TWI731723B - Power transmission tower with low grounding resistance and grounding device thereof - Google Patents

Abstract

The present invention relates to a power transmission tower with low grounding resistance and a grounding device thereof. The grounding device is electrically connected between tower feet and grounding electrodes and has a metal body and an encapsulation encapsulated the metal body. The resistivity of the encapsulation is lower than the resistivity of soil where the transmission tower is located. By increasing the radius of the encapsulation, the resistance of the encapsulation accounts for more than 90% of the total ground resistance (including earth resistance at infinity). Since the resistance coefficient of the coating layer is lower than earth resistivity, the overall ground resistance is greatly reduced. Furthermore, a construction cost of the grounding device is low and a price–performance ratio of the grounding device is high.

Description

Grounding resistance device of iron tower and iron tower with low grounding resistance device

The present invention relates to a grounding resistance device, especially a grounding resistance device for an iron tower.

Recently, it has been discovered that the phenomenon of reverse flashover of electrical towers has increased. It is believed that due to climate change, the lightning voltage has increased. When the top of the electrical tower is shocked, the lightning current generated cannot be eliminated through the grounding structure of the electrical tower in time, which is a voltage hindrance A voltage drop is formed at the terminal, and this voltage drop exceeds the flashover voltage.

Because the occurrence of reverse flashover will interrupt the power supply, it is necessary to solve and reduce the number of reverse flashovers to ensure smooth power supply.

China Publication No. CN 105514630 A patent for invention discloses a low-impedance absorptive grounding device, which includes a first electrode and a second electrode, which are both buried in the ground; wherein the depth of the second electrode buried in the ground is greater than that of the first electrode buried in the ground. In the underground depth, the potential difference between the lightning current and the distant zero potential point is used to form a capacitance effect, which reduces the impedance of the lightning current release and allows the lightning current to enter the ground smoothly.

However, before the implementation of the grounding device disclosed in the Chinese invention patent, the installation depth of the first electrode and the second electrode must be measured separately and buried in stages. The cost and expense of the implementation are not low, and it is not the best grounding device. .

The Chinese publication CN 109586226 A invention patent discloses a method for suppressing the overvoltage at the tower head of a transmission line during lightning strikes. It connects and installs a coaxial overhead cable, a low-impedance coaxial cable down conductor and a ground lightning arrester in sequence. Finally, connect the ground lightning arrester to the ground network on the iron tower; in this way, when lightning strikes the coaxial overhead cable, the lightning current will pass through the coaxial overhead cable, the coaxial cable down-conductor, the ground lightning arrester and the ground network in sequence, Eventually flow into the ground to reduce the failure of the tower head lightning and insulator discharge flashover.

However, it can be seen from the content of the Chinese patent technology in the previous paragraph that the coaxial overhead cable must be erected on the top of the tower and connected to the ground lightning arrester with a coaxial cable down conductor; therefore, the implementation of this technology requires more equipment costs and The construction cost is not the best grounding device.

In view of the defects of the grounding resistance device of the iron tower disclosed above, the main purpose of the present invention is to provide a new grounding resistance device for the iron tower and an iron tower with a low grounding resistance device.

The main technical means used to achieve the above purpose is to make the grounding resistance device of the iron tower include: a metal body; and a coating layer that covers the metal body and has a resistivity; wherein the resistance of the coating layer The coefficient is lower than the resistivity of the soil layer to be buried.

It can be seen from the above description that the grounding resistance device of the present invention mainly covers the metal body with a coating layer with a resistivity lower than that of the soil where the iron tower is located, so that the coating radius of the coating layer can be increased. , So that the resistance of the cladding layer accounts for more than 90% of the total ground resistance including the resistance at infinity of the earth. In addition, the resistivity of the cladding layer is larger and the resistivity is lower, which can be greatly reduced Overall grounding resistance; therefore, when the tower is struck by lightning, the grounding resistance device of the present invention can reduce the lightning strike energy and avoid the possibility of power outage caused by the reverse flashover damage to the insulation ability of the obstacle, and the overall implementation cost is low and cost-effective.

