JPH07249502A - Linear resistor - Google Patents

Abstract

PURPOSE:To provide a linear resistor having a high stability and excellent linear current-voltage relations. CONSTITUTION:A linear resistor is composed of a sintered body 1 containing a metal boride by 4-40wt.%, clay by 20-70wt.%, insulating particles by 1.0-70wt.%, and a flux component by 0.1-20wt.% and electrodes 2 and 2' provided on facing surfaces of the sintered body 1 and is used for the closing resistor and neutral grounding resistor of a gas circuit breaker. This linear resistor has stability higher than ZnO-based resistors, carbon-based resistors, and metal boride-glass resistors, and has excellently linear current-voltage relation, and excellent temperature characteristic.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to linear resistors in power equipment, especially circuit breakers and transformers.

[0002]

2. Description of the Related Art As a conventional resistor, a carbon type as disclosed in JP-A-56-4206 and a ZnO type as disclosed in JP-A-63-233502 have been disclosed.

The carbon system has a structure in which carbon powder is dispersed in a matrix made of Al ₂ O ₃ . This resistivity is 10
It is 0 to 1000 Ωcm.

On the other hand, the ZnO-based materials are mainly composed of ZnO.
It is a crystal body containing Al ₂ O ₃ , MgO, Y ₂ O ₃ , Sb ₂ O ₃ , SiO _{2 and the} like. This resistivity is also 100 to 1000 Ωcm and can be used properly depending on the applied device. In this system, the above raw material powders are mixed, an organic binder is added, and the mixture is granulated and molded with a mold. Then, after firing the molded body in an electric furnace,
An electrode is attached to the opposing surfaces to produce a resistor.

[0005] Note that, as the related resistors, for example, Japanese Patent Publication No. 58-21402, Japanese Patent Publication No. 59-51721, and Japanese Patent Publication No.
-147802, Japanese Patent Publication No. 2-3524, and the like. This relates to a thick film composition and has a structure in which electrically conductive LaB ₆ is dispersed in a glass matrix.
Further, a patent that discloses the ZrB ₂ system is disclosed in Japanese Patent Laid-Open No. 232901/1987.
No. These thick film compositions contain an organic vehicle for screen printing with a conductor paste on a substrate such as alumina.

The maximum allowable temperature of this circuit board is 150 ° C.
Then, a large amount of energy is injected like power equipment, and 2
It is not used as a resistor whose temperature rises above 00 ° C.

The present inventors have disclosed in Japanese Patent Laid-Open No. 5-41302 a new resistor having temperature characteristics, current-voltage characteristics and withstand capability. This resistor uses a sintered body made of metal boride and non-reducing glass.

[0008]

A large amount of energy is injected into the power resistor during operation, and the temperature rises to 200 ° C. If the resistance value greatly decreases at this temperature, an excessive current flows and the resistor is destroyed. Since the temperature coefficient of the resistance value of the carbon system is negative, it was necessary to set the allowable temperature to a low value. On the other hand, the ZnO system has a problem that the current-voltage characteristic is poor. Further, the thick film composition is applied to a thick film resistor and is not considered as a resistor having a high energy capacity.

The metal boride-based resistor is a linear resistor whose resistance value hardly decreases up to 200 ° C. and has excellent linearity of current-voltage characteristics. The thermal strength is low and the withstand capability is impaired. In particular, the pulse resistance is poor, and when a high voltage pulse is applied, the conductive path is broken and the resistance value fluctuates.

An object of the present invention is to provide a linear resistor having an excellent withstanding capability without impairing the linearity of the temperature characteristic and the current-voltage characteristic of the metal boride type resistor.

[0011]

In order to achieve the above object, the present invention provides a sintered body containing a metal boride, clay, insulating particles, and a fluxing agent, and a surface of the sintered body facing each other. It is characterized by comprising an electrode. In particular, metal boride is 4 to
40% by weight, 20 to 70% by weight of clay, 1.0 to 70% by weight of insulating particles, and 0.1 to 20% by weight of flux component are desirable.

The firing temperature is suitably in the range of 1000 ° C to 1400 ° C. It does not sinter below 1000 ° C. on the other hand,
Above 1400 ° C, deformation occurs, which is not desirable.

FIG. 1 is a front view of a cylindrical metal boride-based resistor according to the present invention. Reference numeral 1 is a metal boride-based sintered body, and aluminum electrodes 2 and 2'are attached to both surfaces thereof. FIG. 2 shows a front view of a donut type metal boride-based resistor of the present invention. Reference numeral 3 is a metal boride-based sintered body, and 4 and 4 ′ are aluminum electrodes, but a hole 5 is provided at the center of the resistor. Metal borides include LaB ₆ , ZrB ₂ , MoB and Ti.
_{B 2, VB 2, NbB 2} , TaB 2, CrB 2, CaB 6, W 2
One or more kinds of particles selected from B ₅ are desirable. The insulating particles used non-reducing oxides or nitrides, especially alumina. The flux component is preferably at least one selected from non-reducing glass, feldspar, and aluminum silicate.

