Design Of New Feeder Protection Device For Electrified Railway

Feeder protection device is the most important protection unit in electrified railway traction integrated self-protection system,The power supply arm distance of traction substation is long,and the harmonic content is large when the catenary short-circuit fault occurs,and it is easy to cause the spectrum leakage to produce inter-harmonic,which affects the protection action precision.The fault distance calculated according to the fault data has a large deviation.In this paper,a protection device was studied and developde which can accurately extract fundamental wave data from harmonics,improve the precision of protection action and meet the requirements of fault location.Firstly,the hardware of the device is redesigned.In order to meet the requirements of all power supply modes,the analog quantity collection is increased to the collection of 4 voltage +4 current.In order to improve the high harmonic processing ability,the number of AD sampling points is increased from 24 points to 64 points,and 2～31 harmonics can be accurately extracted.Select an MCU with a main frequency of 120 MHz,and the data calculation is carried out by floating point number method.The whole process of protection judgment processing is shortened from the original 5ms to less than 3ms.Design a separate core board,responsible for data storage and communication,the article 64 fault wave record and message event,1024 event record store target,met the two 100/10 m adaptive and optical/electrical optional demands for communication on design,solve the field only 100 m network or optical fiber communication not compatible.In the design of relay board,the tripping monitoring circuit and the control circuit are separated,which solves the problem of misjudging the field tripping monitoring signal.Secondly,the protection algorithm and ranging algorithm and other software functions are studied and improved.In order to solve the problems of large harmonic content and large error of fault distance calculated by the device due to the inter-harmonic caused by the spectrum leakage,not only the hardware is improved,but also the principle of sectional ranging is improved,and the TLS-ESPRIT algorithm is studied to extract the fundamental wave components for ranging calculation.In order to filter the transient DC component in the early stage of the fault better,the half-wave Fourier and the difference Fourier are combined in the protection calculation.In order to solve the problem of misoperation of protection caused by electromagnetic compatibility interference such as surge and oscillating wave during debugging,the identification of sudden change and the odd-even difference method are studied.The system error of the original network timing method is usually more than 100 ms,but the SNTP and IRIG-B code timing method added in this paper can reach within 2ms.Finally,the model of the new feeder protection device is defined as DPR-LP(T).Prototype test current instantaneous fault export 24 time when ms,the second harmonic atresia and higher harmonic suppression of the adaptive distance protection element action within 0.1 Ω precision.Each circuit has passed the highest level of EMC tests for fast transient,surge and oscillating waves.Fault messages and Comtrade format recordings are stored as files,and all data can be viewed via a touch screen or web page.When the short-circuit fault has inter-harmonics,the error of the Fourier algorithm used in the original device to extract the fundamental wave and carry out the electrical reactance method reaches 1.77 km,and the error calculated by TLS-ESPRIT algorithm is within 200 m.The new feeder protection device not only meets the development needs of the current electrified railway,but also solves the problem of the large deviation of the distance measurement by the electric reaction method.