JPH0974667A - Composite low-voltage lighting arrester having long life - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a composite low-voltage lightning arrester which can prevent the breakdown of equipment to be protected and the arrester itself even when lightning strikes a point at close range, has a long service life, and does not require maintenance and, at the same time, to stabilize the discharge voltage of the arrester. SOLUTION: A composite low-voltage lighting arrester is constituted by integrally connecting a serial circuit of a lightning arresting element A made of zinc oxide and such a resistor as a metallic resistor inserted into a heat- resistant insulating tube or a ribbon-shaped resistor coated with heat-resistant insulating paint having a large distribution capacitance and a large temperature coefficient in parallel with a spark gap having a large discharge withstand current rating.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lightning arrester for a low voltage which has a high sensitivity, a large energy resistance and a long life. In recent years,
Automation is widespread in a wide range of factories, laboratories, prisons, hospitals, golf courses and other sports facilities, and agricultural facilities, and accompanying electronics devices are widely used. Although these devices are truly weak against lightning surge voltage, it is known that a lightning arrester using a zinc oxide element is effective for protection measures. However, there are various waveforms of the lightning surge that enters. As an example, there is a pulsed abnormal voltage having a short duration, which has little energy even if the voltage is large, and one which has a long current duration and has large energy even if the voltage is low. In the case of a lightning strike, the surge arrester may be thermally destroyed and the protected equipment may be damaged due to the high voltage and long duration. On the other hand, there is a strong demand for lightning arrestors that are compactly assembled, small and lightweight. The present invention is a compact and lightweight arrester that can be assembled compactly, and not only the abnormal high-voltage pulse having a short duration, but the abnormal arrester itself is not destroyed even for an abnormal high voltage having a long duration,
Since the protected device can be repeatedly protected and can be used with almost no maintenance, it is widely used in the field of advanced automation as described above for protecting weak electric devices.

[0002]

2. Description of the Related Art Conventionally, there are a zinc oxide element in which a temperature fuse is connected in series and a composite low-voltage lightning arrester (the basic principle is shown in FIG. 1). The principle of the composite type low voltage lightning arrester is that when an inductive resistor (R ₀ ) is connected in series to a zinc oxide element (A) and a spark gap (G) is connected in parallel, an abnormal high voltage current enters. In addition, an abnormal current is generated in the spark gap (G) without degrading the performance of the zinc oxide lightning arrester (A).
It is known that the equipment to be protected is protected by diversion.

[0003]

The target of the above-mentioned compound type low voltage lightning arrester is that the operating voltage of the lightning arrester is within a stable limit voltage, and at the same time it prevents the protected equipment from being destroyed. Although the composite low-voltage arrester itself is not damaged, the present invention is to further prolong the life of the arrester, and as a result, obtain an ideal maintenance-free arrester.

[0004]

In view of the above situation, in order to solve this problem, a circuit in which a zinc oxide lightning arrester and a resistor having a large distributed capacitance and a large temperature coefficient are connected in series, and a spark is further provided. The gaps are connected in parallel and integrated, and the means will be described from the structure of FIG. 1. First, the spark gap (G) is worn and the zinc oxide lightning arrester element (A) is deteriorated. However, regarding prevention of deterioration of the zinc oxide lightning arrester, Japanese Patent Application No. 1-12 filed by the applicant of the present application
As described in No. 991, the relation of each lightning arrester element shown in FIG. 1 is an equation, and the condition of _RA ≧ (V _S −V) / I ₀ is satisfied. For example, when a lightning surge arrives, the zinc oxide lightning arrester (A) operates only for a slight time delay until the spark gap (G) operates. Since it is commutated to, and only needs to operate very little, it is unlikely that the performance will deteriorate. Moreover, it has been empirically confirmed that the performance of the zinc oxide element itself hardly deteriorates if the waveform is a pulse-like waveform with a short duration. However, in the above equation, R _A is the resistance value of the non-inductive resistor (R ₀ ), V _S is the discharge starting voltage of the spark discharge gap, and V is the zinc oxide lightning arrester (A).
Is the operating voltage, and I ₀ is the surge withstand capability of the zinc oxide lightning arrester (A).

