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#1

# Energy Meter Not reading the demand and consumption

I am the head of a power distribution company, presently on inspection i have noted that energy meter of one of our HT consumers are not reading correctly. The meter is connected on 11 kV side and the demand recorded is 4 kVA and Consumption is only 356 kWH. But on the Lt side we have noted that the consumer is taking 200 A of current in 415 V level. By considering the transformation ratio, HT side current from the reading is around 8 A at 11 kV voltage level. The consumer is running on a 24 hour production basis, the consumption calculated theoretically is as shown below...

Consumption = 8* 11*24*30*Load factor 0.8 = 50688 kWH
Recorded demand= 1.7*11*8 = 149.6

But as on recorded on meter the consumption is as follows...

Consumption = 0.48*800 = 384
Recorded Demand = 0.005*800= 4 kVA

Where 0.48 is the consumption on energy meter for a month and 800 is the multiplication factor (MF= Pt ratio 100 and CT ratio 8)

We have changed the meter for checking the case of faulty meter, but no change in reading is noted with the new meter also. We have noted a lose of around 35000 units in that distribution network and thats the reason for checking the meters.

I request the members a solution for the same and what are the possibilities of this faulty reading?
10-09-2013 12:41 AM
Top #2
Check your instrument transformers and leads. Do not rely on nameplate values only. Test the ratio and the wiring. Also look for shorting screws left in terminal blocks if applicable. We found a \$200,000 US annual billing discrepancy due to an incorrect label from the factory on a set of CT's.
10-09-2013 03:09 AM
Top #3
As well as the points by Cris you need to check the following:-
-Test links are not shorting 1 or more current transformers.
- Is the CT polarity correct?
- Is the VT polarity correct?
- Need to look at the CT design to ensure it is operating in the linear part of the performance curve. If the current is too low the curve is non-linear as well as it the current is too high.
10-09-2013 05:20 AM
Top #4
Sounds like theft of service to me. You need to check every mm of wiring between the metering pts and cts, be especially wary of multi-ratio devices and should replace them with single ratio (non-tapped) devices. In addition to the above, when your inspection is complete, seal the cabinet to ensure that no one bypasses any of your devices.