KR101569624B1 - MoOx arreste - Google Patents

Abstract

The present invention relates to an arrestor (arrester), and more particularly, it can be used as a low-voltage arrestor element for a communication device such as an antenna and can be applied as an arrestor element for a next generation power protection transmission device alternative to ZnO. To a molybdenum arrester capable of contributing to the improvement of the stability of a power system due to low voltage operation and improving the protection function of a communication equipment and the like.
The molybdenum arrester proposed in the present invention comprises a plurality of molybdenum oxides connected in series, a ceramic material insulator surrounding the plurality of molybdenum oxides, and a conductive electrode covering the upper and lower ends of the plurality of molybdenum oxides, respectively And the gap between the plurality of molybdenum oxides and the insulator is filled with a soho made of SiO ₂ .

Description

Molybdenum arrester {MoOx arreste}

The present invention relates to an arrestor (arrester), and more particularly, it can be used as a low-voltage arrestor element for a communication device such as an antenna and can be applied as an arrestor element for a next-generation power protection transmission device alternative to ZnO. To a molybdenum arrester capable of contributing to the improvement of the stability of a power system due to low voltage operation and improving the protection function of a communication equipment and the like.

Electricity distribution plays an important role in the information society where the safe supply of electric power is essential, and the use environment of electric power equipment is becoming more strict from the viewpoint of economic efficiency and environmental harmony.

Especially, in the urban area, since the paper of power distribution facilities such as substations is very limited, the construction of substations utilizing underground spaces such as large buildings is currently being reviewed and promoted. Especially, the necessity of miniaturization is increasing.

The role of lightning arresters is of utmost importance in performing the insulation protection function in substation equipment.

Up to now, in the development of arrester, research and development have been made in terms of improvement of performance for miniaturization of substation equipment and improvement of miniaturization of arrester itself by improving protection characteristics.

In recent years, a gas insulated switchgear (GIS) using SF6 gas excellent in insulation has been widely used for miniaturization of a substation, and the miniaturization of the lightning arrester is a particularly important task for such GIS use.

Currently, the lightning protection element is a non-linear resistance type using silicon carbide (SiC) or zinc oxide (ZnO) as a base material and an emission type that extinguishes by high pressure gas generated from the electrode surface by arc discharge heat at both ends of the electrode This is the mainstream.

Further, if a weak power circuit such as a conventional communication circuit is to be protected, a lightning arrester operating at a low voltage of 300 V or less is required. Application of a ZnO-based light-emitting element to a device operating at a low voltage has a disadvantage in that the capacitance is large and high frequency loss is large.

Therefore, conventionally, a discharge tube having a small capacity discharge gap or a special gas injected therein has been used.

As a disadvantage of these, discharge gap type discharge must be performed at a very low voltage of 300 V, so that a gap between both electrodes should be kept at a very short distance of 0.1 mm or less. There is a problem that the transition to short circuit breakdown is being raised.

In the case of a gas injection discharge tube, there is a disadvantage in that the gas composition is easily changed at a direct discharge lamp and is easily damaged. Therefore, there is an increasing interest and necessity for developing a lightning protection device having a small size, easy to miniaturize, strong against direct lightning, semi-permanent, small capacitance, and high response speed.

However, currently, ZnO devices occupy the market in the high-voltage line side, but in the case of low-voltage lines, it is difficult to use ZnO devices and development of suitable devices has not yet been made in Korea.

Korean Patent Application Number: No. 1020080051990, entitled " Molybdenum Arrester with Fast Response Time and Method for Manufacturing the Same ", Applicant:

Accordingly, the present invention aims to develop a low-cost, easy-to-manufacture, high-efficiency MoOx device utilizing nano-oxide structure fabrication technology.

For reference, the metal oxide MoOx device proposed in the present invention is an arrestor of a MoOx / Mo structure in which a surface of a metal molybdenum is electrochemically heated to form a nanostructured fine MoOx film on the surface.

The molybdenum arrester proposed in the present invention

A plurality of molybdenum oxides connected in series,

An insulator of ceramic material surrounding the plurality of molybdenum oxides,

And a conductive electrode covering the upper and lower ends of the plurality of molybdenum oxides,

And the plurality of molybdenum oxides and the gap between the insulators are filled with an alumina material of SiO ₂ .

