DESIGN AND IMPLEMENTATION OF A SEMI-INDUSTRIAL PROTOTYPE OF A MICROPROCESSOR BASED MULTI TRANSDUCER

[ Shahkolaey ] - Electric Power Research Center
[ Irani ] - Electric Power Research Center

خلاصه مقاله:

The inspection and control are very important as~ in ail industries specially in electrical industries. Measurement and data gathering and transmitting is one of the major requirements for automation and control of the generation, transmission sion and idstribution network Spectal devices are used for measuring and transmitting quantities such as alternative voltage, current, active and reactive power, frequency and the power factor, among them the two most important are transducers and multitransducers. Introducing these devices, this article deals with the design of a microprocessor based multitransducer Each transducer is responsible for measuring one of the above quantities and generating a de current proportional to it this current then goes to the next stage ( RTU )for transmission. A multitransducer is in fact a combination of some transducers in One Package. generating at it's output some dc currents proportional to thier relative network quantities. the device which this article deals with, samples the voltages of RS and TS and the currents of R and T of the network in a two -watt meters manner. It then computes the required quantities such as the rms voltage of line, the rms currents of each of the three lines , total active and reactive power, total power factor and flequency and generates at it's output six currents s from 4 to20miliAmperes proportional to thier currentsare electrically isolated from each other and from relative quantities. These 6 processing circuitary. Micro Controller 8751 with its valuable capabilities is used for sampling the input usignals. A short discussion of the overall algorithm follows: Syncronized with the network 32 samples are collected from each of the four input signals. After each sampling and saying of the 128 samples, computation leads to the 6 output dc currents. sampling and refteshment ofoutPut signals takes place every 400 miliseconds. output signals are in the form of current sour= and are capable of driving 0 to 500 ohms loads. A prototype of arnultitransducer with the above specification are made and tested and the test results are included in an appendix Due to these tests the maximum measurment error is ± %1 ( class 1 ). 1 he authors are trying to reduce this ; error to ± % 0.5 ( class 0.5 ) ,by ncreasing the accuracy of input measuring transformers, opfirnizing the output isolators and changing D/A and A/D convenors from 8 bits to 12 bits , which yields to mass production of these devices that are severly needed in Iran's electrical industries.