EC-RASP: A new electrical energy static counter based on random signal processing conference topic: IC's for instrumentation and control

This paper concerns the design and development of electrical energy static counter, based on random pulse stream processing. Measurement proceeding, calibration and hardware implementation are checked in a prototype. As a result, a simple low cost measurement system has been obtained. The resulting measures have been compared with the ones obtained using a poly phase commercial analyzer. A maximum 2% error has been achieved. This measurement proceeding is patent pending. I. STATE OF ART Historically the monitoring of electrical energy consumption has been done by various types of induction watt meters. The conventional induction watt meter, with rotating disc and shaft, contains a mechanical register (driven by a gear on the shaft) which continuously displays the total accumulated kilowatt hours consumed. Switch or clutch activable mechanical demand and time of use registers are also used on these meters to display demand and time of use quantities. Electronic registers are in common use today with induction type watt meter, to accumulate pulse data proportional to power consumption. This pulse data is usually provided to the register from an optical pick up or sensor device which senses meter disc rotation. These registers have the advantage that they can perform calculations on accumulated pulse data and electronically display much more information than is possible with conventional mechanical type registers. Nowadays, better performances are required and achieved using static counters. In this sense, electric companies have found it desirable to measure, in addition to total kilowatt-hours, power factor, KVA, or reactive volt amperes. The measurement of reactive volt amperes typically has been accomplished by using a second meter in conjunction with the conventional kilowatt-hour meter. From the reactive volt amperes and the real volt amperes, quantities such as power factor and KVA can be calculated. This second meter for measurement of reactive volt amperes is a watt meter connected with phase shifting transformers in the voltage circuits. It is also interesting to provide the capability to digitally configure the meter to measure electric energy flow in any of the different electrical services. Finally, it is desirable the possibility of connecting to either single phase or poly phase power line systems. All these characteristics should be accomplished by low cost and precise simple devices. Presently, electronic counters and watt meters use either analog circuits, or an analog to digital conversion, followed by a pure digital processing, based on microprocessor systems, micro controller systems or digital signal processor (DSP). In the following, several patents are described. European patent No. 94110967.0 [1] describes a static kWh meter that makes use of an analog multiplier. From the pulse-width modulated voltage, a pulse-width/pulse-height modulated signal, proportional to the power, is generated, using analog connectors. A frequency signal is thus obtained, which is passed through a divider circuit to the counter of the kWh meter for determination of the energy that has been consumed. Analog connectors have a detrimental property, because they produce extra voltage and current pulses in the signal to be measured. So, it is necessary to compensate this effect, including an additional electronic to solve the problem. Besides, typical disadvantages of analog electronic devices are present: noise sensitiveness, thermical sensitiveness, manufacturer tolerances : : : European patent No. 94203283.0 [1] uses a digital signal processor from the analog to digital conversion of voltage and current. High number of performances are achieved at the expenses of a high cost device. In this paper a new static energy counter is presented. That is, a counter in which both current