In the case of the present invention, it can be used as a low-voltage arrestor element for communication devices such as an antenna and can be applied as an arrestor element for a next-generation power protection transmission device substituting for ZnO, and contributes to enhancement of stability of a power system due to the semi-permanent characteristics of the device , It is possible to improve the protection function of the communication equipment by the operation of the low voltage.

1 is an example of a device of a molybdenum arrester proposed in the present invention.
2 is an SEM photograph of a MoOx thin film grown on a Si substrate.
3 is an XRD photograph of a MoOx thin film.
4 shows the XRD characteristics of the ZnO thin film obtained by sputtering according to the substrate temperature.
5 shows the XRD characteristics according to the gas flow rate of the SiO ₂ thin film obtained by sputtering
Figs. 6 and 7 are SEM observations of the ZnO thin films obtained by the sputtering method, showing the surface and the fractured surface, respectively.
8 shows the result of SEM observation of the ZnO / SiO ₂ / ZnO thin film formed by the sputtering method.
9 shows the DC voltage-current characteristics of the arrestor element fabricated by sputtering
10 is a view for explaining a method of measuring an arrestor element.
11 and 12 show the impulse voltage-current characteristics of the sample A and the sample B, respectively.
Figures 13 and 14 show a surface photograph and an enlarged photograph of the sample A observed by SEM after the brain impulse test, respectively.
Fig. 15 shows the current-voltage waveform obtained by applying the standard impulse voltage (8/20us) of MoOx arrester against dielectric breakdown and surge voltage.

1 is an example of a molybdenum arrester device proposed in the present invention.

1, the molybdenum arrester proposed in the present invention comprises a plurality of molybdenum oxides connected in series, a ceramic material insulator surrounding the plurality of molybdenum oxides, an upper end portion and a lower end portion of the plurality of molybdenum oxides, Respectively. The gap between the plurality of molybdenum oxides and the insulator is filled with a soho made of SiO ₂ .

The arrestor element of the present invention is one example of a MoOx element, which is manufactured by a general heating method. In the MoOx element, four MoOx elements, which are serially connected elements, are sealed with an insulator and an aluminum electrode of a ceramic material It consists of simple structure.

Between the device and the ceramic insulator is filled with SiO2 for blocking the flow.

In the series gap system, since there is a constant relationship between the gap length and the discharge start voltage, it is possible to adjust the discharge start voltage due to the setting of the gap length.

Molybdenum (Mo), which is an electrode material, has a high melting point (2620 ° C), but also has a characteristic of easily carbonizing by heat (600 ° C) when an overcurrent flows.

The oxide film of Mo has a semiconductor property with high insulation. When Mo is used as a surge suppression element, discharging is started with a very small amount of current as compared with other conventional elements, and surge current is quickly passed through noise surge caused by a surge of a brain due to a junction streamer action, Is about 4 ns, and is known to have a response speed as high as about 20 times that of the conventional one.

The capacitance is also about 1.5-10 써, which is suitable for communication equipments.

And, the molybdenum oxide (MoO3) coating has excellent repetitive ability of breakdown / regeneration of insulation, so that the energy generated from the surge voltage can be released momentarily and the flux can be quickly blocked.

More specifically, it is as follows.

In the case of the metal oxide MoOx device, the MoOx film formed on the electrode surface maintains the insulation property and the capacitance between the electrodes is negligibly small, so that the steady voltage is hardly discharged to the ground, the voltage is not disturbed, The voltage is freely adjustable by adjusting the thickness of the oxide film.

For example, if a normal voltage is set to 250V and an abnormal voltage of about 10kV is applied to the MoOx device, the abnormal voltage of 10kV is much higher than the set voltage of 250V of the oxide film, It passes through the part intensively and flows to the earth.

