Researches On Multi-function Watt-hour Meter Based On A New Type Of Electronic Current Transducer

At present, the electromagnetic current transducer is commonly used as the current signal picker in electronic multi-function watt-hour meter, but there are some issues existed in the electromagnetic current transducer, such as having iron core, easy to saturation, smaller measurement range and susceptible to external electromagnetic interference and so on. In recent years, the electronic current transducer based on the air core coil has become the hot research spots in the power system. Therefore, for developing new types of electronic watt-hour meter products to meet the application demand of the meters market, making the electronic current transducer based on the air core coil used in energy metering devices will have important theoretical significances and practical application values.This paper proposed a new design of multi-function watt-hour meter based on PCB (Printed Circuit Board) electronic current transducer, mainly discussed the application of the new type of PCB air core coil combining with the energy metering chip ADE7758 in energy measurement, and, designed the hardware circuit and software architecture of the multi-function watt-hour meter. First the structure and principles of the new type of PCB air core coil and electronic current transducer composed of the PCB air core coil and external integrator were analyzed. Based on this, a method for picking up current signal with electronic current transducer which is composed of the PCB air core coil and ADE7758 internal digital integrator was proposed, this approach can effectively increase the accuracy and range of the current conversion, reduce costs. Two kinds of interface circuit between the PCB air core coil and ADE7758 were analyzed, the instrument amplifier in interface circuit adopted bipolar power supply mode, which has simpler circuit, better reliability and stability. Then, according to its function demands, the watt-hour meter's hardware system was divided into the power module, the measurement module, and the MCU (Micro Controller Unit) and its peripheral circuit module, for designing it in detail. MCU chose H8/38327F products having high-performance, ultra-low power consumption. Final the multi-function watt-hour meter's software design was analyzed, the main program managed its various functional modules reasonably and effectively in circular query way. Theoretical analysis and simulation, experimental results show that the new type of PCB electronic current transducer has a good performance, can make up some deficiencies of the electromagnetic current transducer, and suitably apply to the low current (below 100A) measurement systems. While, the multi-function watt-hour meter, which was designed by referring to the DL/T614-2007 standard, can realize various functions, such as time-sharing measurement, maximum demand measurement, RS485 and infrared communication etc., with high measurement accuracy, low power consumption, and strong ability of anti-jamming. So the multi-function watt-hour meter can be applied in practice.