JPH03250575A - Molybdene lightning arrester - Google Patents

Abstract

PURPOSE:To achieve a lightning arrester in simple structure and provide its manufacturability at a low cost by enabling repeated service through utilization of the fact that dielectric breakdown of a Mo metal film due to discharging is recovered at the same time as ending of the discharge. CONSTITUTION:The surfaces of two electrodes made of Mo are oxidized thermally or chemically to form an oxidation film. As the dielectric withstand voltage differs depending upon the thickness of the film, an adjustment is made so as to attain a thickness corresponding to the required withstand voltage. The electric wave signal is grounded 4 from an antenna 1 via a conductor 2 and a communication apparatus 3. An arrester concerned 12 is grounded 7 through Mo electrodes 5, 6 in connection to the middle point of the conductor 2 leading from the antenna 1 to communication apparatus 3. At normal times the part between these electrodes 5, 6 is kept insulated by the oxidation film, and the electrostatic capacity between the two is very small, so that little electric waves run off to the ground. When a lightning surge 11 proceeds in the direction of arrow, it is discharged to the ground 7 via the electrodes 5, 6 through Mo film having a very low operating voltage.

Description

[Detailed Description of the Invention] This invention allows high frequency currents such as radio signals or other weak voltage currents to pass through easily, but large shock wave currents such as those caused by direct lightning strikes can pass through instantly to restore the insulation, and it is difficult to break. This is a lightning arrester with the following features.

Conventional technology If you try to protect a weak current circuit such as an antenna circuit, 3
Lightning arresters that operate at low voltages below 00V are required.

However, the zinc oxide type lightning arrester has the disadvantage that as the device operates at a low voltage, the capacitance increases, resulting in increased high frequency loss.

For this reason, conventionally, an air discharge gap with low capacitance or a special gas-filled discharge tube has been used.

The disadvantage of these is that the discharge gap 1 of the former must be discharged at an extremely low voltage of 300V, so the gap length between the 4J jumps of both sides is extremely short, less than 1/10 of a millimeter. There was a disadvantage that the electrodes were melted and welded by lightning, resulting in short circuit damage. The latter gas-filled discharge tube had the disadvantage that the gas substance changed and was easily broken by a direct lightning strike.

Problems to be solved by the present invention and means for solving them.

In the present invention, the surfaces of both electrodes made of molybdenum are thermally or chemically oxidized to form an oxide film.

The dielectric breakdown voltage of this molybdenum oxide film varies depending on its thickness, and the thickness corresponding to the required breakdown voltage is determined thermally by temperature, time, and oxygen amount, and chemically by the type, concentration, temperature, and current value of the electrolyte. can be freely created by

By bringing the electrodes obtained in this way into close contact with each other, it is possible to obtain a lightning arrester that is difficult to pass the above-mentioned high frequency current, easy to pass the 1irt current, and difficult to break.

Therefore, the present invention solves the problem of melt MW circuit between both electrodes during discharge, which is common in conventional gear type M lightning devices.

The operation, embodiments, and effects of the present invention will be specifically explained with reference to the drawings.

Now, the radio signal passes from antenna 1 through conductor 2 to communication 11.
It passes through 3 and connects to the earth 4, fulfilling its original purpose as a radio signal.

The lightning arrester 12 of the present invention is connected to the middle of the conductor 2 connecting the antenna 1 and the communication 113, and is connected to the ground 7 through the molybdenum electrode 5 and the molybdenum electrode 6.

Under normal conditions, insulation is maintained between molybdenum electrode 5 and molybdenum electrode 6 by their respective oxide films, and the electrostatic capacitance of both is extremely small, meaning that only a small amount of radio waves are allowed to escape to the ground. It does not interfere with the purpose.

However, when the lightning surge 11 advances in the direction of the arrow, the lightning surge 11 conducts from the electrode 5 to the electrode 6 and discharges out to the ground 7 because of the molybdenum oxide film that has settled to an extremely low operating voltage.

At this time, the breakdown voltage of the communication device at the radio wave input terminal generally has a withstand voltage of about IKV with a 1/40 μs surge voltage waveform, so this lightning arrester, which operates at a lower voltage, will destroy the communication device 3. It is possible to operate earlier than the above to protect the communication device from lightning strikes.

The operational status of this lightning arrester will be observed and discussed through experiments.

FIG. 2 shows a longitudinal section of the molybdenum electrode 5 and the molybdenum electrode 6 in contact with each other, and the oxide films on both electrodes are shown by hatching.

Now, the high frequency voltage received by the antenna passes through the conductor 2 and charges the molybdenum electrode 5.