At this time, as the contact portion is overheated, the thickness of the oxide film increases, and when the dielectric strength of the point rises again, the arrester operation is repeatedly performed while changing the position to another point with low dielectric strength. Therefore, it is possible to perform a so-called repetitive semi-permanent arrestor function in which leakage of current due to a normal voltage is blocked and a large shock wave current such as a lightning stroke is instantaneously discharged to the earth and the insulation property is restored again.

[ MoOx Results of physical property analysis]

In the present invention, the surface characteristics of the MoOx thin film, which is a core element of Arrestor, were investigated.

2 is a SEM photograph of a MoOx thin film grown on a Si substrate using a sputtering apparatus.

In the present invention, a MoOx thin film was fabricated under optimized process conditions at a gas pressure of 8 mTorr, a high frequency RF power of 400 W, an argon-oxygen mixing ratio of 5%, a substrate temperature of 300, and a deposition time of 60 minutes.

The thickness of the MoOx layer was 20 ~ 22 urn, and the temperature and reactivity of the substrate greatly affected the structure and growth of the thin film.

In reactive sputtering, the characteristics of MoOx thin films were investigated under various experimental conditions depending on the oxygen partial pressure, but there was no significant change in the physical properties of the thin films.

3 is an XRD photograph of a MoOx thin film.

The crystal growth orientation of the thin film changed from the (100) plane to the (210) plane depending on the substrate temperature.

It can be seen that the crystal growth of the thin film is controlled according to the substrate temperature.

And, if the temperature of the substrate is increased up to 400, the adhesion and the structural characteristics of the thin film can be improved. The optimal substrate temperature in this experiment was 400.

In the present invention, XPS analysis was also performed on the molybdenum oxide film.

Table 1 shows the XPS spectra of Mo3d and O1s.

ingredient Bonding energy Density ratio
surface
Mo (3d) 228.9 / 232.4 21.6 O (1s) 532.6 76.2 C (is) 292.6 2.2
10 nm depth
Mo (3d) 228.3 / 231.5 26.1 O (1s) 534 73.9 C (is) - -

Table 1 shows the spectral characteristics of each component obtained by XPS analysis. The two peaks of the Mo3d photoelectron indicate that the binding energies were 228.9 eV and 232.4 eV, respectively, and the binding energy of the O1s peak was 532.6 eV.

The peak of carbon (C1s) on the surface was about 292.6 eV in binding energy. This is a common characteristic that is common in XPS analysis.

The C1s peak at the bond energy of 292.6 eV was obtained hourly at the surface of the thin film. These peaks appear to be due to the adsorption of carbon onto the surface as the sample is exposed in the atmosphere during the XPS measurement.

The concentration ratio of molybdenum and oxygen was 21.6: 76.2 in the surface layer and 26.1: 73.9 in the 10 nm depth. From the above results, it was found that a good thin film was obtained.

[Conventional ZnO Wow SiO ₂ Results of physical properties analysis for

In order to compare the performances of ZnO and SiO ₂ , ZnO and SiO ₂ thin films grown on a Si substrate were prepared by sputtering. Table 2 summarizes the manufacturing conditions of the thin film.

Target ZnO (99.99%) SiO ₂ (99.99%) Ar-O ₂ Pressure (m Torr) 20
Rate (sccm) Ar 10 to 50 O ₂ 10 T-S Distance (mm) 50 (constant) RF Power (W) 400 Sputtering time (min) 30 Substrate temperature (℃) room temperature ~ 700 Substrate p-Si (100), Quartz glass

4 shows the XRD characteristics of the ZnO thin film obtained by sputtering according to the substrate temperature.

As shown in FIG. 4, it can be seen that a large difference occurs depending on the heating temperature of the substrate.

The thin film obtained at room temperature had a small peak and a gentle characteristic, indicating that it had amorphous characteristics.

On the other hand, it can be seen that as the substrate temperature is higher, the (002) peak grows and a sharp peak appears from 300 and crystallize.

5 shows the XRD characteristics according to the gas flow rate of the SiO ₂ thin film obtained by sputtering.

As shown in FIG. 5, in the case of using only Ar gas, the thickness of the thin film increases and the crystallinity tends to deteriorate as the sputter rate increases.

Therefore, it can be confirmed that the thin film has a small and gentle characteristic and shows an amorphous structure.

