A Study Of Ultrasonic Model And Technology For Detecting Liquid Level In Sealed Boxes

In oil and gas industry,a large number of power control circuits are necessary for monitoring and controlling every links of collection,transfer and processing.Electrical junction boxes play an important role in signal transition and relay between cables.However,due to long-term exposure to the harsh outdoor environment,the sealed electrical junction box will inevitably accumulate internal water.The accumulated water can seriously affect the insulation performance of the wires inside the junction box and increase the risk of short-circuit or even explosion.Therefore,it is necessary to measure the water accumulated inside the junction box in time,so that potential safety hazards can be reduced.In addition,the measurement of water level needs to be performed under a non-intrusive method,since the electrical junction box works in a high-voltage state and cannot be opened during its working time.Based on the ultrasonic impedance method,a specific set of measurement scheme for the liquid level was studied and proposed to fulfill the aforementioned requirements.An ultrasonic transducer model was also developed.Then,the complete ultrasonic measurement system was modelled on the basis of the transducer model and the coupling between the transducer and the box.After that,the characteristics related to the liquid level were summarized and extracted from the established model and a supporting detection algorithm was also developed to detect the water level inside typical junction boxes accurately.It can be concluded from the experimental results that the proposed water level detection technology is capable of detecting the actual water level and provides an efficient method and model reference for the detection of internal water level of the junction box and similar water level detection fields under an industrial environment.The main contents of this thesis work include:(1)Research on the water level detection scheme of the sealed electrical junction box.Conventional ultrasonic liquid level measurement techniques were firstly analyzed and compared.Considering the structure of the sealed electrical junction box and measurement requirements,the technical scheme of detecting the water level in the electrical junction box based on ultrasound was then studied.At last,the corresponding technical scheme framework was established and completed.(2)Modeling of the electroacoustic conversion of ultrasonic transducers.A reasonable type of ultrasonic transducers was selected according to the measurement requirements,and its structural composition was analyzed then.The selected transducer was analyzed and studied in terms of its basic working principles and its typical vibrational characteristics.Based on the former analysis,the electro-acoustic emission and acousto-electric receiving process of the ultrasonic transducer were modelled and studied respectively.The corresponding mathematical expressions of the transducer model were given at the same time.After that,simulation software and ultrasonic experiments were used to verify and analyze the built transducer model.The transducer model can provide a necessary theoretical basis for the subsequent establishment of a complete detection system model.(3)Modelling the ultrasonic detection system of the liquid level inside the sealed electrical junction box.The model composition of the actual ultrasonic liquid level detection system was firstly summarized.Then,the electronic components of the ultrasonic detection system were analyzed.After that,on the basis of aforementioned transducer model and acoustic coupling effects,every step in the detection of the water level inside the junction box was modelled and studied,respectively.Also,the corresponding mathematical expressions were obtained.Similarly,the simulation software and ultrasonic experiments were used to verify the established system model.(4)Study of the liquid level detection method for the sealed junction boxes.The characteristics of the built model were analyzed and information related to the water level was extracted.Using the extracted information,a specific liquid level detection method and the corresponding algorithm were designed and developed so as to detect water accumulation inside the electrical junction box accurately.In this study,the experimental systems for the transducer model and the detection system model were built for verification.The outcome proved the validity and reliability of the models of transducer and the detection system model.An experimental system for the liquid level detection method was also built for verification purpose.The experimental results showed that the proposed ultrasonic detection method in the electrical junction box and its supporting algorithm can accurately detect the water level in acrylic water tanks and two typical types of junction boxes.The maximum error of the experimental results was less than 1mm and the accuracy shows potential for industrial application.