Therefore, the present invention is mainly proposed to prevent the wear of the spark gap (G) of the composite low-voltage lightning arrester. First, in order to prolong the life of the spark gap (G), it is necessary to properly select the material of the spark gap electrode, and to prevent the spark gap (G) from operating unnecessarily and wear it. It is necessary to prevent the cause of The present inventor has empirically learned that, as an electrode material for the spark gap (G), a brass material having a good follow current interrupting property is used for a low-voltage power supply circuit, and a discharge starting voltage is changed for a weak current circuit rather than a follow current interrupting property. However, since there is almost no problem in terms of the material of the electrode material, a zinc oxide lightning arrester (A) and a non-inductive resistor (R) connected in parallel to the spark gap of FIG. 1 are used. ₀ ) of the series circuit is to improve the impedance characteristic of the non-inductive resistor (R ₀ ) to prevent the spark gap (G) from unnecessarily operating.

Therefore, the following three methods are considered as means for improving the impedance characteristics of the non-inductive resistor (R ₀ ). (1) The first method, as shown in FIG. 2, is to connect a zinc oxide element in series to a parallel circuit of a non-inductive resistor (R ₀ ) and a capacitor (C), and The parallel spark gap is less likely to damage the protected device. When a pulsed abnormal voltage with an extremely short duration strikes, the current is mainly the capacitor (C).
Since the voltage drop due to (R ₀ ) is reduced, the abnormal voltage value that invades the protected device is effectively reduced, and at the same time, the voltage applied to the spark gap (G) is also reduced. Therefore, in this case, the spark gap (G) can be prevented from performing an unnecessary operation, and the above object can be achieved.

However, it is very difficult to install a highly reliable capacitor (C) on the actual device which must be designed compactly. It is strongly desired to achieve the same effect as when a condenser (C) is installed. (2) The second method is to select and use an alloy having a relatively large temperature coefficient for the resistor (this resistor is referred to as (R ′)), so that the duration is extremely short and the pulse-like abnormal high voltage is used. When (abnormal high voltage that does not damage the protected equipment) arrives, the temperature of the resistor (R ') is room temperature, so the resistance value is relatively small. Therefore, the potential drop across the resistor (R ') is relatively small and the spark gap (G) does not operate unnecessarily. Further, in a continuous abnormal high voltage current resulting from multiple lightning strokes, long wave tail lightning strokes, etc., the potential drop of the resistor (R ') increases and the spark gap (G) operates. In this way, the spark gap operates efficiently and its life can be significantly increased. (3) The third method combines the measures of (1) and (2) above.

[0008]

As described above, by devising the form of the resistor (R), the distributed capacitance (C ₀ ) of the resistor itself as shown in FIG.
However, when the same effect as when the capacitor (C) is provided is obtained, or when an alloy having a relatively large temperature coefficient of resistance value is selected and used as the resistor (R),
If a pulsed abnormal voltage with an extremely short duration that does not cause damage to the protected equipment strikes, the current will mainly pass through the capacitor (C ₀ ), or the resistor (R ′) will be at room temperature. Therefore, because the resistance value is small or one of the reasons, the potential drop due to the resistor (R ') is reduced and the voltage applied to the spark gap (G) is also reduced. It is possible to prevent unnecessary operation. In the case of an abnormal current with a long duration due to multiple lightning strokes, long wave tail long lightning strokes, etc., the temperature of the resistor (R ') rises, so its resistance value increases and the spark gap (G)
Becomes easier to discharge.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A first example of a resistance element invented for that purpose is shown in FIG. That is, a resistance (R ') formed by bending a resistance wire (for example, an iron nichrome wire) 1 having a large temperature coefficient, which is enclosed in a tube 3 made of a material having excellent heat resistance and withstand voltage (for example, Teflon). And an element integrated with distributed capacitance (C ₀ ) is used (hereinafter referred to as RC element). If structurally necessary, this RC element (B) can be further wound into a coil as shown in FIG. Thus, as shown in FIG. 4, the distributed capacitance (C ₀ ) between the resistors acts as a capacitor, so that the above-mentioned object can be achieved and this structure can be applied to conventional measuring instruments. Since the condition of the “bifiler winding” that has been used has been satisfied, the residual inductance of the RC element (B) can be made negligibly small, which is useful for stabilizing the limit voltage of the arrester. In addition, FIG. 6 shows the zinc oxide lightning arrester (A) and the R of the bifilar winding.
In the figure in which the C element (B) is connected in series by the connection fitting 7,
6 is a terminal. As a precaution, a thermal paper 5 is attached to the zinc oxide lightning protection element (A) so that it can be seen from the outside when the element deteriorates. Normally, the color of the thermal paper 5 is white, but the cause of the deterioration of the zinc oxide element is the temperature rise due to overcurrent, so the color of the thermal paper 5 turns red.