In contrast, when a thin film was prepared by introducing a reactive gas (O ₂ ), the higher the oxygen partial pressure, the better the crystallinity. When the partial pressure ratio of Ar and O ₂ was 1: 1, the crystallinity was the best.

Figs. 6 and 7 are SEM observations of the ZnO thin films obtained by the sputtering method, showing the surface and the fractured surface, respectively.

As can be seen from the XRD results of FIG. 4, it can be seen that the crystallinity is increased in the thin film having the substrate temperature of 300 by comparing the room temperature and the substrate temperature of 300.

The increase in crystallinity means that the ability to extinguish by arc discharge is improved in the gap between the internal crystal grains when the surge current flows.

8 shows the result of SEM observation of the ZnO / SiO ₂ / ZnO thin film formed by the sputtering method.

As can be seen from FIG. 8, the thickness of the ZnO thin film was 1.4 μm, and that of the SnO ₂ thin film was 300 nm. According to this method, when a surge current flows, a large current passed through the ZnO layer, which is a semiconductor, passes through the SiO ₂ layer, which is an insulating layer, through the tunnel effect, and exerts its effect on the ground.

Although the SiO ₂ layer has excellent dielectric strength, when the thickness of the thin film is minimized in the nm range as shown in the figure, a large current flows through the insulating layer due to the tunnel effect. In this process, the surge current can be suppressed and the system can be protected. The fabrication conditions of the ZnO / SiO ₂ / ZnO thin film are summarized in Table 3.

Thin film structure Sputtering conditions
ZnO / SiO2 / ZnO
ZnO (1) Target: ZnO compound, 4-inch diameter
Gas: Ar + 02, 20 mTorr, RF power: 400 W, Si substrate temperature: 700 캜 ZnO (2) Target: ZnO compound, 4-inch diameter
Gas: Ar + 02, 20 mTorr, RF power: 400 W, Si substrate temperature: 700 캜

[ ZnO / SiO ₂ / ZnO  Nonlinearity result of method]

9 shows DC voltage-current characteristics of the arrestor element fabricated by sputtering.

It can be seen that nonlinearity is exhibited in the voltage-current characteristics when positive polarity and negative polarity are applied to the upper electrode.

There are various theories about how the arrestor passes the abnormal voltage and current, but from the experimental results, the theory known as the orthodox is the dual sort key barrier model.

In the arrester of ZnO / SiO ₂ / ZnO junction structure, nonlinear characteristics are shown in the bipolar direction, indicating that a double Schottky barrier is formed.

A number of levels are formed in crystal grain boundaries by additives added to ZnO, and a double Schottky barrier is formed to compensate the charge of the electrons collected at these levels. When a voltage is applied to the device, some electrons are excited and cross this barrier.

When the electrons in the valence band receive the energy of the electrons passing through the barrier, holes are formed in the valence band. These holes move and combine with the electrons at the interface level to lower the barrier. This causes the current to flow rapidly.

On the other hand, from the experimental results of FIG. 9 showing asymmetry according to the polarity direction, it can be seen that the reason for the asymmetry is due to the difference in donor density between the first ZnO thin film and the second ZnO thin film.

[ MoOx Aristarch  Thin film device Impulse  Performance Test Results]

In the present invention, current-voltage characteristics and lifetime evaluation were performed by applying a standard impulse voltage of 8/20 占 퐉 several times to the MoOx thin film type arrester manufactured by the sputtering method.

The standard impulse voltage was generated using a surge tester, and waveforms were observed with an oscilloscope and a computer.

FIG. 10 is a view for explaining a method of measuring an arrestor element, and the manufacturing conditions of the MoO.sub.x arrestor used in the evaluation are shown in Table 4.

Sample A Sample B  target MoOx MoOx Ar-O ₂ pressure (mTorr) 20 20 Gas flow rate (Ar: O ₂ ) 40: 4 40: 4  Target-substrate distance (mm) 100 100  RF power (W) 400 400  Substrate temperature (캜) 600 600  Substrate Material Mo Mo  Sputter time (min) 120 60  Heating temperature (℃) R. T. 600  Heating time (min) 0 30  Masking O X

11 and 12 show the impulse voltage-current characteristics of the sample A and the sample B, respectively.

