Research On Influence Of HVDC Ground Electrode Current On High-speed Railway Traction Net

When high voltage direct current transmission (HVDC) is running on the way of monopole earth-line, DC through the ground electrode is the rated current of DC system, usually up to several thousand amperes. DC ground current can lead to the ground potential rise near the ground electrode, exacerbate corrosion of underground metal facility, and can through the ground electrode of power grid flow in AC system, cause transformer DC magnetic bias, threat the safe and reliable operation of power grid. Traction network is an important part of the electrified railway, which is responsible for providing power to the train. In recent years, with the increasing HVDC system and high-speed rail system, the problem of DC ground electrode close to high-speed rail line has been difficult to avoid. The influence of ground electrode current on high-speed railway traction network becomes a subject need to research.This paper using HVDC ground electrode and traction network of AT power supply mode as research object. Analyzed the mechanism of the DC current intrude high speed railway traction network, researched on the circulation route of the DC current in traction network, circulation route can be divided into contact wire circuit, positive feeder circuit and track circuit. According to the characteristics of traction network element, established the DC model of each element, and then established the DC model of traction network in a power supply segment. Leaving out track circuit, divided the DC model of traction network into positive feeder circuit and contact wire circuit, positive feeder circuit is not affected by locomotive running; contact wire circuit is affected by locomotive running. According to Maxwell equation, listed the basic equation of electrostatic field, deduced the convergence condition of electric field strength and potential shift vector in medium interface, and illustrated two kinds of boundary value problems of electrostatic field.At last, taking the Qingyuan Yulongling ground electrode in Guangdong and the nearby Qingyuan east power supply segment of Jing-Guang high-speed railway as an example, using ANSYS software calculated the distribution of ground potential, When Yulongling ground electrode flows through the rated current, and figured out the ground potential of ground point in this power supply segment. Using MATLAB software calculated DC current in traction network, the maximum value of up to 16A, analyzed the distribution characteristics and influence factors of DC current. Illustrated the harm of DC magnetic bias, and proposed the method of starting from the two aspects of DC ground electrode and transformer neutral point for reducing DC current in traction network.