Fault Location Method Of Cables Considering The Metal Sheath And Armour Structure

As the main electrical equipment to transmit electric energy in distribution network,power cable has the advantages of small in size,low cost in operation and maintenance and high reliability.However,due to the influence of cable quality and grid construction,cable faults occur to the distribution network sometimes.When a fault occurs,the current in the core of the power cable will increase,and the induced current in the cover layer and armor layer in the outer structure of the cable will also increase obviously,due to the electromagnetic induction effect.Taking the outer structure of the cable into consideration,this paper makes an in-depth study of cable fault locationFirst of all,the structure of cable is analyzed and a model of cable considering the metal sheath and armored structure is built.According to the model,many kinds of fault characteristics are analyzed,and the accurate fault location is realized according to the fault characteristics.In this paper,the cable fault location method considering metal sheath and armored structure is studied according to the following main contents:firstly,according to the characteristics of the outer structure of the cable,its influence on the electromagnetic field of the cable line is analyzed.The cable model is depicted by the series-parallel combination of impedance and capacitance,and the circuit model of five-layer structure is established;the electrical quantity relationship between the head end of the cable and any point in the cable section is derived,based on Kirchhoff’s law;the characteristics of three kinds of asymmetric faults of the cable are analyzed,and the corresponding compound sequence network is established and the loop equation is found and solved,thus the fault location is realized.Next,this paper analyzes a detailed example of the proposed fault location method,including the calculation of cable parameters,the rapid measurement of electrical quantity at the head end of cable and the calculation program of fault distance.Finally,the adaptability of the proposed cable fault location method considering metal sheath and armored structure is analyzed,and the effects on the fault location method,in condition of different fault distance,different fault resistance and different fault grounding modes,are studied.at the same time,this fault location method is compared with other methods.the results show that the proposed method has obvious advantages in accuracy.