Prevent tampering in energy meters

  
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Consumers have been found manipulating their electric meters, causing them to stop, under-register or even bypassing the meter, effectively using power without paying for it. An energy meter is a device that measures the amount of electrical energy supplied to a
Prevent tampering in energy meters - schematic

a meter is the kilowatt hour, which is equal to the amount of energy used by a load of one kilowatt in one hour. Figure 1 shows a system block diagram for a three-phase energy meter. As shown the energy meter hardware includes a power supply, an analog front end, a microcontroller section, and an interface section. The analog front end is the part that interfaces to the high voltage lines. It converts high voltages and high currents to voltages sufficiently small to be measured directly by the ADC (Analog/Digital Converter) of the microcontroller. Voltage measurement is done with a shunt resister (shown as "Load"), while the current measurements require more precise measurement and thus are done by Current Transformer (CT) on all phases along with current measurement on neutral. Meter manufacturers often integrate gain amplifiers in order to amplify voltage as well as current measurements in the range supported by the ADC. The amount of amplification required depends on the ADC resolution as well as the Class accuracy (0. 1, 0. 2. 1. 0 etc. ) required for a three-phase meter. A typical energy meter also requires a Real Time Clock (RTC) for tariff information. The RTC required for a metering application needs to be very accurate (< 5ppm) for Time of Day (TOD), which involves dividing the day, month and year into tariff slots. Higher rates are applied at peak load periods and lower tariff rates at off-peak load periods. The...



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