Study on Power Quality Problems in Railway Networks and Its Mitigation Using Railway Power Conditioner. (Case Study: Ethiopia-Djibouti Railway Line)
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Date
2021-07
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Addis Ababa University
Abstract
The structure of railway electrification system is a single-phase line, it uses power electronics devices and has a time varying load characteristic. This is a cause for considerable current unbalance, harmonics and variable reactive power consumption. This usually leads to power quality problems affecting the proper operation of the equipment. Because of the train's unique operation and electrification characteristics, power quality has been a major problem in railway networks. Throughout the history of railway electrification, a variety of power conditioning devices have been explored and deployed to traction systems.
This research investigates the power quality problems and tries to explore the Railway Power Conditioner (RPC) for improving the power quality problems. Simulation studies are carried out using the software models of the railway network.
To achieve the research objective, a power quality investigation is done by evaluating and measuring major power quality parameters to confirm the mentioned problems at the Ethiopia-Djibouti railway line. The measured values indicate a very low power factor of 0.2, a maximum current unbalance values of 70% and harmonic distortion of 50% in the traction line and 300% on the neutral auxiliary power supply side. The longest power outage due to over-voltage was 202 hours in January at Adigala substation with a power supply availability of 0.70 p.u in 2020 years.
In order to study, the impact of compensating devices, the system is modeled using actual data of the network and simulated using Matlab/Simulink software. To evaluate the Power quality problems mitigation impact of the RPC, the simulation is conducted with and without the integration of the RPC. The simulation result shows that the negative sequence current index declined to 21.9% from 46.91%, the power factor has been improved to unity from 0.499 and the total harmonic distortion of the source current decreased to 0.7645% from 106.6%.
The Ethiopian Railway Corporation should give attention to these power quality problems and their consequences. In addition, they should take remedial actions for mitigations by using RPC.
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Keywords
Harmonic Distortion, Power Factor, Power Quality, Railway Power Conditioner, Unbalanced Voltage