An Electronic Energy Meter (EEM) functionally outperforms the traditional Ferrari’s wheel
meter. One important advantage of EEM is that in non linear loads, its metering is highly
accurate and electronic measurement is more robust than that of the conventional mechanical
meters. The Power companies benefits from EEM in three significant ways
1. It reduces the cost of theft and corruption on electricity distribution network with
electronic designs and prepayment interfaces.
2. Electronic energy meter measures current in both Phase and Neutral lines and
calculate power consumption based on the larger of the two currents.
3. EEM improves the cost and quality of electricity distribution.
How EEM Works?
The conventional mechanical energy meter is based on the phenomenon of “Magnetic
Induction”. It has a rotating aluminium Wheel called Ferriwheel and many toothed
wheels. Based on the flow of current, the Ferriwheel rotates which makes rotation of
other wheels. This will be converted into corresponding measurements in the display
section. Since many mechanical parts are involved, mechanical defects and breakdown
are common. More over chances of manipulation and current theft will be higher.
Electronic Energy Meter is based on Digital Micro Technology (DMT) and uses no
moving parts. So the EEM is known as “Static Energy Meter” In EEM the accurate
functioning is controlled by a specially designed IC called ASIC (Application Specified
Integrated Circuit). ASIC is constructed only for specific applications using Embedded
System Technology. Similar ASIC are now used in Washing Machines, Air Conditioners,
Automobiles, Digital Camera etc. In addition to ASIC, analogue circuits, Voltage
transformer, Current transformer etc are also present in EEM to “Sample” current and
voltage. The ‘Input Data’ (Voltage) is compared with a programmed “Reference Data’
(Voltage) and finally a ‘Voltage Rate’ will be given to the output. This output is then
converted into ‘Digital Data’ by the AD Converters (Analogue- Digital converter) present
in the ASIC. The Digital Data is then converted into an “Average Value”. Average Value
/ Mean Value is the measuring unit of power. The output of ASIC is available as
“Pulses” indicated by the LED (Light Emitting Diode) placed on the front panel of EEM.
These pulses are equal to Average Kilo Watt Hour (kWh / unit). Different ASIC with
various kWh are used in different makes of EEMs. But usually 800 to 3600 pulses / kWh
generating ASIC s are used in EEMs. Most of the EEMs installed by KSEB have out
pulses of 3200 / kWh. The output of ASIC is sufficient to drive a Stepper Motor to give
display through the rotation of digits embossed wheels. The output pulses are indicated
through LED. The ASIC are manufactured by Analogue Device Company. ADE 7757 IC
is generally used in many countries to make EEMs. ADE 7555 / 7755 ASIC maintains
the international standard CLASS I IEC 687/ 1036.
Front Panel Display( LED type ) of EEM
On the front panel of EEM there will be 4 LED indications
Ǿ N
OK
LED ON
Phase and Neutral OK
E/L
Imp / kWh
LED OFF
Earthing correct
LED ON
Earth leakage and current loss
LED Blinks
Impulses per Kilo Watt Hour.
This LED is larger one.
Impulse rate will be between
800 and 3600 in different EEMs
How to Monitor the Electronic Energy Meter?
1. The first step to monitor the energy meter is counting of the LED pulses per unit (kWh).
Usually the pulse rate will be 800 to 3600 imp/ kWh. Imp.3200 is the pulse rate of most
EEMs used by KSEB. The pulse rate can be calculated by counting the blinking of LED.
2. Suppose the pulse rate is “X imp. / KWh”. (In most meters it is 3200 imp. / KWh). This
indicates the pulse rate of LED if 1000 Watts / second is consumed in 1 hour.
3. Suppose a 100 watt bulb is switched on for 1 minute, the pulse rate will be “P”.
4. Then “P” can be calculated using the formula
P= X x100x60 / 1000x3600
That is if 1000 watts is consumed for 3600 seconds the output pulse will be “X” per hour. So the
pulse rate for 100 watts for 60 seconds is “P”.
So “P” (100 watt per minute) can be calculated as follows:P= X x 100 x 60 / 1000 x 3600
That is 3200(X) x 100 x 60 / 1000 x 3600 = 5.3 pulses / minute
Normally if a 100 watts bulb burns for 1 minute, the pulse rate of LED will be 5.3 blinks per
minute. + or – 5 times can be considered as normal. If the blinking rate is very high, your EEM is
showing a wrong reading and you are forced to pay more.
Get ready to check your EEM
1.
2.
3.
4.
5.
Connect a 100 watt bulb in an outlet holder.
Switch off all the lights, fans and unplug all the electric appliances.
Check the meter. If the LED blinks, it indicates wiring defects and leakage.
Check the wiring and rectify the defect.
If the LED remains OFF, wiring is OK and meter is not sensing the current flow.
