# Metering Formula Essay

1. Meter Multiplier

Meter Multiplier - the multiplier applied to the register reading to obtain kilowatt-hours. M = Kh X Rr X Rs X CTR X VTR

10,000

Where ;

Kh = watt-hour constant of the meter in watt-hour per revolution

Rr = register ratio = the number of revolutions of the register worm wheel for a revolution of the first dial pointer (right hand).

Rs = gear ratio = the number of revolution of the disk for one revolution of the first point

CTR = current transformer ratio

VTR = voltage transformer ratio

Example #1:

A G.E., three phase, three wire, 120 volts, type VM-63-A, Form 5A, Class 20,

KWh meter indicates Kh of 2.4 at its nameplate and register ratio of 166-2/3 was installed at 13.2 KV wye grounded

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CR = Kh(MUT) X Rev. (MUT)

X V(std)

Kh(std) X No. of Element X V(MUT) where; Kh(MUT), Kh(std) - meter constant of Meter Under Test (MUT) and standard, respectively

Rev.(MUT) - number of rev. of Meter Under Test (MUT)

No. of Element - number of element or stator in used

V(std), V(MUT) - Voltage induced to standard and Meter Under Test

(MUT), respectively

c. Average Accuracy = 70% Full Load + 30% Light Load or = 75% Full Load + 25% Light Load

d. Percent Error = Computed Rev. - Actual Rev. X 100%

Actual Rev. or Percent Error = Computed Rev. - 1 X 100%

Actual Rev.

or

Percent Error = (%A - 1) X 100% where :

%A - Percent Accuracy

Example:

Given : a) Meter - Three phase G.E. meter self-contained, class 200, Form 12S, Kh

28.8 Rr 166-2/3 240 volts, TA 30.

b) Standard - G.E., Type IB-10, Kh 0.6 @120 volt @5 amp tap. ampere tap used 5 and 50.

Determine the accuracy of the meter;

a) Left stator, light load test @ one rev. of the meter disk resulted to 24.05 rev. of the standard.

b) Right stator, light load test @ one rev. of the meter disk resulted to 23.98 rev. of the standard.

c) Series, light load test @ two rev. of the meter resulted to 24.04 rev. of the standard. d) Left stator, full load test @ ten rev. of the meter disk resulted to 24.07 rev. of the standard.

5

e)