地铁长大隧道内大功率风机起动对变压器容量选择的影响分析

Influence of High-power Fan Start-up on Transformer Capacity Selection in Metro Long Tunnel

部分地铁隧道的长大区间配备了容量较大的风机,为这些风机配电设置的变压器容量应在保证风机能够正常起动的条件下,达到节约投资和运行费用的目的。依据实际案例,从相关规范和手册入手,通过数据反推验算,得到如下结论:当预接负荷功率小于变压器容量的25%且变压器容量与风机功率之间的最小比值为2.5时,风机可正常起动且变压器容量最小,此比值已得到现场实测验证。同时,针对此情况下按手册给定的保护整定计算公式得到的计算结果不能满足风机起动电流峰值要求的问题,提出采取降低灵敏度来提高整定值的方法,以避免起动过程中变压器高压侧过流保护跳闸。

Some metro tunnel long intervals are equipped with large capacity fans.The transformer capacity set for power distribution of these fans should save investment and operation cost under the premises of ensuring normal start-up.On the basis of actual case,starting with relevant specifications and manuals,through data reverse calculation for verification,the following conclusions are obtained:when the pre-connected load power is less than 25%of the transformer capacity and the minimum ratio between the transformer capacity and the fan power is 2.5,the fan can start normally and the transformer capacity is the minimum.This ratio has been verified by field measurement.While in this scenario,the results calculated from the protection setting calculation formula given in the manual cannot meet the requirements of the peak starting current of the fan.It is proposed to reduce sensitivity to increase the setting value so that overcurrent protection tripping at the high voltage side of the transformer is avoided during starting process.