on a varying load, the average registration error shall be determined by one of the following methods. The utility shall select the method that best fits the customer’s usage pattern.
1. The weighted algebraic average of its error at light load (approximately 10 percent rated test amperes) given a weight of two, its error at heavy load (approximately 100 percent rated test amperes) and 100 percent power factor given a weight of four, and at heavy load (approximately 100 percent rated test amperes) and 50 percent lagging power factor given a weight of one; or
2. A single point, when calculating the error of an electronic meter, and the single point is an accurate representation of the error over the load range of the meter.
(2) Average Meter Registration Error for Demand Registers.
(a) For mechanical or lagged demand meters, registration error shall be determined by testing the meter at both 40 percent and 80 percent of its full-scale value, as read on the reference or standard meter, or as near to these two points as practicable. The following two formulas shall be used to estimate the kilowatt error of the meter at 25 percent of full scale and at 100 percent of full scale:
E25 = [E80 – E40]/[R80 – R40]*[R25 – R40] + E40
E100 = [E80 – E40]/[R80 – R40]*[R100 – R40] + E40
where:
R25 and R100 denote the kilowatt readings on the reference meter at 25 percent and 100 percent of the full scale value of the meter being tested, respectively;
R40 and R80 denote the kilowatt readings on the reference meter at 40 percent and 80 percent of the full scale value of the meter being tested, respectively;
E40 is the difference in kilowatts between the reference reading (R40) and the reading on the meter being tested;
E80 is the difference in kilowatts between the reference reading (R80) and the reading on the meter being tested;
E25 is the estimated kilowatt error corresponding to R25; and
E100 is the estimated kilowatt error corresponding to R100.
The greater of these two estimated kilowatt errors, E25 or E100, shall be expressed as a percentage of the full-scale value of the meter being tested to determine if the meter meets the accuracy requirement of Fl. Admin. Code R. 25-6.052(3)(a)
(b) For electronic demand meters, demand registration need not be separately tested provided the meter has been inspected to contain the correct demand algorithm whenever watthour registration is tested.
Rulemaking Authority Florida Statutes § 366.05(1). Law Implemented 366.05(3) FS. History-New 7-29-69, Formerly 25-6.58, Amended 5-19-97, 7-3-06, 10-27-14.
(b) If a single-phase metering installation is used on a varying load, the average registration error shall be determined by one of the following methods. The utility shall select the method that best fits the customer’s usage pattern.
1. The weighted algebraic average of the error at approximately 10 percent and at 100 percent of the rated test amperes for the meter, the latter being given a weight of four times the former;
2. The simple average of the error at approximately 10 percent and at approximately 100 percent of the rated test amperes of the meter, each being given an equal weight; or
3. A single point, when calculating the error of an electronic meter, and the single point is an accurate representation of the error over the load range of the meter.
(c) If a polyphase metering installation is used on a varying load, the average registration error shall be determined by one of the following methods. The utility shall select the method that best fits the customer’s usage pattern.
1. The weighted algebraic average of its error at light load (approximately 10 percent rated test amperes) given a weight of two, its error at heavy load (approximately 100 percent rated test amperes) and 100 percent power factor given a weight of four, and at heavy load (approximately 100 percent rated test amperes) and 50 percent lagging power factor given a weight of one; or
2. A single point, when calculating the error of an electronic meter, and the single point is an accurate representation of the error over the load range of the meter.
(2) Average Meter Registration Error for Demand Registers.
(a) For mechanical or lagged demand meters, registration error shall be determined by testing the meter at both 40 percent and 80 percent of its full-scale value, as read on the reference or standard meter, or as near to these two points as practicable. The following two formulas shall be used to estimate the kilowatt error of the meter at 25 percent of full scale and at 100 percent of full scale:
E25 = [E80 – E40]/[R80 – R40]*[R25 – R40] + E40
E100 = [E80 – E40]/[R80 – R40]*[R100 – R40] + E40
where:
R25 and R100 denote the kilowatt readings on the reference meter at 25 percent and 100 percent of the full scale value of the meter being tested, respectively;
R40 and R80 denote the kilowatt readings on the reference meter at 40 percent and 80 percent of the full scale value of the meter being tested, respectively;
E40 is the difference in kilowatts between the reference reading (R40) and the reading on the meter being tested;
E80 is the difference in kilowatts between the reference reading (R80) and the reading on the meter being tested;
E25 is the estimated kilowatt error corresponding to R25; and
E100 is the estimated kilowatt error corresponding to R100.
The greater of these two estimated kilowatt errors, E25 or E100, shall be expressed as a percentage of the full-scale value of the meter being tested to determine if the meter meets the accuracy requirement of Fl. Admin. Code R. 25-6.052(3)(a)
(b) For electronic demand meters, demand registration need not be separately tested provided the meter has been inspected to contain the correct demand algorithm whenever watthour registration is tested.
Rulemaking Authority Florida Statutes § 366.05(1). Law Implemented 366.05(3) FS. History-New 7-29-69, Formerly 25-6.58, Amended 5-19-97, 7-3-06, 10-27-14.