Figures 13 and 14 show a surface photograph and an enlarged photograph of the sample A observed by SEM after the brain impulse test, respectively.

8/20 탆 standard impulse As a result of measuring the resistance between devices before the high current test, it was confirmed that Sample A and Sample B were in an insulated state.

Sample A was operated at an applied voltage of 900 V, and the insulation properties were measured immediately after the test. As a result, it was confirmed that the insulation properties remained unchanged.

Thereafter, the test was conducted 20 times at an applied voltage of 900 V, and the insulation properties of the device after the test were examined. As a result, it was confirmed that the insulation property was maintained without any significant change.

Similarly, in the case of Sample B, a current started to flow at an applied voltage of 700 V, and after 20 times impulse test, it was confirmed that the insulation property was maintained as it was.

In principle, when the impulse voltage is applied, a gap discharge occurs in the micro gap between the MoOx particles, and the large current is determined to be extinguished.

As a result of the test, the produced arrestor element maintains its insulation property.

Fig. 15 shows the current-voltage waveform obtained by applying the standard impulse voltage (8/20us) of the MoOx arrester to insulation breakdown and surge voltage conducted by the Institute of Basic Electricity, May 2013.

It was found that the light emission signal from the photomultiplier tube occurred in the MoOx element sample due to the surge voltage generated during the insulation breakdown.

Discharge tests with surge voltage were performed 10 times continuously.

From the current-voltage characteristic curve, initial and average resistance values of the samples were 1.4 and 800 kOV, respectively, when a voltage of 400 V was applied.

Next, Table 5 shows the results of a comparative experiment in which a molybdenum oxide thin-film transmission element sample (A) without heat treatment and a heat-treated molybdenum oxide thin-film transmission element sample (B) were produced.

Experimental conditions Sample A Sample B

Ar / O ₂ (10%)


Substrate temperature A constant temperature 400 ° C pressure 18 mTorr 18 mTorr RF power 600 W 600 W Deposition distance 60 minutes 60 minutes Substrate distance 100 mm 100 mm MN field 5 ° / min 5 ° / min

The insulation state of the two samples was confirmed before the experiment, and the repeated operation was superior to the sample (A).

This is considered to be because a plurality of discharge paths are formed between the gaps of the heat-treated MoOx devices.

As can be seen from the above, it can be seen that the MoOx thin film prepared in this study is very useful from the viewpoint of the application of the arrestor.

Consequently, in the present invention, a MoOx thin film was formed by sputtering for application to arrestor.

MoOx thin films were investigated through XPS and SEM analyzes. As a result, good uniformity of MoOx thin film was obtained by sputtering device of ± 0.26%.

The emission, voltage, current, and resistance values of the MoOx thin film were measured while adjusting the gap length of the MoOx thin film with a standard impulse voltage (8 / 20us) applied. As a result, The average insulation resistance values were 1.4 MO and 800 K OMEGA, respectively.

As a result of the deposition of the MoOx thin film, it was confirmed that the sputtering method is a very useful system for forming a uniform reactive thin film.

As described above, in the present invention, attention has been paid to molybdenum (Mo) material, which has recently attracted attention as a substitute material of ZnO, and a thin film type next generation lightning prevention device manufacturing method which can meet the above requirements and is further downsized has been proposed.

We also fabricated thin film gap type MoO3 devices by reactive RF sputtering, and investigated the physical properties of the MoO3 element and the characteristics of the annealing process in the thin film fabrication process.

The electrical properties of the Mo element are analyzed and evaluated by current - voltage measurement, surface analysis and comparison with ZnO.

Claims (1)

A plurality of molybdenum oxides connected in series,
An insulator of ceramic material surrounding the plurality of molybdenum oxides,
And a conductive electrode covering the upper and lower ends of the plurality of molybdenum oxides,
The molybdenum oxide is formed by sputtering and is formed by heat treatment at a predetermined temperature,
Wherein a plurality of molybdenum oxides and a gap between the insulators are filled with an alumina material of SiO ₂ .

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