Design technology of line surge arrester
To prevent the trip because of the fault line is one of the important topics of current industrial power transmission power transmission, security. Lightning blackouts flashover and lightning wave intrusion substation caused by insulator string flashover accident of transmission line line, in the southern part of China in 60%, especially the 110kV line, plain lightning rate was 0.1~0.5 times /100km years, the mountains up to 1~4 times /100km · [1]. Installing line arrester (MOA) is to prevent lightning accident, one of the effective methods to reduce failure rate of [2].
The success of reported lightning flashover accident prevention in Japan, Russia, America have many applications Zinc Oxide line lightning arrester. Japan more than 30000 phase 77~500kV line lightning arrester input system in use in twentieth Century 90 in the installing line arrester, achieved good results with the [3].
Our research in this field started late, late start this application and silicon rubber composite coat technology in lightning arrester on the inseparable. Up to now, has developed various types of 110~500kV line lightning arrester, a total of 7610 phase in the system running, received good results. Our line surge arrester with series gap and non gap two series. And the different international is currently gapless arrester accounted for more than 50%.
2, line arrester design technology
Gapless line lightning arrester of successful application benefit from silicone rubber composite, it replaces the original porcelain jacket, so that the quality of 220kV arrester from 260kg to 50kg, so as to realize the suspension mounted on the tower. Line surge arrester with series gap by the arrester body and an external series gap. The body and the general surge arrester, external series gap (GAP) is composed of two ring - ring or rod - rod type discharge electrode.
The arrester body using metal flange sealing at both ends, with nonlinear ZnO resistors and epoxy glass fiber cloth cylinder spring compression, the external use of silicone rubber umbrella skirt seaied. In this way, the arrester greatly reduces the moisture problems caused by "leak".
On the flange design, the classic ball head, ball, are respectively connected with the high voltage end, grounding terminal. In 2003 China Tiansheng bridge - Guangzhou line into the 500kV gap arrester design as an example, in addition to uphold the technology base station lightning arrester, also must solve the following 8 key technical problems:
(1) excellent properties of silicone rubber compound coat
The organic silicone rubber insulation material production lightning arrester composite coat must have excellent resistance to weather, UV resistant, erosion etc.. Compared with porcelain, composite silicone rubber jacket resistance to a large advantage in weight, pollution performance, see table 1. Composite coat can be the selection of materials, a lot of variety.
(2) have the durability of adhesive technology
Zinc Oxide arrester is subjected to tension, Xian Zhen, swaying in the wind, snow and other role in years of use. The bonding part, a lower flange and epoxy glass fiber cloth is lightning arrester load transfer area, also is the weak link of sealing technology. The author thinks, high temperature, high strength epoxy pour mixture and the conical structure is one of the most successful design, the practice also proved this point.
(3) the encapsulation technology of interface
Encapsulated silicone rubber composite coat, flange and epoxy glass cloth tube connection is the appearance of the arrester strengthen the sealing solution, but also to prevent another effective measures electrical erosion. At present, many foreign similar products in the process also failed to achieve this entrapment; but must ensure good bonding between silicon rubber and the flange of various kinds of metal material and heat treatment after plating. In addition, can increase the groove shaped structure under a big small on the flange, the reinforced silicone rubber does not come unglued mechanical stress.
(4) the explosion-proof technology
In order to obtain the good explosion-proof performance in mold pressing vulcanization umbrella skirt epoxy glass fiber tube before the trapezoidal strip processing groove, and special wedge block a blocking tight. The trapezoidal exhaust effect in lightning arrester fault, wedge inserts ensure Injection silicone rubber not into epoxy glass fiber cloth tube. The length, number, explosion-proof force of trapezoidal groove is subject to strict calculation and test for. This type of lightning arrester through the short circuit current test of 40kA and 800A in China and russia.
(5) the absorption energy check
There is a gap line by lightning arrester body and an external series gap. Under normal operation conditions the arrester body charge rate is below 10%, which is mainly subjected to lightning overvoltage, so other properties required of it is greatly reduced. Arrester varistors under lightning overvoltage capability is extremely strong, resistance of 50mm diameter is 4/10ms, the 100kA can withstand high current impulse.
(6) calculation of potential distribution and adjustment
Outstanding technical problems of 330kV, 500kV line lightning arrester is potential inhomogeneity. Unlike the porcelain bushing type lightning arrester, which is suspended in the air, to calculate the potential distribution of [5] by using the finite element method, the three dimensional electric field. Because it is not used in the structure and pressure measure capacitance. Lightning arrester height of more than 5m, if no measures are taken, the potential distribution non-uniform coefficient will reach 1.2, the charge rate 98%. This will accelerate the aging of high field strength at the resistor. Therefore, through the SolidWorks 3D design and improve the design of potential distribution, quantity, and by changing the pressure equalizing ring size, location and depth of the drooping measures such as 500kV gapless arrester (5.4m) potential distribution non-uniform coefficient below 10.4%.
(7) the arrester internal negative pressure
In the lightning arrester is integrally molded injection of silicone rubber process, each part of arrester are heated condition (100 ℃). When the mold pressing vulcanization complete (i.e. arrester sealing finish), after cooling inside will form a low pressure. By "baszyn curve" shows, the resistor flashover voltage is reduced, may damage the arrester in the low voltage. This is the technology problems for manufacturers ignored.
(8) factors affecting the stability of the discharge gap
Stability of gap discharge voltage is the lightning protection performance standards, rod - rod of pure air gap and insulator supporting ring band gap discharge characteristics itself has the difference. The former is extremely non-uniform electric field, the latter is slightly non-uniform electric field; the former is slightly low discharge voltage, small dispersibility, the latter not only dispersed, and the pollution performance of insulators significantly, while pollution caused by the leakage current and reaches a certain value, it with the arrester body leakage current to form a "divider", significantly changed the arrester voltage distribution, improve the arrester discharge voltage value, this is the designer must be given enough consideration.