At this time, the shape of the resistor (R ') is shown in FIG.
The ribbon-like shape as described above is advantageous because the distributed capacitance (C ₀ ) of the resistor can be increased. Further, in this case, if the insulating coating 4 is applied to the surface of the ribbon-shaped resistor 2 as shown in FIG. 8 without using an insulating tube, the resistors 2 are more likely to approach each other, so that the distributed capacitance between the resistors is increased. The value of C ₀ can be further increased. In order to make the resistor 2 compact, it is possible to further use it in a spiral shape (FIG. 9) or a chillin shape (FIG. 10).

[0011]

[Effect] The purpose of the composite low-voltage arrester of the present invention is to prevent the equipment to be protected from being destroyed by lightning voltage, and to extend the life of the composite arrester itself to realize a maintenance-free arrester. Is the goal. To do so, it is necessary to obtain a spark gap that does not work unnecessarily.

In order to obtain a spark gap (G) which does not operate unnecessarily, a resistor (R ') having a large temperature coefficient is used,
Utilizing the distributed capacitance (C ₀ ) between the resistors, a series circuit of an RC element and a zinc oxide element (A) having an impedance as if a capacitor (C) is connected in parallel to the resistor (R ′) is formed. By connecting in parallel with the spark gap, a compact compound-type lightning arrester with a spark gap that does not operate unnecessarily can be obtained. Moreover, since the RC element satisfies the condition of "bifiler winding" that has been used for measuring instruments and the like, there is almost no residual impedance of the RC element. An ideal long-life, maintenance-free composite arrester can be easily obtained.

[Brief description of drawings]

FIG. 1 is a basic principle diagram of a compound type lightning arrester.

FIG. 2 is a principle diagram of a compound type lightning arrester having a parallel circuit of a resistor and a capacitor.

FIG. 3 is a diagram showing a distributed capacitance between resistors.

FIG. 4 is a perspective view of an integrated RC element of a resistor and a capacitor.

FIG. 5: Bifilar winding type RC as above
FIG.

FIG. 6 is a perspective view of a lightning arrester in which an RC element and a zinc oxide lightning arrester are integrated as above.

FIG. 7 is a perspective view of a resistance-capacitor integrated RC element using a ribbon-type resistor.

FIG. 8 is a perspective view of the same RC element as above, which is finished by applying an insulating film.

FIG. 9 is a perspective view of the spiral RC element of the above.

FIG. 10 is a perspective view of the above-described chillymen type RC element.

[Explanation of symbols]

A zinc oxide element B RC element R ₀ non-inductive type resistor G spark gap R resistor R'resistor with large temperature coefficient C capacitor C ₀ distributed capacitance 1 metal resistance wire with large temperature coefficient 2 ribbon with large temperature coefficient -Shaped metal resistor 3 Teflon tube 4 Insulation film 5 Thermal paper 6 Crimp terminal 7 Crimp connection fitting

Claims (4)

[Claims] 1. A long-life composite low-voltage circuit in which a zinc oxide lightning arrester, a resistor having a large distributed capacitance and a large temperature coefficient are connected in series, and a spark gap is further connected in parallel to form a circuit. Lightning arrester. 2. The resistor having a large distributed capacitance according to claim 1, is a metal resistor inserted in a heat resistant insulating tube, or a ribbon resistor coated with a heat resistant insulating paint. Then, they were folded back at about the middle and were closely attached to each other. 3. The resistor according to claim 2 can be further formed in a coil state, a spiral shape, or a chilimen shape. 4. The resistor according to claim 1, 2 or 3 is an alloy having a large temperature coefficient such as iron, chrome or nickel.