输变电基础
一、输电基础 | Transmission Fundamentals
二、线路参数 | Line Parameters
三、系统概念 | System Concepts
Transmission Line Planning — Voltage Selection and Route Design
Gu, the hydropower plant in the western region needs to deliver 2,500 MW to the load center 380 km away. The generation voltage is 18 kV. We need to step it up for efficient long-distance transmission. What voltage level do you recommend for the transmission line, and why?
顾工，西部水电站需要向380公里外的负荷中心输送2,500 MW电力。发电 电压18 kV。需要升压来做高效长距离输电。你建议什么输电电压、为什么？
顾工: For 2,500 MW over 380 km, the optimal transmission voltage depends on the SIL — Surge Impedance Loading — which is the natural loading of the line where reactive power generation from line capacitance balances the reactive power consumption from line inductance. For a single circuit at 500 kV, the SIL is about 900 MW. To transmit 2,500 MW, we'd need at least three 500 kV circuits or a double-circuit 765 kV line. However, considering right-of-way constraints and cost optimization, I recommend a double-circuit 500 kV line with bundled conductors — 4×ACSR 720/50 per phase. Each circuit carries 1,250 MW, giving us 2,500 MW total with N-1 redundancy — if one circuit trips, the other still delivers 1,250 MW.
对2,500 MW传递380公里，最优输电电压取决于SIL——波阻抗自然功率—— 即线路电容产生的无功与线路电感消耗的无功平衡的自然负载。单回500 kV 线路SIL约900 MW。要传2,500 MW，至少需要三回500 kV或者一回双回765 kV。但考虑通道走廊限制和造价优化，建议双回500 kV分裂导线——每相4× ACSR 720/50。每回传1,250 MW，总2,500 MW且满足N-1冗余——一回跳闸、另 一回仍送1,250 MW。
线路工程师: I've completed the route survey using LiDAR data from aerial survey. The optimal route is 380 km across mixed terrain — about 60% flat agricultural land, 25% rolling hills, and 15% mountain crossings at two locations. We've identified 842 tower positions. The average span length is 450 meters. At the two mountain crossings, we have spans up to 1,200 meters — these will require special tall towers, approximately 75-85 meters. The right-of- way width is 50 meters for a double-circuit lattice tower design.
用航测LiDAR数据完成了路径测量。最优路径380公里穿越混合地形——约 60%平坦农田、25%丘陵、15%两处跨山。确定了842基塔位。平均档距450米。 两处跨山有档距达1,200米——需要特殊高塔、约75-85米。双回格构式铁塔 的通道走廊宽度50米。
Substation Planning — Main Connection Scheme Selection
顾工，新建500 kV变电站将是水电站的汇集点并与现有500 kV电网互联。 变电站有2回发电进线、4回电网出线、2台500/220 kV自耦变压器供本地。 建议什么主接线方案？
对这么重要等级的变电站——2,500 MW输送容量、六回500 kV线路——建议 一个半断路器方案。这是最可靠的配置：每两个回路间串联三个断路器、回路 接在断路器之间。任何单个断路器故障都不中断任何回路。甚至任何断路器检 修时全部回路都能保持运行。该方案六回线路需要九台500 kV断路器——比双 母线方案贵，但这个功率级别的可靠性值得这个造价。
500 kV场区采用GIS设计——全部断路器、隔离开关、母线和互感器都封装 在SF6气体绝缘模块中。GIS厂房占地约80 m×25 m，对比同等AIS设计250 m× 150 m——空间节省巨大。220 kV侧采用常规AIS户外布置因为它电压较低且有 空间。两台500/220 kV、750 MVA自耦变压器露天安装在GIS厂房和220 kV场 区之间。