JPH07272822A - Arrester tube - Google Patents

Abstract

PURPOSE:To shut off the continued flow certainly using a small and simple configuration and prevent breakage of an apparatus caused by lightning surge. CONSTITUTION:A pair of main discharge electrodes are provided of which one 12a is made from a shape memory alloy in a cylindrical form, and in the cylinder, a spring 14 which gives a pressing force in the direction of the other main discharge electrode 13a is accommodated. When the first electrode does not get the transform temp., it is elongated and contacts a stopper 15, and a discharge gap is formed between the two main discharge electrodes. When the first electrode attains the transform temp., it is shrunk, and the discharge gap between the electrodes enlarges becomes large.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lightning arrester used in a power supply circuit of a communication device or the like, and more particularly, it is possible to surely interrupt a follow-up current with a small size and a simple structure and to protect a device due to a lightning surge The present invention relates to a lightning arrester that can prevent damage.

[0002]

2. Description of the Related Art Conventionally, a power supply circuit for communication equipment has been
A lightning arrester was provided to limit a large current caused by the intrusion of a lightning surge and to prevent a follow-up current. The lightning arrester according to the conventional example will be described below. First, as a first conventional example, in page 63 of "Lightning Protection Technology Guidebook (NTT Technology Transfer Co., Ltd.), a lightning arrester as shown in Fig. 3 is posted. , A pair of electrodes 102 and 103 are attached to both sides of a cylindrical ceramic envelope (ceramic case) 101, and main discharge electrodes 102a and 103a of these electrodes 102 and 103 are discharged in a cylinder of the ceramic envelope 101. The ceramic envelope 101 has a structure in which an inert gas is filled in the ceramic envelope 101 with a gap left between the main discharge electrodes 102a and 103a when a lightning surge enters a communication device. A high voltage is generated between the main discharge electrodes 102a and 103a, and a dielectric breakdown occurs between the main discharge electrodes 102a and 103a, so that a surge current is discharged to the outside.

Further, FIGS. 4A and 4B are block diagrams showing a surge absorbing circuit for a power source using the lightning arrester of the first conventional example. This surge absorbing circuit for power supply is for limiting a surge current and preventing a follow current.
Here, the follow current means a phenomenon in which a current flows between the main discharge electrodes from a power supply circuit connected to the arrester during or after the discharge because the impedance between the main discharge electrodes becomes low due to the discharge of the surge current. Say.

The surge absorbing circuit for power supply shown in these drawings has a structure in which a resistor 111 or a zinc oxide varistor 112 is connected in series to the lightning arrester 100, and a lightning surge enters a communication device or the like to prevent lightning arrester 21. After discharging the surge current, the resistor 111 or the zinc oxide varistor 112 limits the current flowing from the power supply circuit (not shown) to the surge arrester 100 side to prevent the follow-up current.

A second conventional example is Japanese Patent Laid-Open No. 62-2.
No. 59372 proposes an arrester as shown in FIG. In the figure, an arrester 200 is an insulating tube 201.
Line-side electrodes 202, 202 and ground electrode 20 attached to the
3 is short-circuited by the shape memory alloy short-circuiting plate 204 that is deformed by Joule heat when a follow-up flow occurs. Due to the short circuit of the short-circuiting plate 204, the follow-up current is bypassed to prevent damage to the arrester 200.

As another conventional example, Japanese Patent Laid-Open No. 63-63
No. 47790 includes a main element and an auxiliary element made of zinc oxide, and a shape memory alloy switch part that is reduced and deformed by Joule heat of lightning surge and inserts the auxiliary element. A lightning arrester (zinc oxide varistor) has been proposed in which the main element and the auxiliary element are shared to improve thermal stability.

Further, in JP-A-60-153106,
A lightning arrester (zinc oxide varistor) has been proposed which detects deterioration of a non-linear resistance element made of a metal oxide such as zinc oxide using a coil-shaped shape memory alloy.

[0008]

However, in the arrester according to the first conventional example, the resistor 111 or the zinc oxide varistor 1 is used.
Since a large current flows through 12, the resistor 111 or the zinc oxide varistor 112 must be used for large power, and there is a problem that the shape becomes large. In addition, due to the large current caused by the lightning surge, a high voltage is generated across the resistor 111 or the zinc oxide varistor 112, and the equipment connected to the resistor 111 or the zinc oxide varistor 112 may be damaged.

In the lightning arrester according to the second conventional example, since the line-side electrodes 202, 202 and the ground electrode 203 are short-circuited by the short-circuit plate 204, the current of the power supply circuit is discharged to the outside through the short-circuit plate 204. There was a problem that it would end up. Furthermore, when a surge invades, a large current continues to flow through the short-circuit plate 204, so that the temperature of the short-circuit plate 204 is less likely to fall below the transformation temperature of the shape memory alloy, and the line-side electrode 202,
There is also a problem that the 202 and the ground electrode 203 continue to be short-circuited.

