Analysis On How Electromagnetic Interference Of Geomagnetic Storms Affect The Railway Track Circuit

Railway track circuit is an important component of the high speed railway signal system. The core device of the system is microelectronic circuit which belongs to the weak electric areas. It is vulnerable to the external electromagnetic interference. Geomagnetic storm is an extreme weather disaster which causes the severe disturbance of the Earth’s magnetic field and results in the Earth Surface Potentials(ESP).ESP and ground together with rail compose a loop. Then geomagnetic induced current (GIC) is produced. If geomagnetic storm invades the track circuit, GIC will threaten the normal operation of the track circuit.This paper explores the reason of the geomagnetic storms and how geomagnetic storms interfere with the choke transformer and track relay in the track circuit. This paper figures out the equivalent model of receiving end of 25Hz phase-sensitive track circuit and choke transformer, using the actual parameters to calculate the terminal voltage of track relay. As a result, when the nonlinear magnetizing inductance decreases from2.3Ω to 0.2Ω, the terminal voltage of track relay decreases about 41%, which will cause the contact of track relay to fall. Then we find out the calculation method of ESP and GIC according to a simulation based on GIC flow path in the track circuit.This paper figures out the one-sending one-receiving four-terminal network equivalent model of the track circuit. The author calculates the electrical parameters of each node within the model when there is no GIC and deduces the relationship between the presence of GIC and the voltage across the track relay.This paper uses Maxwell software to find out how GIC affects the electrical characteristics of choke transformer. We draw several electromagnetic figures of choke transformer including exciting current, induced voltage and flux linkage. The results show that GIC which is 2.5A can make choke transformer DC bias seriously and cause terminal voltage of track relay to decrease, resulting the relay malfunction. Besides, the paper uses Maxwell software to try a simulation of the terminal voltage, the loss and the front contact pressure across track relay. As a result, when there is no train on the railway, asymmetric GIC values of over 1.5 A is enough to make track relay malfunction from the state of picking up to fall down, causing interference of high-speed railway track circuits. The author takes the commonly used WXJ25 type phased sensitive track circuit receivers for example and analyzes the impact to the signal transmission of the track circuit by GIC. The results show that if GIC exists in the track circuit, WXJ25 type phase sensitive track circuit may lead the track circuit relay making error actions. This problem requires a high degree of attention.At last, the paper uses Simulink to figures out the track circuit receiving end physical simulation model to analyze the terminal voltage waveform of track relay. The author introduces some methods to suppress GIC flowing in the high-speed rail electrical system.The aim is to analyze and compare the pros and cons of various methods to weaken and warn the impact of geomagnetic storms on high-speed rail track circuit.