REASON FOR FAST RUNNING OF ELECTRIC METERS
- Why bills of electric consumption suddenly increased when electromechanical meters replaced with electronic meters?
SUDHIR KUMAR SRIVASTAV
AGM-RAPDRP
NTPC LIMITED, NEW DELHI
Abstract -This paper gives an insight into the various aspects on inflated billing of electric consumption for single phase consumers whose electromechanical meters are replaced with electronic meters. This may be very useful for all single phase consumers whose electricity bills are seems to be higher than actual consumption.
I INTRODUCTION
Power Distribution utilities in India is facing a lot of challenges like theft of energy, improper billing, outdated technologies, poor maintenance, financial constraints etc leading to very poor financial health of the sector.
Distribution utilities have acted promptly on theft of energy & improper billing, through replacement of electromechanical meters with electronic meters. Main reasons for replacement of electromechanical meters with electronic meters are:
1. Electromechanical meters, which were installed a few years ago, had started running slow due to moving components in the meter getting worn out.
2. The electromechanical meters, with the passage of time and also by virtue of their design, did not record energy if load is very small.
3. No measuring element was used in return circuit i.e. neutral wire in electromechanical meters. Tampering was easily possible in such meters e.g. reverse phase running, etc. (Detail described below with Figure-1 & Figure-2)
II SALIENT FEATURES OF Electronic meters:
1. Small energy consumption by virtue of indicating lights, LEDs on switch boards, leakage of current due to old house wiring etc., gets recorded by highly sensitive and more accurate electronic meters.
2. Some equipments e.g. TVs, DVDs, etc. when switched off through remote controls continue to consume energy unless they are switched off from the switch mounted on the equipment itself. These types of consumed energy are also recorded with electronic meters.
3. Electronic meters are accurate and sensitive without any moving part. So sluggishness of meters were ruled out & new meters have started recording the actual energy consumption
4. As no measuring element was used in return circuit i.e. neutral wire in electromechanical meters, tampering was easily possible in such meters e.g. reverse phase running, etc. In a tampered meter, it is possible to run the meter as and when required with simple operation of a toggle switch. To deal with tampering problems, a need was felt to have a meter, which has measuring element in neutral circuit also. So important additional design features have been incorporated in the present electronic meters i.e. measurement of current in neutral/return circuit in additional to phase circuit & measurement of higher of the two currents (one measured by measuring element in phase circuit and other by measuring element in neutral circuit.) for computation of energy consumption.
III CAUSE OF INFLATED BILLING:
Feature of electronic meters as mentioned at point 1,2 & 3 above are providing more accurate. It is true that because of above reason there would be marginal increase in the electricity bills generated by new electronic meters as compared with old electromechanical meters. There is a feeling that the bills are inflated but it is only psychological.
But the feature of electronic meters as mentioned at point no.4 are a matter of concern and energy consumption recorded by electronic meter may be highly inflated, if neutral circuit of the household in not isolated properly.
Typical circuit of electromechanical meter is as below:
Here measuring element is used in phase circuit only. So tempering is easily possible by reversing the phase circuit as mentioned in Figure-2. If phase supply is connected to neutral of meter, neutral of meter is connected to load & other point of load is earthed, proper voltage will applied across load & all electrical apparatus will be powered on, but consumption will be NIL, as current is not flowing through measuring coil.
So, to overcome this deficiency & to enable the utilities to trap the fraudulent consumers and to raise more accurate bills for the energy consumed by its consumers, the following important additional design features have been incorporated in the present electronic meters:
a) Measurement of current in neutral/return circuit in additional to phase circuit.
b) Measurement of higher of the two currents (one measured by measuring element in phase circuit and other by measuring element in neutral circuit.)
In electronic meter, if neutral circuit of any house is mixed/connected with any other house, there is possibility of highly inflated bill as described below:
Suppose you are HOUSE-2 & your all connection are perfectly alright, but your neutral is connected with neutral of HOUSE-1 and HOUSE-1 has disconnected his neutral with neutral of his meter.
As seen above, if neutral circuit of HOUSE-1 is disconnected with neutral of his meters and the same is connected with neutral of HOUSE-2, following will be the computation of energy in both houses:
FOR HOUSE-1:
Current through phase measuring coil = I2
Current through neutral measuring coil = 0
Highest of the two current = I2
So computation of energy (I^2*r*t) for HOUSE-2 will be OK.
FOR HOUSE-2 (Your House):
Current through phase measuring coil = I1
Current through neutral measuring coil = I1+I2
Highest of the two current = I1+I2
So computation of energy for your house will be highly inflated.
Here actual current through household load = I1
Leakage Current = I2
Current through phase measuring coil = I1+I2
Current through neutral measuring coil = I1
Highest of the two currents = I1+I2
So computation of energy for your house will be inflated
IV HOW TO CHECK & REMOVE THE DEFECTs:
There is a simple check we can perform to find out whether the problem is in the new electronic meter or in the connections or household wiring etc. The current entering the meter through phase wire and coming out of the meter through neutral wire may be got checked from any qualified and experienced electrician. There could be any one of the following three observations:
- Incoming and outgoing current is almost the same. If such is the case, then it may be concluded that connection to the meters are ok.
- Outgoing current through neutral wire of meter is appreciably more than the incoming current through phase wire. If such is the case, then somebody else’s neutral wire has got connected to the neutral wire of your house and it is because of this reason that the meter is running fast. To be doubly sure, the following additional spot checks may be carried out:
- Disconnect the neutral or switch off the MCB if it is installed in the neutral wire (load side). If the meter is still working, it means that there is an improper neutral connection
- Switch off all electrical points in the house (including LEDs and indicating lamps) and check if the meter is working. If yes, then it means that there is an improper neutral connection.
- Outgoing current through neutral wire of meter is less than the incoming current through phase wire. If such is the case then it means that there is some leakage of current, earthing, etc in the building. This may be because of the old worn-out wiring in the house. To be doubly sure, following additional spot check may be carried out:
- Disconnect all your electrical gadgets in the house (including small indicating lamps) and see if the meter is working. If yes, then it means that some leakage of current is taking place in the building (see question 6 for details with regard to effect of leakage current on billing).
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