Further, according to the present invention, a gas circuit breaker and a neutral point grounding resistor are constructed by using this linear resistor.

[0015]

[Function] Metal borides are LaB ₆ , ZrB ₂ , MoB, T
iB ₂ , VB ₂ , NbB ₂ , TaB ₂ , CrB ₂ , CaB ₆ , W ₂
It is a compound such as B ₅ . These particles are essential components in order to have electrical conductivity. In particular, the resistor using LaB ₆ has excellent current-voltage characteristics. A suitable amount of metal boride is 4 to 40% by weight. If it is less than 4.0% by weight, the resistivity becomes more than 5000 Ωcm and it is not suitable for electric power equipment. On the other hand, when it is 40% by weight or more, the resistivity becomes 10 Ωcm or less, which is not suitable for electric power equipment. The resistivity also depends on the particle size of the metal boride. The larger the particle size, the higher the resistivity.

Clay is a plastic powder and is added to facilitate molding and to sinter by heating to a high temperature to increase strength and, consequently, durability. A suitable amount of clay is 20 to 70% by weight. When the amount is 20% by weight or less, the withstand capacity decreases, while the value of 7
If it is 0% by weight or more, the withstand amount is lowered and the sinterability is deteriorated.

In order to improve the thermal characteristics of the resistor and increase the implantation energy, it is desirable to increase the specific heat of the device. Therefore, insulating particles having a large specific heat are added.
The insulating particles having a large specific heat are non-reducing oxides or nitrides having a resistivity of 10 ¹⁰ Ωcm or more. The non-reducing oxide is a component that does not deteriorate even when fired in a reducing atmosphere such as nitrogen, and includes Al ₂ O ₃ , MgO, TiO _{2, and the} like. on the other hand,
The nitride having a large specific heat is Si ₃ N ₄ , AlN or the like. The insulating particles are preferably 1.0 to 70% by weight. If it is less than 1.0% by weight, there is no effect of increasing the durability. On the other hand, 70% by weight
Above, the sinterability becomes poor.

The flux component is non-reducing glass, feldspar, aluminum silicate and other powders. Non-reducing glass is
In addition to SiO ₂ , B ₂ O ₃ , Al ₂ O ₃ , ZrO ₂ , Ca as appropriate
It is a glass that contains O and the like and is not reduced even when heated in a reducing or inert gas such as nitrogen or argon. Feldspar forms glass and densifies the sintered body. If the flux component is less than 0.1% by weight, the sinterability is poor. On the other hand, when the content is 20% by weight or more, the high voltage pulse withstand capability deteriorates.

The bulk type linear resistor is a bulk linear resistor which is distinguished from the thick film type linear resistor by firing after molding.
Metal borides have a structure dispersed in a matrix of clay. The metal boride itself is a conductive particle having a positive temperature coefficient of resistance. A large amount of energy is injected into the power resistor during operation, and the temperature rises to 200 ° C. Due to the connections and insulators in the tank, no more than this temperature is allowed. The temperature coefficient of resistance in the bulk linear resistor of the present invention is -1 x 10 ^-3 to +5 x at a temperature of 200 ° C.
The range of 10 ⁻³ / ° C. is achieved, and the resistance value hardly changes even when the temperature rises.

The current-voltage characteristic is excellent in linearity as compared with the ZnO type.

For the neutral point grounding resistor of a transformer, there is a withstand test in which a current of several to several tens of amperes is passed for several tens of seconds to several minutes to examine the energization time until damage. The linear resistor of the present invention has a much longer energization time than the ZnO type. In this case, the temperature of the resistor rises to 300 ° C or higher. At this time, it is necessary to increase the current and prevent thermal runaway. The function of the linear resistor of the present invention is normally maintained even if the temperature is raised to 300 ° C.

[0022]

EXAMPLES Examples of the present invention will be described below.

[0023] <Example _{1> LaB 6: 120g (12} .
0% by weight), 490 g (49.0% by weight) of elutriated kibushi clay, 350 g (35.0% by weight) of Al ₂ O ₃ and 40 g (4.0% by weight) of Fukushima feldspar were mixed with a lightning striker. La
A powder having a particle size of 1 μm was used as B ₆ . To this, 80 cc of an aqueous polyvinyl alcohol solution was added and granulated. This was molded with a die having a diameter of 50 mm. Put this molded body in an electric furnace,
In a nitrogen atmosphere, the temperature was maintained at 1300 ° C. for 4 hours, and firing was performed. Finally, aluminum was sprayed on both surfaces of this sintered body. This resistor had a diameter of 43 mm and a thickness of 10 mm. The electric resistance of this resistor was 35Ω (430Ωcm).