The high frequency current tries to flow from the molybdenum electrode 5 to the molybdenum electrode 6, but the molybdenum oxide film 8.9.10. It is blocked by such things and cannot flow.

This is because the high frequency voltage does not reach the voltage required to destroy the insulating oxide film.

The dielectric breakdown voltage of the coating can be freely set by changing the thickness of the coating, but let us assume that it has been set to 250 .ANG., and now a surge of about 10 KV is applied to the coating.

In this case, the lightning surge voltage of 10 KV is much higher than the set voltage of the coating, 250 V, so the insulating liquid is 118.9 KV.
．． 10. Concentrate on the parts that are easy to pass through.

8.9.10. are the contact surfaces of the electrodes 5 and 6, and are not particularly divided.The ideal is to have equal and consistent contact surfaces with dielectric strength, but it is not easy to eliminate variations in construction, so there is no way to do so. However, there will be some differences in dielectric strength.

Therefore, if the contact surface is 8.9.10. This is what I try to explain by separating them.

Returning to the main topic, the lightning surge passes through the molybdenum pole 5.6 and escapes to the earth 7.

It is assumed that the lightning surge current flows several thousand amperes or several thousand amperes, but for a time of about 1/100,000 seconds, when passing through the contact portion 8 between the two poles.

At this time, when the contact part 8 of both poles overheats and the thickness of the oxide film increases, the dielectric strength voltage also increases. Therefore, in the next lightning strike, parts with lower dielectric strength voltage than the contact part 8, for example, the contact part 9, will be affected by the lightning surge. It becomes a path that can be followed.

In this way, in the next lightning strike, the contact portion 10 becomes the passing point for the lightning surge, and the MM effect is achieved because the location does not change from the next primary.

According to experiments, surge current waveform 8/20μS, 4000
At A1 second intervals of 2 and < 1000 times, no failure occurred and it was confirmed that it could be put to practical use.

Formation of molybdenum oxide film Heating method: Heat linear molybdenum with a diameter of 2 mm and a length of about 30 mm in air at 680°C for about 3 hours.

At this time, the air inside the electric furnace seems to have become diluted, but the test sample was completed.

Electrolytic method Connect a molybdenum wire with a diameter of 2 mm and a length of about 30 mm to the positive terminal of a DC power source.

The electrolyte is nitric acid (concentration 62% 1occ > water 90cc liquid temperature
Approximately 14° C. Current IA Current application time 3 minutes Carbon was used as a negative electrode.

When a direct current of 2 V was applied to the electrodes 5.6 as shown in FIG. 2 obtained by the heating method and electrolysis method, there was no leakage current in front of both electrodes.

However, with the 250cm insulation resistance tester, a value close to 0 ohms was obtained, confirming that the current flows more easily when the voltage is close to the above-mentioned operating voltage.

Effects of the Invention Communication antennas located near the height of the mast of ships sailing on the ocean protrude above the ocean and are most likely to receive direct lightning strikes, which can lead to communication interruptions and serious situations. is common knowledge.

It is thought that if such a situation does not occur and it is possible to quickly discharge the discharge into the sea even if a ship receives a direct lightning strike, it will save some life.

The molybdenum lightning arrester of the present invention does not cause the welding phenomenon seen in other lightning arresters that use metal discharge gaps, so it can still be used even after countless discharges and can be put to practical use. We are confident that we will be able to achieve even better results in the future if we continue to conduct experiments and improvements with tens of thousands of amperes of discharge.

Furthermore, the molybdenum lightning arrester of the present invention has a simple structure and can be manufactured at relatively low cost.

As for the range of applications, molybdenum oxide liquid can be used even when the circuit voltage to be protected is high! By stacking the electrodes in series, an even higher activation voltage can be obtained, so it is expected that it will be widely applied.

[Brief explanation of drawings]

FIG. 1 is a wiring diagram showing an example of the principle and implementation of the present invention. FIG. 2 is a longitudinal sectional view showing the principle of the present invention. In Figure 1 and Figure 2, 1 is antenna 2, and wire 3 is connected from antenna 1 to communication 113.
Communication device 4.7. Grounding 5 Molybdenum electrode 6 with an oxide film on the outer surface
are molybdenum electrodes 8.9.10. having the same structure as molybdenum electrode 5. are molybdenum electrode 5 and molybdenum electrode 6
The contact point 11, which was temporarily set up to explain the contact structure with the lightning surge, is the lightning surge, and the arrow indicates the direction of the lightning surge 12
represents the entire invention

Claims (1)

[Claims] A molybdenum lightning arrester utilizes the property that the dielectric breakdown of the molybdenum metal coating due to discharge causes the insulation to recover as soon as the discharge ends.