In the lightning arrester of Japanese Patent Laid-Open No. 63-47903,
Since the number of zinc oxide elements increases due to the insertion of the auxiliary element at the time of surge intrusion, the voltage across the lightning arrester becomes high, and a high voltage may be applied to the device connected to the lightning arrester, causing damage. was there. In addition, JP-A-60
The lightning arrester of No. 153106 only detects the deterioration of the non-linear resistance element, and there is a problem that damage to the lightning arrester and the device cannot be avoided unless the lightning arrester is replaced. The surge arresters of JP-A-63-47903 and JP-A-60-153106 have a problem that the surge resistance is small because zinc oxide is used as a main element, an auxiliary element and a non-linear resistance element. .

The present invention has been made in view of the above problems, and a surge arrester capable of reliably interrupting a follow-up current with a small and simple structure and preventing damage to equipment due to a lightning surge. For the purpose of provision.

[0012]

In order to achieve the above object, an arrester of the present invention is mounted on a cylindrical ceramic case and both sides of the ceramic case, and the main discharge electrodes of each are opposed to each other in the cylinder. In a lightning arrester consisting of a pair of electrodes, at least one main discharge electrode of the pair of main discharge electrodes is formed of a cylindrical shape memory alloy, and the other of the main discharge electrodes is formed in the cylinder. A spring for applying a pressing force in the direction of the main discharge electrode is housed, and when the one main discharge electrode does not reach the transformation temperature, the one main discharge electrode is in an extended state and is between the pair of main discharge electrodes. A discharge gap is formed, and when the one main discharge electrode reaches the transformation temperature, the one main discharge electrode is contracted and the discharge gap between the pair of main discharge electrodes becomes large. Configured, preferably before In the ceramic case, the tip of the main discharge electrodes in a state where extended contacts, a structure in which a stopper to form a discharge gap between the pair of main discharge electrodes.

[0013]

According to the lightning arrester of the present invention having the above-mentioned structure, when a follow current is generated after discharge due to intrusion of a lightning surge, the one main discharge electrode reaches the transformation temperature of the shape memory alloy by the follow Joule heat. . Then, the metal structure of the one main discharge electrode changes to an austenite phase and becomes hard, and the spring housed in the cylinder is pushed back and contracted. As a result, the discharge gap between the pair of main discharge electrodes becomes large, and the follow current is interrupted.

[0014]

Embodiments of the lightning arrester of the present invention will be described below with reference to the drawings. FIG. 1 shows a lightning arrester according to the present embodiment. FIG. 1 (a) is a longitudinal sectional view of the lightning arrester when a follow current is not generated, and FIG. 1 (b) is an A- line in FIG. 1 (a).
FIG. In the lightning arrester of the present embodiment, of the pair of opposing main discharge electrodes, one main discharge electrode is made expandable by a shape memory alloy and a spring, and the one extended main discharge electrode is The stopper is provided at a position where a discharge gap is formed between the main discharge electrode and the main discharge electrode.

In these drawings, 11 is a cylindrical ceramic case, and a pair of electrodes 12 and 13 facing each other are attached to both sides of the ceramic case 11. Main discharge electrodes 12a and 13a are formed on the pair of electrodes 12 and 13, respectively, and the main discharge electrodes 12a and 13a face each other in the cylinder of the ceramic case 11.

Of the pair of main discharge electrodes, one main discharge electrode 12a is formed of a cylindrical shape memory alloy, and a spring for applying a pressing force in the direction of the other main discharge electrode 13a is formed in this cylinder. 14 are stored. Further, as the shape memory alloy forming one main discharge electrode 12a, one that reversibly deforms in shape due to temperature change (bidirectional shape memory alloy) is used, and when the transformation temperature is not reached, the metal structure is It has the property of becoming a soft martensite phase, and conversely, when the transformation temperature is reached, the metal structure becomes a hard austenite phase. Here, as the shape memory alloy, one whose transformation temperature is slightly higher than the temperature of the atmosphere in which the present arrester is installed is used. This one main discharge electrode 12a
Flange portions 21a and 21b are provided on both ends of the electrode, respectively, and are fixed by screwing the flange portion 21a at the lower end into the mounting portion 30 formed in the one electrode 12. Note that the one main discharge electrode 12a is not limited to screwing, and may be directly soldered and fixed to the one electrode 12.

Another main discharge electrode 1 of the ceramic case 11.
A stopper 15 is integrally formed on the inner wall surface near the position corresponding to the tip of 3a so as to contact the flange portion 21b at the upper end when one main discharge electrode 12a is in an extended state. In addition, an inert gas (not shown) is sealed inside the ceramic case 11.

