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Working principle and structure of zinc oxide lightning arrester

2020-07-17 发布者:Zhejiang Jiuguang Electric Power Technology Co., Ltd.

Compared with ceramic coated zinc oxide surge arresters, composite coated zinc oxide surge arresters have a series of advantages such as small size, light weight, good explosion-proof and sealing performance, large creepage distance, pollution resistance, simple manufacturing process, and compact structure. Therefore, they are popular among users. However, there are also shortcomings such as aging of the coating material and electrical corrosion. At present, in this field, in addition to studying how to improve the characteristics of zinc oxide nonlinear resistors, research is also being conducted on the aging resistance and electrical corrosion resistance of outer insulation materials, as well as improving the internal insulation structure and material properties to compensate for the shortcomings of organic composite materials.
1、 Principle
Zinc oxide ZnO lightning arrester is a new type of lightning arrester developed in the 1970s, mainly composed of zinc oxide varistors. Each varistor has a certain switching voltage (called a varistor) from the time it is made. At normal operating voltage (i.e. less than the varistor voltage), the varistor value is very large, equivalent to an insulating state. However, under the action of impulse voltage (greater than the varistor voltage), the varistor is broken down at a low value, equivalent to a short circuit state. However, the state of the varistor being struck can be restored; When the voltage higher than the varistor voltage is withdrawn, it returns to a high resistance state. Therefore, when installing zinc oxide lightning arresters on power lines, the high voltage of the lightning wave causes the varistor to break down during lightning strikes, and the lightning current flows into the ground through the varistor, keeping the voltage on the power line within a safe range and protecting the safety of electrical equipment.
Structure of Composite Coat Zinc Oxide Surge Arrester
2、 The composite jacket zinc oxide lightning arrester generally consists of the following main components:
a. A series connected zinc oxide nonlinear resistor (or valve) is used to form the valve core;
b. Internal insulation and mechanical strength materials composed of glass fiber reinforced thermosetting resin (FRP);
c. Hot vulcanized silicone rubber outer umbrella cover material;
d. Organic silicone sealant and adhesive;
e. Internal electrodes, external wiring terminals, and fittings.
However, various manufacturers choose different production processes and product structures based on different production and technical conditions. The author selected four representative structures in China for comparative experimental research based on the difference between the resistance plate of the composite outer zinc oxide lightning arrester and the internal insulation structure of the outer insulation umbrella sleeve, in order to obtain the differences in electrical and physical mechanical properties of composite outer zinc oxide lightning arresters with different structures and processes. These four typical lightning arrester structures are shown in Figure
Here, A type, B type, C type, and D type are respectively used to represent epoxy glass fiber prefabricated pipes, resin glass fiber composite winding, resin glass fiber composite winding with resin sealing, and heat shrink plastic sleeves with resin sealing. In addition to these four types, there are also SMC hot pressing, high-temperature curing epoxy resin casting, etc., which will not be studied here for the time being. The outer umbrella cover of the lightning arrester with the above four structures can be prefabricated, so that after high-temperature two-stage vulcanization, the outer umbrella cover material can achieve the optimal electrical and physical properties. The prefabricated umbrella cover is finally bonded and sealed with the core body. In addition, the A and B types of the four structures mentioned above can be directly molded or injected into the insulation of the core to form the outer umbrella cover, but there are certain limitations on the vulcanization temperature and time, otherwise it is easy to cause changes in the characteristics of the internal insulation material and resistor sheet.
In order to improve comparability, all four structures of the test samples were first made into resistor core bodies (rods), then tightly bonded with prefabricated silicone rubber jackets through adhesives, and finally encapsulated at both ends with shielding end caps to form lightning arrester test samples and proportional units. Among them, Type A core bodies encapsulate resistor sheets, electrodes, and springs in epoxy glass fiber tubes; The B-type core is made by winding and heating a non alkali glass ribbon impregnated with epoxy for the resistor and electrode; The C-type core is also made by first winding the resistor and electrode with alkali free glass ribbon impregnated with epoxy, heating and curing them, and then pouring epoxy resin and heating and curing them; The D-type core is first fixed with a heat shrinkable plastic sleeve for the resistor and electrode, and then poured with epoxy resin and heated to cure. The size of the resistor is 34 × 20.5mm.
In addition, in order to study the internal and external insulation performance of lightning arresters, insulation rods were used instead of resistance plates to make insulation specimens that are "shaped like" lightning arresters.
3、 Performance Test and Analysis of Composite Coat Zinc Oxide Surge Arrester
What are the differences in the physical and electrical properties of the four types of composite coated zinc oxide lightning arresters mentioned above? How big is the difference? This is the problem that the author wants to study and solve.
Referring to the relevant standards for composite coated zinc oxide lightning arresters, it can be found that among all the test items, only the following items are related to the internal structure of the lightning arrester, while the rest of the items are unrelated or have little relationship with the lightning arrester structure. Therefore, only the following experimental items will be selected for testing here.


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