JP2003219547A - Lightning protection method in steel frame building - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lightning protection apparatus that can prevent damages to electrical equipment caused by reverse flow of induced current, when an indirect lightning stroke occurs. <P>SOLUTION: A cable 3 of a computer 2 and the protected equipment side of a lightning arrester 9 are connected via an arrester conductor 10, and the steel beam 7 between supports 5 and the earth side of the lightning arrester 9 are connected with a conductor (ground wire) 8 via a ground box G. The steel beam 7 has a high electrical resistance (small conductor) relative to the steel support 4 or is insulated, and is not grounded directly to the ground 12. That is, even if an indirect lightning stroke strikes a building, current or static electricity is not generated in the steel beam 7. Thus, a surge current accompanying induced lightning stroke is prevented from flowing in reverse, from the steel beam 7 to the computer 2 side through the lightning arrester 9. <P>COPYRIGHT: (C)2003,JPO

Description

Description: BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a lightning arrester that is provided in a building having a steel structure such as a building and performs lightning arresters on electric equipment in the building when it is struck by lightning or the like. About the method. 2. Description of the Related Art Conventionally, a lightning arrester 13 as shown in FIG. 1 is built as a lightning arrester on a roof of a steel structure building. The lightning rod 13 is a lightning rod 14 that receives a lightning strike.
The lightning rod 14 has one end connected thereto and a lightning conductor 15 for passing a lightning current, and a grounding plate 16 connected to the other end of the lightning conductor 15 and buried in the ground. In general, the lightning rod 14 is erected and fixed on a flat rooftop of the building 1 via a metal support plate 17. Lightning arresters (arrestors, varistors) are attached to electrical equipment in the building. Especially in the wiring of lightning arresters, to prevent lightning currents from penetrating electrical equipment such as computers,
The ground side of the lightning arrester is grounded to a reinforcing bar (referred to as a reinforcing bar) of a building column via a conductor. Here, the function of the lightning arrester is to shunt the current that accompanies the overvoltage caused by lightning when it exceeds a certain value. Thus, the overvoltage is suppressed to protect the insulation of the target device, and the overcurrent and the surge current are interrupted to return the target device to the normal state. [0003] The lightning rod 13
Since the support plate 17 and the lightning conductor 15 of the lightning rod 14 are made of metal, they come into contact with the building 1 and are electrically connected to a conductive part such as a reinforcing bar which is a structure of the building 1. .
For this reason, a lightning current flows through the building, causing induced lightning in laid telecommunications wiring, metal pipes, and the like, thereby causing fragile electrical devices such as computers that are electrically connected and installed in the building to break down. There was a problem. That is,
A general reinforced concrete building is considered to be a "Faraday cage" in which the entire building is covered with reinforcing bars and steel frames, and the entire building is in the form of a metal cage, and no voltage is generated inside the building. However, if current flows through the conductors that make up the cage, if the resistance of the conductor is extremely high (the conductors are thin or the connection to each other is incomplete), if an excessive lightning current flows for that resistance, The impedance drop causes a potential difference between the conductors, and the electric field in the cage also increases. Therefore, when an electric device such as a computer is bridged between two points in the cage by a cable or the like, the electric device receives a potential difference and breaks down. That is, for example, in a reinforced concrete building, due to its structure, an excessive current is generated in a support bar by direct lightning or induced lightning. The main reason for this is that the struts penetrate up and down inside the struts on which the communication lines and the like are wired, and the lower ends of the struts are directly grounded to the ground (electromagnetic induction action). Therefore, for example, when an induced lightning strike occurs around a building, a current may flow along the ground or the like to a support bar, and this current may flow back to an electric device such as a computer via a conductor and a lightning arrester. As a result, there is a problem that a precision electric device is destroyed due to an excessive surge current reverse flow. Particularly, in recent years, with the integration of semiconductor circuits, the resistance value of the internal circuit of the electric device has been reduced, and the damage of the electric device due to the backflow phenomenon has been increasing. The present invention has been made in view of the above problems, and an object of the present invention is to provide a lightning arrester method for a steel structure building that can prevent damage to electric equipment due to induced lightning or reverse flow of surge current in the building. According to the present invention, there is provided a lightning arrester for a steel structure building, the method comprising: connecting a ground wire of an earth box, to which electric equipment in the building is connected, substantially to a center of a beam of the building; It is characterized by being connected to a point. Various electric devices (electronic circuits) are installed in a building, and the electric devices include a distribution board, a personal computer,
It includes medical equipment, communication circuits, power supply circuits, and the like. Also,
