X2 CLASS CAPACITORS IN SMART METERS
Power utilities continue to roll out smart meters because they save time and money. They do away with the need for someone to make periodic trips to read the meter, and the information power utilities receive based on near real-time consumption patterns helps them to control and produce energy more efficiently.
Smart meters typically use a capacitive power supply; these power supplies require an X2 Class capacitor in series (not parallel as in EMI suppression applications) with the load.
All components within a smart meter must be able to withstand the aggressive environmental conditions, and to withstand them for the life of the meter e.g. 15 years. High humidity and high temperatures are typical, and the X2 Class capacitor encounters the additional rigour of being in constant contact with high AC voltage.
Most X2 Class capacitors are not designed for these conditions and degrade too quickly; the high humidity in particular will damage the metallization of a standard X2 plastic film capacitor, resulting in an unacceptable reduction in capacitance over time. For this reason, an X2 capacitor intended for use in a smart meter requires a special metallization process, and additional potting and filling materials.
The three devices below, two from the Epcos division of TDK and one from KEMET, have been specifically designed for use with these severe environmental conditions in mind.