6. Switch on the 100 W bulb with the help of another person and count the LED blinks for 1
minute. + or – 5 times can be ignored.
7. Take the total count per minute. It is the pulse rate for a 100 watt bulb/ minute( “P”)
8. If “P” is very high or low (for a 3200 kWh meter) than the “P” already calculated as
above, the meter is defective.
9. Report the matter to the Power company for meter observation.
Know your home appliances; they are hungry.
Most of the electric appliances consume large amount of current. If these instruments are kept
ON for many hours, your electricity bill will be really shocking. The following chart will show
you the power consumption of household electric appliances in One Hour.
Power rating of Household appliances
Appliance
Power rating( in Watts)
Standard
Compact Fluorescent Lamp ( CFL) 8,11,18,35
Bulb
25,40,60,100
Fluorescent Lamp
20,40
Fan
25-80
TV
80-400
Fridge
200-300
Heater
1000-3000
Vacuum cleaner
150-400
Mixi
300-600
Washing Machine
800-1000
Microwave Oven
600-1500
Table Fan
10-25
Computer
80-150
Laptop
20-50
Laser Printer
1000-1500
Ink Jet Printer
25-50
Electric Iron
450-1000
DVD
20-50
A/C 1HP
1000-1500
Water Pump ½ HP
500-1000
Hair Dryer
1200-1500
Music system
20-40
Current consumption
in 1 Hour (in Amps)
0.03,0.040,0.078,0.15
0.11,0.17,0.26,0.43
0.01,0.2
0.1-0.4
0.4--2
1-1.4
4.5-15
0.7-2
1.4-2.8
4-4.5
2.6-6.5
0.04-0.11
1-1.3
0.09-0.22
4.3-6.5
0.11-0.22
2-3
0.09-0.22
4.3-6.5
2.17-4.3
5.2-6.5
0.09-0.17
The ratings are average. This may change depending on the make
Domestic power supply is 230 volts 50 kHz or 110V 60 Hz in some country. The current
consumption depends on the Wattage of the instrument used. Current consumption can be
calculated using the formula
I = W /V
I is the current in amperes, W is the wattage of instrument and V the 230 volt power supply.
For example a Compact Fluorescent Lamp (CFL) rated 11 watts consumes 0.04 ampere
current in one hour at 230 volts.
Wattage of an instrument can be calculated using the formula
W= V x I
Some tips to make your appliances friendly and to save energy.
1. Check the domestic wiring periodically for leakage and current loss.
2. Install ELCB (Earth Leakage Circuit Breaker) which will immediately disconnect the
power when it senses more than 40 milli ampere current through earth line.
3. Fridge is one of the current hungry appliances. Do not keep the door opened for more than
2 minutes. Do not keep hot food materials inside the fridge. Defrost weekly; otherwise
current consumption will be more.
4. Do not keep TV or Computer in the standby mode for long periods. Switch off
immediately after the use. Even in the standby mode these devices takes 10 watts or more
power
5. Unplug all the instruments which are not using daily.
6. Make all the preparations before switching on the instruments like Washing machine,
Mixi, Iron etc.
7. Use heater or water heater only in extreme cold conditions.
8. Restrict the use of Iron and use one with temperature regulator.
9. Overheating and humming from fans indicate defects which lead to over meter readings.
10. Switch off fans and lights after the use.
11. Do not charge UPS, Inverter or Emergency lamp battery continuously (If there is no cut
off facility). It will consume more current as well as reduce the life of battery. One hour
charging at an interval of two days is sufficient to keep the battery in top condition. Over
charging will heat up the battery and reduce its life along with unnecessary power loss.
12. Keep the plugs and sockets clean to avoid sparking and power loss.
13. Avoid the use of Mixi, Heater, Iron etc during the peak hours from 6 pm to 10 pm.
14. Replace all the bulbs with Fluorescent lamps and low watt CFL
15. Use low wattage CFL lamps or LED Lamps in rooms or places where bright light is not
required.
16. Do not charge Mobile phone daily. Equal charging and discharging will keep the battery in
top condition. Charge the mobile phone only when the charge indicator shows 50%
charge. Over charging will reduce the life of battery.
Remember! Unlike mechanical meter, Electronic energy meter will sense very small
amount of current. Even a glowing indicator lamp in the switch board will cost something.
Electricity billing
Electricity billing is based on the usage of current by the domestic appliances. If a 1000 watts
bulb burns for one hour, 1 unit current is used. Current consumption is calculated using the
formula
Total Watts x 1 hour / 1000
For example, the total wattage of all the electric appliances used is 500 watts, the power
consumption in one hour will be
500 x 1 / 1000 = 0.5 units
If the consumption per hour is 0.5 units and the appliances are used 8 hours per day, then the
power consumption will be 4 units per day and 120 units per month
D.Mohankumar