# Interpreting CT Ratio and Calculating Primary Power from meter readings

#### kelvin273c

Joined Apr 12, 2018
1
The Question
How can I interpret CT Ratios and apply it to my data to derive Power readings for a Three Phase Circuit?

Context of the issue
Unfortunately I have no electrical engineering experience; I am merely a Data Analyst and I have been given some meter data from a commercial building and I need to calculate the total energy consumption in kWh from the meter readings
The meter readings are taken at 2 second intervals for a 3 phase circuit. Along with the meter id and timestamp, each row consists of the following fields:
VFN1,VFN2,VFN3,MAXIM1,MAXIM2,MAXIM3,P1,P2,P3,Q1,Q2,Q3,I1,I2,I3. The Units are shown in the screenshot below, so it is clear that:
VFN1 to VFN3 is in volts, which measures potential difference
I1 to I3 is in Amps, which measures the current
P1 to P3 is in kW, which measures the Power
Initially I thought it would suffice to add the Power readings together (i.e. P1 + P2 + P3) to derive total Power for each 2 second interval
I then aggregate the 2 second readings into half-hourly readings and multiply by 0.5 to get a kWh figure. Unfortunately the total consumptions in kWh
are ridiculous when compared to historic annual consumption.

Example Data: The first two examples are taken from the same meter, the third example is taken from a different meter with a different CT Ratio

Example Data 1
CT RATIO: 10:0,01:0,1:1:70A
VFN1: 2354
VFN2: 2356
VFN3: 2369
MAXIM1: 10
MAXIM2: 0
MAXIM3: 0
P1:- 10
P2:- 0
P3:- 0
Q1:- 4
Q2:- 0
Q3:- 0
I1:- 48
I2:- 0
I3:- 0

Example Data 2
CT RATIO: 10:0,01:0,1:1:70A
VFN1: 2336
VFN2: 2346
VFN3: 2357
MAXIM1: 9
MAXIM2: 192
MAXIM3: 0
P1: 8
P2: 426
P3: 0
Q1: 6
Q2: 156
Q3: 0
I1: 47
I2: 1939
I3: 0

Example Data 3
CT RATIO: 100:1:0,1:1:1000A
VFN1: 2350
VFN2: 2359
VFN3: 2371
MAXIM1: 294
MAXIM2: 300
MAXIM3: 274
P1: 294
P2: 304
P3: 274
Q1: 81
Q2: -86
Q3: -91
I1: 130
I2: 134
I3: 122