The places where electrical equipment is installed are offices, clean rooms, classrooms, operating rooms, manufacturing and assembly of precision equipment and chemical products.
Includes a working room. An appropriate number of lightning arresters are connected to the electric equipment as protected equipment, and a molybdenum lightning arrester or the like is used as the lightning arrester. The ground side of the lightning arrestor is connected to the ground at approximately the midpoint of the beam of the building via a conductor or an earth box. In this case, a method in which one lightning arrester is grounded to a plurality of beam bars, or a method in which two or more lightning arresters are grounded to a single beam bar can be adopted. When an induced lightning strike occurs in a building, a surge current reversely flows from the struts to the electric equipment in the conventional structure, but such a reverse current phenomenon does not occur in the present invention. This is because a surge current of a predetermined value or more does not flow through a beam bar having a high electrical resistance (a thin conductor) or an insulated beam bar with respect to a support bar, and therefore, a surge current flows back to an electric device through a lightning arrester. This is because there is no fear. Therefore, even if an induced lightning strike occurs in the building, the surge current does not flow back to the electric device, so that there is no possibility that the electric device will fail due to the surge current. An embodiment of the present invention will be described below with reference to an embodiment shown in the drawings. The lightning arrester according to the present embodiment is intended for countermeasures against induced lightning in a server room in a building, in which a molybdenum arrester is connected to a computer (electrical equipment) in the server room, and the ground side of the arrester is connected to a beam. It is. FIG. 1 is a conceptual diagram illustrating a lightning arrester method according to an embodiment of the present invention, FIG. 2 is a perspective view of a building schematically showing the lightning arrester method according to the present invention, and FIG. FIG. 4 is a plan sectional view of a building schematically showing a lightning arrester method according to another embodiment of the present invention. FIG. 1 shows a server room 1 in a building such as a building. In the server room 1, a computer (server or client) 2 as a device to be protected is installed. The computer 2 is connected to a conversion hub (not shown), and a power supply cable or a communication cable (hereinafter simply referred to as a cable) 3 from the distribution board 11.
Is connected. The power line of the conversion hub is connected to an outlet of a commercial power supply, and this outlet is drawn into a distribution board of an optical fiber cable (not shown). A lightning arrester 9 is connected to the cable 3 of the computer 2 via a lightning conductor 10. Here, as the lightning arrester 9, for example, one having the same structure as the molybdenum lightning arrester described in Japanese Patent Publication No. Hei 7-118361 is used. This lightning arrester 9 is formed by contacting two molybdenum layers having an insulating oxide film formed thereon with each other. Due to the high conductivity and the oxide film forming property of molybdenum and the insulating properties of molybdenum oxide, the lightning arrester 9 has excellent lightning arrester performance and follow-up interruption. Has performance. That is, when the lightning voltage exceeds a predetermined value during a lightning strike, the lightning arrester 9
When this occurs, the contact portion breaks down and the lightning current flows to the beam 7 side, but after passing the current, an oxide film is formed on the contact portion by an oxidation reaction, and the subsequent flow due to the lightning voltage is interrupted at an early stage. It has become. Reference numeral 4 denotes a support bar of the building 1, which extends up and down in each column 5 of the building 1, and a conducting wire (earth wire) 18 is connected from a support plate 17 of a lightning rod 13 installed on the roof of the building 1. . On the floor beams 6 between the struts 5, there are beam reinforcements 7 extending in the horizontal direction.
A conductor (earth wire) 8 is connected to the ground side of the lightning arrester 9 at a substantially middle point of the beam reinforcement 7 via an earth box G. Since the beam 7 has a high electric resistance (the conductor is thin) with respect to the support 4 due to its structure, even if a guided lightning strikes the building 1,
No surge current or static electricity exceeding a predetermined value is generated in the beam 7. In addition, a grounding plate 16 </ b> A is connected from the lightning rod 13 to the underground 12 via a lightning conductor 15. This grounding plate 16A is a so-called class A grounding work (special type 3 grounding work;
(Electrical / light grounding work).
Class grounding (Class 3 grounding; grounding of machinery and equipment), Class C grounding (Class 2 grounding; grounding of transformers connecting high and low piezoelectric paths), Class D grounding ( First-class grounding work; grounding metal parts of iron and steel arresters, lightning arresters, emitters, and high-voltage cable protection devices for machinery and equipment)
Are electrically connected to the respective grounding plates 16B, 16C, and 16D, and are connected to the support bars 4 of the building 1 buried underground to form an equivalent circuit. Further, a rectangular net 1 formed by a copper wire of 60 sq or more is located directly below the building 1.
