Glimpse of Energy Meters

Electric meter or energy meter is a device that measures the amount of electrical energy consumed. The most common unit of measurement on the electricity measurement is the kilowatt hour [kWh], which is equal to the amount of energy used by a load of one kilowatt hour over a period of one hour. Energy meter system designed to meet your specific requirements. These meters measure the instantaneous voltage and currents, calculate its product and gives instantaneous power. Each customer has different energy monitoring needs and depending on those we can supply electrical energy metering equipment, gas, water or electrical consumption meters.

Electric utilities use electric meters installed at customer’s premises for billing purpose. They are typically calibrated in billing units, the most common one being in kilowatt hour (kWh). They are usually read once each billing period.

Types of Energy Meter

These may be single phase or three phase meters depending upon the supply utilized by domestic or commercial installation. For small service measurements like domestic customers, these can be directly connected between line and load. But for larger loads, step down current transformers must be placed to isolate energy meters from high currents. Basically three types of energy meters are present.

1. Electro Mechanical Induction Type Energy Meter

It consists of rotating aluminum disc mounted on a spindle between two electro magnets. Speed of rotation of disc is proportional to the power and this power is integrated by the use of counter mechanism and gear trains.

It comprises of two silicon steel laminated electromagnets that are shunt and series magnets. Series magnet carries a coil which is few turns of thick wire connected in series with line. Series magnet produces the flux which is proportional to the current flowing. Whereas shunt magnet carries coil with many turns of thin wire connected across the supply and produces the flux proportional to the voltage. These two fluxes lag by 90 degree due to inductive nature. The interaction of these two fields produce eddy current in the disk, exerting a force, which is proportional to product of instantaneous voltage, current and phase angle between them.

Breaking magnet is a permanent magnet which applies the force opposite to normal disc rotation to move the disc at balanced position and to stop the disc while power is off.
Vertical spindle of the aluminum disc is connected to gear arrangement which records a number, proportional to the number of revolutions of the disc, this gear arrangement sets the number in a series of dials and indicates energy consumption over a time. This type of meter is simple in construction and accuracy is somewhat less due to creeping and other external fields. A major problem with these type of meters is their easy prone to tempering, leading to a requirement of an electrical energy monitoring system. These are very common used in domestic and industrial applications.

Advantages of Electro Mechanical Induction type Energy meter

• No moving iron.
• High torque is to weight ratio.
• The moving element has no electrical contact with the circuit.
• Less affected by stray magnetic field.
• Good Damping.

Disadvantages of Electro Mechanical Induction type Energy Meter

• Without proper compensation measures, a consideration amount of errors are caused in the measurement due to temperature, waveform and frequency change.
• Induction meters can be used only for AC measurements.
• They consume a considerable amount of power.
• They have nonlinear scales.

Application of Electro Mechanical Induction type Energy Meter

Electromechanical induction type energy meters are universally used for energy measurements in homes and industries. Government and energy companies charge customers according to these readings. They are cheap to manufacture and very accurate. With some modification they are being used in measuring electricity going to machines in factories.

2. Electronic Energy Meter

Electronic Energy Meter is based on Digital Micro technology (DMT) and uses no moving parts. So the electronic energy meter is known as Static Energy meter. In Electronic energy meter the accurate functioning is controlled by a specially designed IC Called Application specified integrated circuit (ASIC). ASIC is constructed only for specific applications using embedded system technology.

In addition to ASIC, analogue circuits, voltage transformer, current transformer etc. are also present in Electronic energy meter 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 Analogue-Digital converter presented 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 Analogue-Digital Converter is available in pulses indicated by the Light Emitting Diode (LED) placed on the front panel of Electronic energy meter. These pulses are equal to average Kilo Watt Hour (kwh\unit). Different ASICs with various Kwh are used in different makes of EEMs. 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.

Advantage of Electronic Energy Meter

• Better accuracy.
• Low current performance.
• Low voltage performance.
• Difficult to temper.
• Digital display.

Disadvantage of Electronic Energy Meter

• Incorrect magnitudes of fluxes.
• Incorrect phase angles.
• Change in strength of brake magnet
• Change in disc resistance
• Abnormal friction of moving parts

Application of Electronic Energy Meter

Modern solid state electronic energy meters are recently developed electronic components to measure electrical energy. Measurement accuracy of the electronic meter is about an order of magnitude better than that of a mechanical meter, while power consumption is lower by about two orders of magnitude. The electronic energy meter is also better protection against tampering than its mechanical predecessor, and units for prepaid operation(e.g., card readers) and remote meter reading (e.g., wireless, telephone line, or internet) can easily be included.

3. Smart Energy Meters

it is an advanced metering technology involving placing intelligent Meyers to read, process and feedback the data to customers. It measures energy consumption, remotely switches the supply to customers and remotely controls the maximum electricity consumption. Smart metering system uses the advanced metering infrastructure system technology for better performance. These are capable of communicating in both directions. They can transmit the data to the utilities like energy consumption, parameter values, alarms, etc. and also can receive information from utilities such as automatic meter reading system, reconnected\disconnected instructions, upgrading of meter software’s and other important message. These meters reduces the need to visit while taking or reading monthly bill. Modems are used in these smart meters to facilitate communication systems such as telephone, wireless, fiber cable, power line communications. Another advantage of smart metering is complete avoidance of tampering of energy meter where there is scope of using power in an illegal way.

Advantages of Smart Energy Meters

• Eliminating manual meter readings.
• Monitoring the electrical system more quickly.
• Providing real time data useful for balancing electrical load and reducing power outages.
• Making it possible to use power resources more efficient.
• Avoiding the capital expense of building new power plants.

Disadvantages of Smart Energy Meters

• Transitioning to new technology and processed.
• Managing public reaction and customer acceptance of the new meters.
• Managing and storing vast quantities of metering data.
• Ensuring the security of metering data.

Applications of Smart Energy Meters

Smart energy meter is an important device to manage electricity usage. It collects information of power outage from the appliances and communicates this information to the utility center.

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