An electricity meter, electric meter, electrical meter, or energy meter is a device that measures the amount of electric energy consumed by a residence, a business, or an electrically powered device.
ECG uses energy meters installed at customers' premises to measure electric energy delivered to their customers for billing purposes. They are calibrated in billing units (kilowatt hour [kWh]).Meters of different accuracy classes are used for different purposes and applications (e.g. Residential, Non-residential, Industrial, etc.) based on the accuracy requirement. Generally, two broad types of meters are in use in ECG. These are as follows:
WHOLE CURRENT METERS
These meters are connected directly at the entry of the circuit to be measured. They are mostly utilised for Residential and Non-Residential customers with low energy requirements. Broadly, they are classified according to the technology used, and are as follows:
The Electromechanical Meter operates by counting the revolutions of a non-magnetic, but electrically conductive, a metal disc which is made to rotate at a speed proportional to the power passing through the meter. The number of revolutions is thus proportional to the energy usage. The voltage coil consumes a small and relatively constant amount of power, typically around 2 watts which is not registered on the meter. The current coil similarly consumes a small amount of power in proportion to the square of the current flowing through it, typically up to a couple of watts at full load, which is registered on the meter.
The electromechanical meters are all credit meters and are typically:
- Single phase credit meter
- Three phase credit meter
Electromechanical meters are usually of accuracy class 2, i.e., ±2% variation of the nominal value.
Electronic meters display the energy used on an LCD or LED display, and some can also transmit readings to remote places. These meters operate by counting impulses and therefore have ratings of impulses per kWh which differ from manufacturers. In addition to measuring energy used, electronic meters can also record other parameters of the load and supply such as instantaneous and maximum rate of usage demands, voltages, power factor and reactive power used etc. They can also support time-of-day billing, for example, recording the amount of energy used during on-peak and off-peak hours.
These meters are manufactured as either credit or prepaid and may be supplied as follows:
¨ Single phase credit meter
¨ Single phase prepayment meter
¨ Three phase credit meter
¨ Three phase prepayment meter
Electronic meters are generally of accuracy class 1, i.e., ±1% variation of the nominal value.
TRANSFORMER OPERATED METERS
These are meters generally interposed (not connected directly) at the entry of the circuit to be measured. Transformer-operated meters are typically of the three phase category and are utilised for demand above 70kVA (or 100A). Typical customers are SMEs and large non-residential customers such as hotels, restaurants, schools, hospitals, etc. The meters have accuracy classes of 1.0, 0.5 and 0.2 depending on the metering application. They may be either electromechanical or electronic.
The Electromechanical meters are available as either credit or prepaid:
- Three phase CT-operated credit meter
- Three phase CT-operated prepayment meter
The electronic meters are available in ECG as credit type only and typically are used for very large consumption customers.
CT/VT operated electronic meter for 415V, 11kV and 33kV supplies
PROJECTED LIFE SPAN OF METERS
The projected average lifespan of our meters is as follows:
Electromechanical meter – 20 years
Electronic meter – 15 years