9 are buried, and each side of the net 19 is connected to the midpoint of each beam 7 of the building 1 with a conductor 20. This results in a "Faraday cage" in which the entire building is in the form of a metal cage and generates no voltage inside the building. Here, the lightning rod 13 is attached to the top of the building 1, but may be attached to the four corners of the building 1 at an arbitrary interval in order to cope with a lightning strike on the side of the building 1. For example, in the case of a high-rise building or the like, it is desirable to install them at intervals of 50 m. In the above configuration, it is assumed that a lightning current (static electricity) is generated in the cable 3 of the computer 2 due to a lightning strike on the periphery of the building 1 or the like. Then, the current generated in the cable 3 is transmitted through the conductor 10, the lightning arrester 9 and the conductor 8 to the beam 7.
Run away. That is, when a current flows, a voltage equal to or higher than a predetermined value is generated in the lightning arrester 9, and the contact portion of the lightning arrester 9 is broken down, and a current flows to the beam 7 side. And after passing the current,
An oxide film is formed on the contact area to block the downstream flow. As a result, the current does not enter the computer 2 from the cable 3 and a malfunction such as malfunction or failure of the computer 2 is prevented. Here, when a lightning strike occurs in the building 1 or in the vicinity thereof, in the conventional lightning arrester, a surge current may flow backward from the support bar 4 to the computer 2 and damage the computer 2 in some cases. However, in the present embodiment, such a problem is reliably prevented from occurring. That is, even if a surge current flows through the support bar 4, the surge current hardly flows through the beam bar 7 as described above. Therefore, there is no possibility that a surge current flows from the beam 7 to the lightning arrester 9. As a result, even if an induced lightning strike occurs around the building, the current does not flow backward to the computer 2 via the conductor 10 of the lightning arrester 9. Therefore, there is no possibility that the computer 2 is damaged or the like due to the reverse flow of the surge current unlike the related art. FIG. 2 to FIG. 4 schematically show the method of the present invention. An earth box G is installed substantially in the center of the room of the building 1, and a conductor (earth wire) 8 is connected from the earth box G to a substantially middle point of each of the four beam bars 7. The earth box G is connected to a ground wire side of various electric devices such as a computer (not shown). Since the beam 7 has a structurally high electrical resistance (the conductor is thin) with respect to the support 4, even if an induced lightning strikes the building 1, a surge current or static electricity exceeding a predetermined value is generated in the beam 7. There is no. The present invention is not limited to the above-described embodiment, but can be applied to various modifications. For example, in the above embodiment, the lightning arrester 9 and the device to be protected (computer 2)
Is singular, but the lightning arrester 9 and the device to be protected may of course be plural. In the embodiment, the computer 2 is described as an example of the electrical device protected by the lightning arrester 9, but the device to be protected is a (conversion) hub, a distribution board,
Other electrical devices or circuits such as optical fiber cables and related devices may be used. That is, the lightning arrester 9 can be connected to the tension member of the optical fiber and the outlet of the commercial power supply, and each lightning arrester 9 can be grounded to the nearby beam 7 to perform lightning arresters. Further, it is preferable to use shielded wires for the lead-in lines (current lines and voltage lines) in the above embodiment. As described above, according to the present invention, the ground wire of the earth box to which the electric equipment in the building is connected is connected to the substantially middle point of the beam of the building, so that the induced lightning caused by lightning strikes There is an excellent effect that it is possible to prevent the occurrence of troubles such as damage to the electric equipment due to the reverse flow of the surge current or the surge current.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a conceptual diagram illustrating a lightning arrester method according to one embodiment of the present invention. FIG. 2 is a perspective view of a building schematically showing a lightning arrester method according to the present invention. FIG. 3 is a plan sectional view of a building schematically showing a lightning arrester method according to the present invention. FIG. 4 is a plan sectional view of a building schematically showing another embodiment of the lightning arrester method according to the present invention. [Description of Signs] 1 server room (building) 2 computer (protected equipment) 3 power supply cable or communication cable 4 support 5 support 6 support 6 floor beam 7 beam 8 lightning conductor (beam-side ground wire) 9 lightning arrester 10 Lightning conductor (protected equipment side) 11 Distribution board 12 Ground 13 Lightning rod 14 Lightning receiving pin 15 Lightning conductor 16A grounding plate 16B grounding plate 16C grounding plate 16D grounding plate 17 Support plate 18 Conducting wire (post-side grounding wire) 19 Rectangular net Body 20 Conductor G Earth box

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Miyoshi Yamada             176-1 Shiomicho, Miyazaki City, Miyazaki Prefecture (72) Inventor Hiroyuki Yuchi             9889 Ko, Tano-cho, Miyazaki-gun, Miyazaki Prefecture (72) Inventor Masahiro Nishimoto             Miyazaki Pref. (72) Inventor Koji Shimoyoshi             8628 Uedajima, Sadohara-cho, Miyazaki-gun, Miyazaki             26 (72) Inventor Mitsuhiro Yokota             Kiyoshi Nagatomo 1-27, Matte, Kiyotake-cho, Miyazaki-gun, Miyazaki             AP201 (72) Inventor Tomoko Kojima             354-2 Shiromoto, Shinbeppu-cho, Miyazaki-shi, Miyazaki F term (reference) 5G363 AA09 BA01 DB09 DB33

Claims (1)

Claims 1. A lightning arrester method for a steel structure building, wherein a ground wire of an earth box to which an electric device in the building is connected is connected to a substantially middle point of a beam of the building.