| As an important electric equipment,medium-voltage switchgear can cause huge loss of financial and material resources once a failure occurs.The measurement result of cable joint surface temperature is the key to judge whether the electrical equipment can be operated safely and reliably.Therefore,it is a very important task to measure the surface temperature of cable joints in real time during the operation of MV switchgear.The existing method of the project is to measure the surface temperature of cable joints by using a strap-type wireless temperature sensor,but this method can only measure the temperature at a point and cannot measure the whole temperature field,so this paper proposes a method to measure the temperature of cable joints by using an infrared camera based on the principle of thermal radiation.Due to the complexity of the measurement experimental environment,the method of temperature measurement using infrared camera has some limitations,mainly in that the measurement results are easily affected by environmental factors,so this paper further investigates the radiation measurement accuracy of infrared imaging system on the basis of in-depth analysis of the principle of infrared radiation measurement and the sources of temperature measurement errors.The main research work of this paper is as follows:(1)The industrial environment in which the medium voltage cabinet cable joints are located is a closed space with small space,while the laboratory environment is more open space,and the two have obvious spatial differences,so the infrared temperature compensation study conducted in the laboratory environment may not be applicable to the industrial environment.To address the differences between the spatial states of laboratory and industrial environment,this paper first investigates the differences in temperature measurement in different spatial states through theoretical analysis,and understands that the main factors affecting temperature measurement in different spatial states are environmental thermal field changes and object emissivity.Then the physical models of the three spatial states are established through temperature field simulation to observe the environmental thermal field changes.Finally,the influence of different spatial states on temperature field measurement is verified through experiments,and a box is made according to the physical parameters of the cable room of the medium voltage cabinet to lay the foundation for subsequent temperature compensation experiments.(2)Since infrared temperature measurement is a non-contact temperature measurement,the temperature measurement results are easily affected by atmospheric transmittance,emissivity,ambient temperature,temperature measurement distance and measurement angle.For the working environment of cable joints,this paper mainly considers the effects of ambient temperature,temperature measurement distance and measurement angle on temperature measurement accuracy.In this paper,we firstly study the single interference factor,use the infrared radiation transmission model to deduce the influence of ambient temperature and temperature measurement angle on temperature measurement accuracy,establish the compensation formula according to the theoretical model,and use the law of energy conservation to deduce the influence of temperature measurement distance on temperature measurement accuracy and obtain the compensation formula according to the experimental data,and finally verify the effectiveness of the compensation formula through experiments,Secondly,the study of multi-interference factors,for the more complex characteristics of the impact of multi-interference factors,this paper proposes a condor search optimization least squares support vector machine algorithm for joint temperature compensation,through different algorithm performance comparison to prove the effectiveness of the algorithm. |
