Abstract:The location of ground faults in railway electric lines in 2 × 5 kV railway power supply systems is a difficult task. In both 1 × 25 kV and transmission power systems it is common practice to use distance protection relays to clear ground faults and localize their positions. However, in the particular case of this 2 × 25 kV system, due to the widespread use of autotransformers, the relation between the distance and the impedance seen by the distance protection relays is not linear and therefore the location is not accurate enough. This paper presents a simple and economical method to identify the subsection between autotransformers and the conductor (catenary or feeder) where the ground fault is happening. This method is based on the comparison of the angle between the current and the voltage of the positive terminal in each autotransformer. Consequently, after the identification of the subsection and the conductor with the ground defect, only the subsection where the ground fault is present will be quickly removed from service, with the minimum effect on rail traffic. This method has been validated through computer simulations and laboratory tests with positive results.

Abstract:Owing to the installation of autotransformers at regular intervals along the line, distance protection relays cannot be used with the aim of locating ground faults in 2 × 25 kV railway power supply systems. The reason is that the ratio between impedance and distance to the fault point is not linear in these electrification systems, unlike in 1 × 25 kV power systems. Therefore, the location of ground faults represents a complicated task in 2 × 25 kV railway power supply systems. Various methods have been used to localize the ground fault position in 2 × 25 kV systems. The method described here allows the location of a ground fault to be economically found in an accurate way in real time, using the modules of the circulating currents in different autotransformers when the ground fault occurs. This method first needs to know the subsection and the conductor (catenary or feeder) with the defect, then localizes the ground fault's position.

Abstract:The location of ground faults in railway electric lines in 2 × 25 kV railway power.The authors would like to apologize for any inconvenience caused to the readers by these changes. OPEN ACCESS

The 2 × 25 kV power supply system is the most frequently used traction rail system to provide the huge power needed by high-speed trains. However, locating the ground fault in this power supply system is more complicated than in other configurations of electrical railway power supply due to the installation of autotransformers throughout the line section. In previous papers, the authors have described a ground fault location method with an insignificant installation cost. The method and, moreover, the location discriminate between whether the ground fault is located between a positive conductor and ground or a negative conductor and ground. The current of the high-speed train influences the accuracy of the location of the ground fault. An additional factor which influences the location method is the existence of an arc resistance between the positive or negative conductor and ground. In this paper, the influence of high-speed train currents and arc resistances are analysed to evaluate the error in the location method. The major conclusion of the paper is that the location method has an acceptable precision even taking into consideration the high-speed train current and arc resistance. The validation of the method has been performed by laboratory tests and computer simulations with satisfactory results.

Nowadays, the most commonly used configuration to supply high-speed trains is 2 × 25 kV power supply system. The location of ground faults in 2 × 25 kV power supply systems is a difficult task, since the use of distance protection relays to localize ground faults positions doesn't work properly as the relation between the distance and the impedance seen by the distance protection relays is not linear and therefore the location is not accurate enough. A new simple and economical method to identify the subsection between autotransformers (ATS) and the conductor (positive or negative) where the ground fault is happening, based on the comparison of the angle between the current and the voltage of the positive terminal in each autotransformer, was developed recently. Consequently, after the identification of the subsection and the conductor with the ground fault, only this subsection where the ground fault is present, will be quickly removed from service, with the minimum effect on rail traffic. The high-speed trains demand a power about 12-16 MW, hence a significant current flow through the conductors of the 2 × 25 kV power system. This paper presents a study about the influence of the current consumed by the high-speed trains on this novel ground fault identification method. The operation of the method is correct even with the high-speed train currents in the section with a ground fault. This fact has been validated through numerous computer simulations, obtaining excellent results.