Balance traction transformer is a kind of special transformer for power supply to electric railway, which convert 3 phases to 2 phases and is applicable to direct power supply or BT power supply for electric railway traction system. The traction transformer transmits 100kV power supply to two circuits of 27.5kV single phase traction lines and power the up & down trains respectively. The impedance coefficient of this type of transformer is selectable from a certain range, so it’s easier to meet the impedance matching and guarantee the reliability.
This new type of balance traction transformer has got the national patent, and the patent number is ZL00201821.7.
This transformer has following features:
Simple structure and strong anti short circuit capability: it adopts 3 phases and 3 windings core type, star connection on HV side, lead wire on neutral point, and the secondary side is delta circuit. It adopts constant pressure drying and whole set assembly in manufacturing process, which enhanced the anti short circuit ability.
Low loss: the winding transposition adopts mature “242” style, which can effectively reduced the overall loss and auxiliary loss. Comparing with the power transformer of the same capacity, the off load loss reduced by 10% and on load loss reduced by 20%.
The capacity utilization rate is up to 95.98%, owing to such high utilization rate, the annual operational cost of one unit of 31.5MVA balance transformer could save 10 thousand RMB.
In the condition of non uniqueness fixed of impedance matching, transfer the symmetrical 3-phase power system into 2- phase power system with equal amplitude and 90 degree phase difference. Therefore, when the load of the 2-phase side is equal, the 3-phase side is symmetrical, and when the load of the 2-phase side is unequal, the 3-phase side is balance, which greatly improves and eliminates the influence of negative sequence current in power system.
High overload capacity: it uses reasonable oil circuit structure and winging control technology, so as to make the oil temperature rise and winding temperature rise in relatively low level in case of overload.
BTW could supply 10-63MVA balance traction transformer at 110kV voltage level.