The main technical means used to achieve the above purpose is to make the tower with low grounding resistance device include: a tower body, which contains four tower feet; multiple grounding electrodes, which are used to insert into the soil where the tower body is located ; And a grounding resistance device, which is electrically connected to the tower feet and the grounding electrodes, and is used to be buried in the soil where the iron tower body is located; wherein the grounding resistance device includes: a metal body, which is electrical Connected to the tower feet and the ground electrodes; and a coating layer that covers the metal body and has a resistivity; wherein the resistivity of the coating layer is lower than the resistance of the soil layer to be buried coefficient.

It can be seen from the above description that the iron tower with a low grounding resistance device of the present invention mainly electrically connects a grounding resistance device between the tower foot and the ground electrode of the tower, and the grounding resistance device is used to coat the metal body. The resistivity of the layer is lower than the resistivity of the soil where the tower is located, so the coating radius of the coating can be increased so that the resistance of the coating accounts for 90% of the total ground resistance (including the resistance at infinity) Above, plus the resistivity of the coating layer is larger and the resistivity is lower, which can greatly reduce the overall grounding resistance (including the resistance at infinity); therefore, the tower of the present invention has the characteristics of low grounding resistance, and when it is struck by lightning , It can reduce the lightning strike energy and avoid the possibility of power outage caused by reverse flashover damage and hinder the insulation ability, and the implementation is low-cost and cost-effective.

1: iron tower

10: Tower body

11: Tower foot

20: Grounding resistance device

20’: Grounding resistance device

21: Metal body

211: Metal Wire

212: Metal Mesh

22: Coating

22’: Medium material

30: Ground electrode

40: soil

Fig. 1A: A perspective view of the first embodiment of the device with low ground resistance according to the present invention.

Fig. 1B: A perspective view of the second embodiment of the device with low ground resistance according to the present invention.

Fig. 2A: A top plan view of the grounding resistance device in Fig. 1A.

Fig. 2B: A top plan view of the grounding resistance device in Fig. 1B.

Fig. 3A: A partial cross-sectional view of the grounding resistance device of the present invention.

Fig. 3B: Another partial cross-sectional view of the grounding resistance device of the present invention.

Figure 4: A graph of the relationship between the radius ratio and the resistance ratio of the grounding resistance device of the present invention.

The present invention proposes a new grounding resistance device for an iron tower. The technical content of the present invention will be described in detail below with a number of embodiments and drawings.

First, please refer to FIG. 1A and FIG. 2A, which is the first embodiment of the low ground resistance device 1 of the present invention, which includes an iron tower body 10, a plurality of ground electrodes 30 and a ground resistance device 20.

The iron tower body 10 is a high-voltage iron tower with four tower feet 11; in this embodiment, the four tower feet 11 are fixed on the ground.

The above-mentioned grounding electrode 30 is in the shape of a rod, which is inserted into the underground soil corresponding to the tower foot 11, and has low resistance and good electrical conductivity.

The grounding resistance device 20 is buried in the soil surrounded by the four tower feet 11, and includes a metal body 21 and a coating layer 22; wherein the coating layer 22 is used to cover the metal body 21 and has a The resistivity is smaller than the resistivity of the soil where the iron tower body 10 is located; in this embodiment, the metal body 21 includes a plurality of metal wires 211, and the first end of each metal wire 211 is electrically conductive Connected to the corresponding tower foot 11, and the other end is electrically connected to the corresponding grounding electrode 30, and the coating layer 22 can be a clay soil, the resistivity of the clay soil is higher than that of gravel with coarse sand The resistivity of the layer or dry and wet loess gravel layer is small.

Please refer to FIG. 1B and FIG. 2B again, which is a second embodiment of the present invention with a low ground resistance device 1. Most of the structure is the same as that of the first embodiment, except that the metal body 21 of the ground resistance device 20' further includes There is a metal mesh 212 which is connected to the metal wires 211 and is also covered by the coating layer 22; in this embodiment, the metal mesh is square, so the second ends of the metal wires 211 They are commonly connected to the four corners of the metal mesh 212, but not limited to this. Therefore, the metal mesh 212 is also buried in the soil surrounded by the four tower feet 11.

