1) Avoid harmonic damage, make sure the safety and reliability of rail transit distribution system
2) Reduce active power consumption of harmonic
3) Safely improve power factor, avoid power factor’s examination penalty from power supply department
4) Make sure the steady operation of intelligent control system and operation system
5) Supply reliable, sustained power for Ventilation system, lighting, elevator devices in station
The harmonic loads of power consumption equipments are complicated in urban rail transit, lighting and other non-wire single-phase loads produce 3times harmonic, superimposed on the neutral line; inverter air conditioner, elevator, UPS, water cooling unit and other equipments produce 5 or 7times harmonic. DC direction rectifier transformer(24 pulse rectifier) produce 23times and 25times high background harmonic and pour into low-voltage 400V power supply system. Harmonic will make cable and transformer heat; also will lead false action of switch and relay protection; high harmonic will effect the normal communication of monitoring system. Besides, as the cable between stations in metro is long and capacitive, in the 400V power supply system, the side normal reactive power compensation will lead to overcompensation of middle voltage side.
From the different function of loads in urban rail transit, there are 2 main loads:
1. Traction loads which is required for electric buses’ operation
2.Power lighting which is used for station, interval, car depot, control center and other buidling, such as ventilator, air conditioner, automatic lift, Escalator, elevator, water pump, lighting, AFC system， FAS, BAS, communication system, signal system.
Main harmonic source in power supply system of urban rail transit is below:
Traction rectifier inverter device produce high harmonic(11times, 13times etc.)
Others are from large nonlinear load of transformer(3times, 5times, 7times)
Harmonic quantities and kinds are increasing with the updated devices and increasing passenger flow.
Leading harmonic is increasing.
As the traction load is installed in 10KV or 35KV side, normally use the 12 pulse wave rectifier device, harmonic content will be reduced; when harmonic content is within standard, can use for the 0.4KV side control harmonic which produced by second electric group.
The harmonic loads of power consumption equipments are complicated in urban rail transit, lighting and other non-wire single-phase loads produce 3times harmonic, superimposed on the neutral line; inverter air conditioner, elevator, UPS, water cooling unit and other equipments produce 5 or 7times harmonic. DC direction rectifier transformer(24 pulse rectifier) produce 23times and 25times high background harmonic and pour into low-voltage 400V power supply system. Harmonic will make cable and transformer heat; also will lead false action of switch and relay protection; high harmonic will effect the normal communication of monitoring system. Besides, as the cable between stations in metro is long and capacitive, in the 400V power supply system, the side normal reactive power compensation will lead to overcompensation of middle voltage side.
From the different function of loads in urban rail transit, there are 2 main loads:
1. Traction loads which is required for electric buses’ operation
2.Power lighting which is used for station, interval, car depot, control center and other buidling, such as ventilator, air conditioner, automatic lift, Escalator, elevator, water pump, lighting, AFC system， FAS, BAS, communication system, signal system.
Main harmonic source in power supply system of urban rail transit is below:
Traction rectifier inverter device produce high harmonic(11times, 13times etc.)
Others are from large nonlinear load of transformer(3times, 5times, 7times)
Harmonic quantities and kinds are increasing with the updated devices and increasing passenger flow.
Leading harmonic is increasing.
As the traction load is installed in 10KV or 35KV side, normally use the 12 pulse wave rectifier device, harmonic content will be reduced; when harmonic content is within standard, can use for the 0.4KV side control harmonic which produced by second electric group.
Suggest to use passive filter + active filter to conduct harmonic control and reactive compensation:
1)Use fast filter compensation device to improve power factor
2)Use passive filter, can control most harmonic of 5, 7, 11, 13times, to avoid the damage to communication device and electric device from harmonic, reduce active power consumption from harmonic
3)Use active filter, eliminate the interference and electrical active power consumption of important devices from other harmonic
4)Use harmonic voltage suppressor to control 5,7, 11, 13times harmonic voltage