FIG. 3 shows temperature characteristics. 7 is La of the present invention
A curve of a B ₆ type resistor, a curve 8 of a LaB ₆ -glass type resistor, and a curve 9 of a conventional carbon type resistor. 7 LaB
_{The 6-} system is superior to the 9-carbon system, and has the characteristics at the time of temperature rise as good as the LaB ₆ -glass system of 8. In addition, 10 and 11 are Example 2
And curves of samples 3 and 3.

FIG. 4 is a diagram showing the current density dependence of the resistance value. In this figure, the horizontal axis is the current density and the vertical axis is the electrical resistance. 7'is the LaB ₆ series of the present invention, 8'is the curve of the LaB ₆ -glass series resistor, and 12 is the curve of the conventional ZnO series resistor. The 7'LaB ₆ system and the 8'LaB ₆ -glass system are more linear than the 12 ZnO system. In addition,
10 'and 11' are curves of the samples of Examples 2 and 3.

FIG. 5 shows the AC current resistance. 3 resistors
When an AC current of ~ 4A is applied, it will increase to 30 with the energizing time.
The temperature rises above 0 ° C and finally damages. FIG. 5 shows a change in current depending on the energization time. 7 ″ is the LaB ₆ series of the present invention, 8 ″ is the curve of the LaB ₆ -glass series resistor,
12 'is a curve of a conventional ZnO-based resistor. 7 ″ L
The aB ₆ system has a significantly longer energization time than the 12 'ZnO system, and a 1.5 times longer energization time than the 8 "LaB ₆ -glass system. 10" and 11 "are the same as those in Examples 2 and 3. It is a curve of a sample.

[0027] <Example _{2> LaB 6: 120g (12} .
0% by weight), Tokiguchi Frogme clay 600 g (60.0% by weight), Al ₂ O ₃ 200 g (20.0% by weight) and silicate glass 80 g (8.0% by weight) were mixed with a lightning machine. A resistor was prepared in the same manner as in Example 1. Firing temperature is 11
It was set to 50 ° C. The electric resistance of this resistor is 29Ω (360
Ωcm). The temperature characteristics, the relationship between the current density and the resistance value, and the AC current withstand capability of the samples of the present invention are also shown in FIGS. 3, 4 and 5, respectively. 10, 10 'and 10 "are the curves of the samples of the present invention. These characteristics are conventional carbon based and ZnO.
It is superior to the system.

<Example 3> ZrB ₂ : 180 g (18.0)
% By weight), Tokiguchi Frogme clay 620 g (62.0% by weight), Al ₂ O ₃ 150 g (15.0% by weight) and Al ₂ O
_A resistor was prepared in the same manner as in Example 1 by mixing 50 g (5.0% by weight) of 3.3 SiO ₂ with a lightning striker. The firing temperature was 1350 ° C. The electrical resistance of this resistor is 28Ω
(350 Ωcm).

The temperature characteristics, the relationship between the current density and the resistance value, and the AC current withstand capability of the samples of the present invention are also shown in FIGS. 3, 4 and 5, respectively. 11, 11 'and 11 "are curves of the samples of the present invention. These characteristics are superior to the conventional carbon-based and ZnO-based systems.

Example 4 La having a particle size of 1, 4, 10 μm
B ₆ and LaB ₆ having a particle size of 1 μm, 10% ultrafine LaB ₆
Al ₂ O was added to each of the four LaB ₆ mixed powders
₃ 12.0% by weight, Fukushima feldspar 15.0% by weight, and elutriated kibushi clay were added and mixed by a thunderbolt machine to prepare a resistor in the same manner as in Example 1. The firing temperature was 1100 to 1300 ° C.

FIG. 6 shows the change in resistivity with the amount of LaB ₆ . 14, 15, 16 and 17 have particle sizes of 1 and 1, respectively.
The LaB ₆ in the LaB ₆ and particle size 1μm of 4,10Myuemu 10
5 is a curve of a sample using the mixed powder to which the ultrafine powder LaB ₆ was added. In these curves, the smaller the particle size, the smaller the resistivity. The resistivity of 5000 Ωcm is 4.0 at 17
% By weight, 10.0 by 10% by weight, 15 by 20.0% by weight, and 16 by 27.0% by weight. On the other hand, 1
The resistivity of 0 Ωcm is 7.5% by weight for 17 and 1 for 14
5.0% by weight, 15: 30.0% by weight, 16: 40.
Achieved at 0% by weight. LaB ₆ amount is 4 to 40% by weight
Is an appropriate amount.