As shown in FIG. 3A, the metal wires 211 or the metal mesh 212 of the above-mentioned grounding resistance devices 20, 20' are all covered with a coating layer 22 with a low resistivity and buried in the soil together. Preferably, the metal body is 21 a copper wire, and the low-resistivity coating layer 22 can be a low-resistivity soil, such as clay soil.

Please refer to Figure 3B. For the convenience of construction, trenches 41 corresponding to metal wires 211 and metal meshes 212 can be dug out in advance on the ground of soil 40 covered by the four tower feet 11 of the iron tower, and then a low resistivity coefficient can be laid. After the dielectric material 22', the metal wire 211 and the metal mesh 212 are placed on it, and finally the dielectric material 22' with low resistivity is also covered on the metal wire 211 and the metal mesh 212, so that the metal wire 211 and The metal mesh 212 is covered with a low-resistivity coating layer; preferably, the metal body 21 is a copper wire, and the low-resistivity coating layer may be a low-resistivity dielectric material 22', such as clay soil, etc. .

；其中ρ：包覆層電阻係數；J：電流密度；I：雷擊電流，推導出電壓公式

，其中當包覆層達一定厚度以上(即： r_change/r_conductor~7以上)，即可將包覆層的最外層視為接近於∞，而包覆層的電阻係數即可視為一常數；如此，可再由該電壓公式分別計算出該包覆層的電壓

與該金屬本體的電壓

後；可進一步由包覆層與金屬本體的電壓差值除上雷擊電流[(V_change/V_conductor)/I]，即獲得包覆層與金屬本體的電阻差值：R _change -

；因此，當包覆層半徑夠大(即依據圖4的量測數據：r_change/r_conductor~7以上)時，可簡化該電阻差值為：R _change -R _conductor ~

，由於金屬本體半徑為固定，故此一電阻差值即達到穩定值，完全與圖4所量測數據相符。因此，當本發明的包覆層半徑夠大(夠厚)，其電阻值會佔總接地電阻(含大地無窮遠處電阻)九成以上，再加上包覆層為低電阻係數，故本發明的總接地電阻相較直接將接地極插入土壤的總接地電阻(含大地無窮遠處電阻)大幅降低，而不必再思考如何改善大地無窮遠處電阻，也能大幅降低總接地電阻。 The principle of reducing the total ground resistance of the present invention will be further explained below. The electric field formula E =

; Among them, ρ: coating resistivity; J: current density; I: lightning current, deduced voltage formula

, When the coating layer reaches a certain thickness or more (ie: r _change /r _conductor ~7 or more), the outermost layer of the coating layer can be regarded as close to ∞, and the resistivity of the coating layer can be regarded as a constant ; In this way, the voltage of the cladding layer can be calculated separately from the voltage formula

And the voltage of the metal body

After that, the voltage difference between the coating layer and the metal body can be further divided by the lightning current [(V _change /V _conductor )/I] to obtain the resistance difference between the coating layer and the metal body: R _change-

; Therefore, when the coating radius is large enough (that is, according to the measurement data in Figure 4: r _change /r _conductor ~7 or more), the resistance difference can be simplified as: R _change - R _conductor ~

Since the radius of the metal body is fixed, the resistance difference reaches a stable value, which is completely consistent with the measured data in Figure 4. Therefore, when the radius of the coating layer of the present invention is large enough (thick enough), its resistance value will account for more than 90% of the total ground resistance (including the resistance at infinity of the earth). In addition, the coating layer has a low resistivity. The total grounding resistance of the invention is greatly reduced compared with the total grounding resistance (including the resistance at infinity) of directly inserting the grounding electrode into the soil, without having to think about how to improve the resistance at the infinity of the earth, and can also greatly reduce the total grounding resistance.

