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1、电力系统的防雷保护包括线路、变电所、发电厂等各个环节。 This topic involves cables, substations, power plants and so on.,8.3 电力系统防雷保护 8.3 Lighting protection in power system,8.3.1 输电线路的防雷保护 8.3.1 Transmission line lightning protection 8.3.2 发电厂和变电所的防雷保护 8.3.2 Lightning protection of power plants and substations,本节内容 Contents i
2、n this section,8.3.1 输电线路的防雷保护 8.3.1 Transmission line lightning protection,在整个电力系统的防雷中，输电线路的防雷问题最为突出。这是因为输电线路绵延数千里、地处旷野、又往往是周边地面上最为高耸的物体，因此极易遭受雷击。 The lighting protection on transmission lines is the most prominent in the entire power system. This is because the transmission lines stretch for thous
3、ands of miles which is located in the wilderness. It is also objects of the large height around. so it is vulnerable to be struck by lightning.,输电线路防雷性能的优劣，工程中主要用耐雷水平和雷击跳闸率两个指标来衡量。所谓耐雷水平，是指雷击线路绝缘不发生闪络的最大雷电流幅值（单位为kA）。 Two indicators such as mine-resistant standards and lightning trip-out rate are use
4、d to estimate transmission line lightning performance of the project. The lighting resistant level refers to the maximum lightning current amplitude when the lightning-line insulation flashover does not occur which unit is kA.,输电线路上的感应雷过电压 Induced lightning over-voltage in transmission lines,雷击线路附近地
5、面时，在线路的导线上会产生感应雷过电压，由于雷击地面时雷击点的自然接地电阻较大，雷电流幅值I一般不超过100kA。 Lightning induced over-voltage will be produced in the line when lightning strikes near the ground . Due to large resistance at the lightning striking point the lightning current amplitude I is generally within 100kA.,实测证明，感应过电压一般不超过300-400kV
6、，对35kV及以下水泥杆线路会引起一定的闪络事故；对110kV及以上的线路，由于绝缘水平较高，所以一般不会引起闪络事故。 It is shown that induced over-voltage is no more than 300-400kV in practice. It will cause flashover incidents to a certain degree for concrete pole lines with voltage 35kV and below. Due to higher levels of insulation in transmission line
7、s of 110kV and above ,the flashover accident can be avoided .,感应雷过电压同时存在于三相导线，故相间不存在电位差，只能引起对地闪络，如果二相或三相同时对地闪络即形成相间闪络事故。 Lightning over-voltage exists in the three-phase wires at the same time , so there is no potential difference. if the two-phases or three-phases flashover at the same time that th
8、e formation of inter-phase flashover accident.,设避雷线和导线悬挂的对地平均高度分别为hg和hc,若避雷线不接地，则根据教材公式(8-18)可求得避雷线和导线上的感应过电压分别为 和 。 Suppose the heights of lightning protection lines and wires are hg, and hc in average. If the lightning protection line is not grounded, induced over-voltage of protection lines and t
9、ransmission lines are and respectively according to formula (8-18) in the textbook.,于是 Therefore,图8-21 有避雷线线路直击雷的 三种情况 Fig.8-21 Three cases of direct lightning stroke on lines,雷击杆塔塔顶；雷击避雷线档距中央；雷电绕过避雷线击于导线，如图8-21所示。 Lightning the top of the tower; Lightning lightning-line span of the Central; Lightni
10、ng strike on the wires to bypass the Ground Wire. They are shown in Fig.8-21,2. 输电线路的耐雷水平 Lightning withstand level of transmission line,而35kV及以下线路一般不装设避雷线，中性点直接接地系统有避雷线的线路遭受直击雷一般有三种情况。 It is not necessary to install the protection lines for 35kV and below . There are three categories in direct ligh
11、tning stroke when neutral point is grounding.,我国110kV及以上线路一般全线都装设避雷线。 Generally lightning protection lines are installed in Chinas for transmission lines of 110kV and above.,（1）雷击杆塔塔顶时的耐雷水平 Lightning resist level when the top of the tower is struck by the lightning,运行经验表明，雷击杆塔的次数与避雷线的根数和经过地区的地形有关，雷击
12、杆塔次数与雷击线路总次数的比值称为击杆率g，DL/T 6201997标准，击杆率g可采用表8-5所列数据。,Operating experience demonstrates that the frequency of lightning on tower and conductors have a relationship with topography of the area and the number of the wires. The ratio of lightning frequency and the total number of lightning on lines is
13、called rod hit rate(g). According to DL / T 620-1997 standard, g can be used in Table 8-5 listed.,表8-5 击杆率 g Tab8-5 g value,雷击塔顶前，雷电通道的负电荷在杆塔及架空地线上产生感应正电荷；当雷击塔顶时，雷通道中的负电荷与杆塔及架空地线上的正感应电荷迅速中和形成雷电流，如图8-22（a）所示 。 Before top of the tower is struck by lightning, positive charge is induced by negative char
14、ge in the thunder channel which is distributed on the towers and transmission lines; when the top of the tower is struck by lightning, the negative charge in the mine channels and the induced positive charge of towers and transmission lines are having a neutralization. There will be a lightning curr
15、ent, which is shown in Figure 8-22 (a).,对于一般高度(40m以下)的杆塔，在工程近似计算中采用图8-22（b）的集中参数等值电路进行分析计算，考虑到雷击点的阻抗较低，故略去雷电通道波阻的影响。 The lumped parameter equivalent circuit shown in Fig.8-22 is adopted to analyze for the tower with average height less than 40m. Impedance in lightning strike channel is usually omitt
16、ed due to the small resistance at the striking point.,图8-22 雷击塔顶时雷电流的分布及等效电路 （a）雷电流的分布 (b) 等效电路 Fig.8-22 The distribution of lightning current and the equivalent circuit when the top of tower is struck(a) The distribution of lightning current (b) The equivalent circuit,（2）雷击避雷线档距中央 The span center of lightning lines is struck,雷击避雷线档距中央时，雷击点会出现较大的过电压，如图8-23所示，根据彼德逊法则，由教材中公式（8-15），雷击点A的电压为： When the span center of lightning conductor is struck, high over-voltage w
