Research On Measurement Method And Safety Warning System Design Of Power Frequency Electric Field

The electric field is an important electrical parameter characterizing status oftransmission lines and power devices, by some theoretical studies and experimentalverification, the electric field measurement technique can be used as an auxiliaryanalysis tool for transmission line fault condition diagnosis and determining safedistance in live working. It will provide strong data support to transmission lines statediagnosis, electrical equipment insulation condition assessment, power systemelectromagnetic compatibility, electromagnetic environment assessment and otherstudies by real-time and accurately measuring electric field. It has great significance forinvestigating electric field effects to the long-term health of workers, protectingpersonal safety of people in high-strength electric field environment, studying onnon-contact measurement, ensuring the safe and stable operation of power systems, andso on.It is deduced the mathematical principle of measuring one-dimensional alternatingelectric field using spherical sensor. The electric field distortion when sensor isintroduction to the field is discussed, and a solution for reducing measurement errorcaused by sensor is proposed; a rational calculation model of power frequency electricfield under high voltage transmission line is established, distribution of electric fieldwhen line is phase loss and abnormal is simulated, and the ccorresponding referencedata is got. Theoretical method for estimating the state of the transmission line based onelectric field distribution law before and after the transmission line fault is proposed; Itis introduced the importance of determining safe distance and analyzed the feasibility ofthe electric field characterizing safe distance when live working,the defects of existingtheoretical and technique methods for determining safety distance is discussed, and anew idea for determining safe distance based on electric field over limit is proposed, thecritical electric fields for transmission lines with different voltage levels in safe distanceis calculated by simulation.It is analyzed and verified the feasibility of measuring the electric field flat platecapacitance sensor and completed sensor design. The flat capacitance sensor is used tomeasure electric field instead of ball sensor. According to the specific needs of eachmodule, hardware design of the system is completed by selecting appropriatecomponents, and software debugging of the system is completed according to measurements need, the overall design of the portable high-voltage power frequencyelectric field measurement and caution apparatus with C8051F410MCU as the core isfinished; Sensor is calibrated in power frequency electric field, The comparisonmeasurement and calibration experiment between homemade instrument and foreignelectromagnetic field measurement instrument is proceeded; the effect on measuringelectric field with human existence is analyzed, and the enhanced factors is introducedto correcting for measurement error caused by the human body during data processing.The test results show that the flat plate electric field sensors can use to measurepower frequency electric field, the scale factor under power frequency electric field is18kV m1mV1, and the measurement system is able to measure power frequencyelectric field around power lines accurately and finish the warning function whenelectric field is over limit, measurement data relative errors are about10%.The wholesystem has good measurement performance. The measurement results have highcorrelation compared with the foreign instrument, so it can meet the needs ofengineering measurement.