The present invention adjusts the radius ratio of the coating layer 22 to the metal body 21 as shown in Figure 2B to be 7, and is actually buried in the soil 40 where the three iron towers numbered #65, #66, and #67 on the Pingtung Changzhi line are located, and The test is carried out, and the test results are shown in the following table 1. The overall grounding resistance of each tower foot 11 (A foot, B foot, C foot, D foot) before and after the installation of the grounding resistance device 20 of the present invention has been significantly reduced for each tower body; Similarly, test them in the soil where the three iron towers numbered # 37, # 38, and # 39 on the Pingtung Neipu line are located. The test results are shown in Table 2 below. Each tower is installed with the grounding resistance device 20 of the present invention. The overall grounding resistance of the front and rear tower feet 11 (A, B, C, D) is also significantly reduced.

Table 1 (Geology A: Pebble and gravel with coarse sandy soil layer)

It can be seen from the above description that the iron tower with a low grounding resistance device of the present invention mainly uses a grounding resistance device which is electrically connected between the tower foot and the ground electrode of the tower, and the grounding resistance device is used to coat metal The resistivity of the body coating layer is lower than the resistivity of the soil where the tower is located. Therefore, the coating radius of the coating layer can be increased so that the resistance of the coating layer accounts for about 90% of the total ground resistance of the tower, which is significantly higher. Reduce the overall grounding resistance of the tower; in this way, when the tower is struck by lightning, the lightning strike energy can be reduced to avoid the possibility of power outage caused by reverse flashover damage to the insulation capacity of the obstacle. Furthermore, since the coating layer of the present invention can directly use low-resistivity soil, only the trench is dug during construction, and the metal body is put in and then buried with the same low-resistivity soil to complete the construction. You only need to prepare Enough metal wires are sufficient, effectively reducing the cost of construction.

The above are only the embodiments of the present invention, and are not intended to limit the present invention in any form. Although the present invention has been disclosed in the above embodiments, it is not intended to limit the present invention. Those with ordinary knowledge in the technical field can make slight changes or modifications to equivalent embodiments with equivalent changes using the technical content disclosed above without departing from the scope of the technical solution of the present invention, provided that they do not depart from the technical solution of the present invention The content, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solutions of the present invention.

1: iron tower

10: Tower body

11: Tower foot

20: Grounding resistance device

30: Ground electrode

40: soil

Claims (6)

A grounding resistance device for an iron tower is electrically connected to a plurality of tower feet of the iron tower and a plurality of grounding electrodes directly and vertically inserted into the soil layer; wherein the grounding resistance device includes: a metal body for horizontally buried Buried in the soil layer; and a clay soil covering the metal body and having a resistivity; wherein the resistivity of the clay soil is lower than the resistivity of the soil layer to be buried. The grounding resistance device according to claim 1, wherein the radius ratio of the clay soil to the metal body is more than 7 times, and the metal system is a plurality of metal wires. The grounding resistance device according to claim 2, wherein the metal system further comprises a metal mesh, and the metal mesh is connected to the metal wires. An iron tower with a low grounding resistance device includes: an iron tower body including four tower feet; a plurality of grounding electrodes for directly and vertically inserting into the soil where the iron tower body is located; and a grounding resistance device for electrical Are connected to the tower feet and the grounding electrodes, and are used to be buried horizontally in the soil where the iron tower body is located; wherein the grounding resistance device includes: a metal body, which is horizontally buried in the soil to be buried, and Are electrically connected to the tower feet and the ground electrodes; and a clay soil that covers the metal body and has a resistivity; wherein the resistivity of the clay soil is lower than the soil to be buried The resistivity of the layer. The iron tower with a low ground resistance device according to claim 4, wherein the radius ratio of the clay soil to the metal body is more than 7 times, and the metal system is a plurality of metal wires, and the metal The first ends of the wires are respectively electrically connected to the corresponding tower feet, and the second ends are respectively electrically connected to the corresponding ground electrodes. The iron tower with a low ground resistance device according to claim 5, wherein the metal system further includes a metal mesh connected to the metal wires.

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