Next, the operation of the lightning arrester of the present embodiment having the above structure will be described with reference to FIGS. 1 (a) and 2. FIG. 2 is a vertical cross-sectional view showing the present lightning arrester when a follow flow occurs. One main discharge electrode 12 when no follow current is generated
In a, the transformation temperature of the shape memory alloy is not reached, and the metal structure is a soft martensite phase. As a result, the one main discharge electrode 12a is pressed by the spring 14 toward the other main discharge electrode 13a and is extended to the position of the stopper 15. At this time, the pair of main discharge electrodes 1
A discharge gap is formed between 2a and 13a.

In such a state, when a lightning surge enters, discharge of a surge current is started between the pair of main discharge electrodes 12a and 13a. Then, the pair of main discharge electrodes 12
Since the impedances of a and 13a are low, a follow current is generated from the power supply circuit (not shown) to the arrester. Due to the Joule heat due to this continuous flow, one main discharge electrode 12a
Reaches the transformation temperature of the shape memory alloy. Then, the metal structure of one main discharge electrode 12a changes to an austenite phase and becomes hard, and the spring 14 is pushed back and contracted (FIG. 2). As a result, the discharge gap between the pair of main discharge electrodes 12a, 13a facing each other becomes large, and the follow current is interrupted. When the follow current is cut off and the temperature of the one main discharge electrode 12a becomes lower than the transformation temperature of the shape memory alloy, the one main discharge electrode 12a returns to the extended state as shown in FIG. Prepare for intrusion.

According to the lightning arrester of this embodiment having such a structure, one main discharge electrode 12a is formed of a shape memory alloy, and the other main discharge electrode 13a is formed by the spring 14.
With a simple configuration in which the surge arrester is pressed in the direction of, the surge arrester can be miniaturized and the follow-up current can be reliably cut off. Further, since the present arrester can interrupt the follow-up current without providing a resistor or a zinc oxide varistor, it is possible to prevent damage to the equipment due to high voltage.

The lightning arrester of the present invention is not limited to the above embodiment. For example, although only the main discharge electrode 12a of the first embodiment is configured to be expandable and contractible by the shape memory alloy and the spring 14, only the other main discharge electrode 13a or both the main discharge electrodes 12a and 13a are shaped memory alloy. A flexible structure may be used by using a spring and a spring. When both of the main discharge electrodes 12a and 13a are configured to be expandable and contractible, the main discharge electrodes 12a and 13a are generated when a follow current is generated.
The discharge gap can be made larger, and the follow current can be blocked more reliably. Further, if one main discharge electrode 12a extends only to a certain length when the transformation temperature is not reached, the same effect as in the above embodiment can be obtained without providing the stopper 15.

[0022]

As described above, according to the lightning arrester of the present invention, the follow-up current can be reliably cut off with a small size and a simple structure, and damage to the equipment due to a lightning surge can be prevented.

[Brief description of drawings]

1A and 1B show a lightning arrester according to an embodiment of the present invention. FIG. 1A is a vertical cross-sectional view of the lightning arrester when a follow current is not generated, and FIG. FIG.

FIG. 2 is a vertical cross-sectional view showing the present lightning arrester when a follow current occurs.

FIG. 3 is a partial cross-sectional perspective view showing a lightning arrester according to a first conventional example.

4A and 4B are block diagrams showing a surge absorbing circuit for a power source using the lightning arrester of the first conventional example.

FIG. 5 is a front view showing a lightning arrester according to a second conventional example.

[Explanation of symbols]

 11 Ceramic Case 12 One Electrode 12a One Main Discharge Electrode 13 Other Electrode 13a Other Main Discharge Electrode 14 Spring 15 Stopper 21a, 21b Flange Part 30 Attachment Part

Claims (3)

[Claims] 1. A lightning arrester comprising a cylindrical ceramic case and a pair of electrodes mounted on both sides of the ceramic case and having main discharge electrodes facing each other in the cylinder. The one main discharge electrode is formed of a cylindrical shape memory alloy, and a spring for applying a pressing force in the direction of the other main discharge electrode is housed in the cylinder of the one main discharge electrode. Does not reach the transformation temperature, the one main discharge electrode is in an extended state to form a discharge gap between the pair of main discharge electrodes, and the one main discharge electrode reaches the transformation temperature. When I did
A lightning arrester characterized in that the one main discharge electrode is contracted to increase a discharge gap between the pair of main discharge electrodes. 2. A spring for forming both of the pair of main discharge electrodes from a cylindrical shape memory alloy and applying a pressing force in the center of the ceramic case in the cylinders of the pair of main discharge electrodes. The lightning arrester according to claim 1, which accommodates the lightning arrester. 3. A stopper provided in the ceramic case, the tip of the extended main discharge electrode being in contact with the ceramic case to form a discharge gap between the pair of main discharge electrodes.
Alternatively, the arrester described in 2.