What is the reason for the frequent voltage fluctuation of track circuit in electrified section?

1. Causes of voltage fluctuation and flicker (1) Electrical equipment has impact load or fluctuating load, such as electric arc furnace, steelmaking furnace, rolling mill, electric welding machine, rail transit, electrified railway, short circuit test load, etc. (2) Short-circuit fault occurs in the system, causing power grid fluctuation and flicker. (3) When the system equipment is automatically switched on and off, it will have the influence of operation wave, such as automatic switching of standby power supply and automatic reclosing. (4) Power grid voltage fluctuation caused by lightning strike. 2. The influence of voltage fluctuation and flicker. Voltage flicker is mainly a parameter that represents the subjective feeling of human eyes to lamp flicker. Generally, the switch action or load change is large enough relative to the short-circuit ability of the system. Although some voltage fluctuations are within the normal voltage variation limits, they may cause lights flashing around 10Hz, which will interfere with the normal work of voltage-sensitive electronic equipment and instruments such as computers. Voltage fluctuation and flicker are mostly generated in the distribution system and transmitted to the user power supply terminal on the low voltage side through the distribution transformer. The main reason for voltage fluctuation and flicker is that industrial electrical loads, such as the operation of electric arc furnaces and welding machines and the switching of capacitors, may produce rapid voltage changes. There are similar physical reasons for voltage fluctuation and harmonic generation, such as nonlinear characteristics of impact load, regular or irregular opening and closing operation, etc. Nonlinear AC load current causes grid voltage fluctuation on frequency-dependent grid impedance. The first choice to solve the influence of voltage fluctuation and flicker is to use power electronics technology and fast reactive power compensator to eliminate the flicker of power supply, so as to reduce the components of voltage except power frequency.