With the rapid development of rail transit such as high-speed railway and subway, the structure of its power supply system is becoming more and more complex. with the introduction of advanced technology, there are a large number of nonlinear loads and impact loads. such as rectifier equipment, frequency conversion equipment, high-power electronic equipment and electromagnetic switches and so on. As a result, the technical indexes of the power quality of the power supply system (including harmonics, voltage fluctuation and flicker, unbalance, power factor, etc.) exceed the standard in varying degrees. These power quality problems have caused varying degrees of harm to the power supply system. In serious cases, electrical fire or misoperation or damage of equipment may occur, resulting in serious economic losses and safety risks. Therefore, high-speed rail, subway and other units have very strict requirements on power quality.
When the rail transit line 5 in a certain city is discontinued due to overheating and damage of a station in the capacitor compensation cabinet, the power factor of the power grid is only 0.6-0.7. Through Guangzhou Xuantong Electric's on-line power quality analyzer, it is found that the distribution system contains a large number of harmonics and the current distortion rate is large, and the relevant responsible persons are notified by e-mail and text messages to avoid major power accidents.
Figure 3: distribution electrogram of substation
Figure 2: current waveform before and after treatment
It is of great significance to ensure the safe and efficient operation of the subway distribution system through the monitoring of power quality, especially for the users who have high requirements for power safety. Power quality monitoring has not only achieved huge economic benefits in the transformation of existing lines, but also can optimize system configuration and save a lot of initial construction investment by adding power quality monitoring and management to new subway lines.