Indrajit Purkayastha

Effect of harmonics on power measurement

Energy (kWh) measurement has become critically important in determining industrial power flow. With the proliferation of nonlinear loads, there are significant amounts of harmonics in the power distribution system. The effects of nonlinear loads on devices such as circuit breakers have been studied in detail. A review of three-phase power (kW) metering is given, and the effects of harmonics on power measurement are analyzed. It is noted that applying digital microprocessor technology to power metering permits the precise measurement of power. With sample data techniques, it is possible to determine true real power or kWh consumed by the power distribution system or resolve poor power factor questions. >

RMS digital trips offer increased accuracy and reliability advances in low voltage circuit breaker trip technology

The function of low voltage circuit breaker trip units, and the need for direct RMS (root mean square) overcurrent sensing of the sinusoidal and nonsinusoidal current wave, including percentage error analysis are reviewed. It is found that the application of digital microprocessor technology to achieve direct RMS sensing allows the true RMS (heating) protection of thermal-electromechanical trip units, along with the precise protection and coordination selectivity of solid-state trip. This direct RMS sensing provides accurate long-time and short-time overcurrent protection in power distribution systems with the increasing occurrence of nonsinusoidal currents.<<ETX>>