Example 5 LaB ₆ , Al having a particle size of 4 μm
₂ O ₃ and Fukushima feldspar were added at different amounts of elutriated wood knot clay and mixed with a thunder pad to prepare a resistor in the same manner as in Example 1. The firing temperature was 1100-1400 ° C.

FIG. 7 shows a change in cumulative injection energy depending on the amount of clay. 18 is a cumulative injection energy obtained from the AC current resistance test. On the other hand, 19 is the cumulative injection energy obtained from the AC discharge withstanding test. The AC discharge withstand test is a test method applied to a resistor for a circuit breaker, with a duration of 10 ms.
Is a test method for investigating the presence or absence of damage to the resistor when discharging 1 to 6 high-voltage AC waves and determining the cumulative injection energy. With respect to the cumulative injection energy obtained from the AC energization resistance test, the resistance decreases when the amount of clay is 25% by weight or less, while the sinterability is deteriorated and the resistance decreases when it is 70% by weight or more. On the other hand, the cumulative injection energy obtained from the AC discharge withstand test decreases when the amount of clay is 20% by weight or less and 50% by weight or more.

<Example 6> LaB _{6 having} a particle size of 4 μm, elutriated kibushi clay and Fukushima feldspar were added at different amounts of Al ₂ O ₃ and mixed with a thunderbolt machine, and the same resistance as in Example 1 was applied. The body was made. The firing temperature was 1100-1400 ° C.

FIG. 8 shows changes in the cumulative implantation energy depending on the amount of Al ₂ O ₃ . 18 'is a cumulative injection energy obtained from the AC withstand voltage test, and 19' is a cumulative injection energy obtained from the AC discharge withstand test. The cumulative implantation energy obtained from the AC energization withstanding test is high in the range of Al ₂ O ₃ 1.0 to 50% by weight. On the other hand, the cumulative implantation energy obtained from the AC discharge withstand test has a high withstand amount in the range of 30 to 70% by weight of Al ₂ O ₃ . When Al ₂ O ₃ is 1.0% by weight or less, there is no effect of increasing the resistance, while when it is 70% by weight or more, the sinterability deteriorates and the resistance decreases.

[0036] <Example 7> LaB ₆ particle size 4 [mu] m, elutriation kibushi clay and Al ₂ O _3, was added by changing the Fukushima feldspar amount, were mixed in a lightning paddle machine, in the same manner as in Example 1 resistance The body was made. The firing temperature was 1000 to 1400 ° C.

FIG. 9 shows changes in the cumulative implantation energy depending on the amount of Fukushima feldspar. 18 'is a cumulative injection energy obtained from the AC withstand voltage test, and 19' is a cumulative injection energy obtained from the AC discharge withstand test. The cumulative injection energy obtained from the AC current resistance test is high in the range of 0.1 to 20% by weight of Fukushima feldspar. On the other hand, the cumulative injection energy obtained from the AC discharge withstand test is high in the range of 0.1 to 10% by weight. Fukushima feldspar has a sinterability of less than 0.1% by weight and does not increase the withstand capacity. On the other hand, when the amount is 20% by weight or more, the withstand amount decreases.

<Embodiment 8> FIG. 10 is an application of the doughnut-type resistor of FIG. 2 for a gas circuit breaker (GCB) closing resistance. This includes a resistivity of 2 produced in the process of Example 1.
A 00 Ωcm resistor is used. The composition LaB ₆ 1
2.6, clay 25, Al ₂ O ₃ 60.4, silicate glass 2.
0 (% by weight) was used. 21 is a resistor element, 22 is an insulating rod, 23 is an insulating cylinder, 24 is a resistor, 25 is a resistance contact, 2
6 is a main contact, 27 is an opening / closing operation piston, 28 is an oil dash pot, 29 is an air tank, and 30 is a bushing. The breaking resistance was 500Ω.

The breaking operation is completed when the main contact 26 opens, a current flows through the resistor 24, and the resistance contact 25 opens.
On the other hand, in the closing operation, the resistance contact 25 is closed and the resistor 24
A current flows through the main contact 26, and the main contact 26 is completed. When the main contact 26 is opened, the resistor 24 carries an AC discharge current of several tens of ms and absorbs an overvoltage.

The specific heat of the resistor element of the present invention used here is 3.0 J / cc · ° C., and the implantation energy per unit volume is 7.
50 J / cc, 2.5 of the conventional metal boride-glass system
J / cc · ℃, exceeded 460 J / cc.

According to the present invention, the resistance is large and the linearity of the resistance value and the temperature characteristic are excellent. Therefore, the number of resistors is smaller than that of the conventional gas circuit breaker using a metal boride-glass system. 50% reduction. Using the numerical values described in the examples, the number of products is reduced by 70% because the withstand capacity is 1.4 times larger.
In order to increase the resistance value by 10% in the high current region, the number is 10
%, And the resistance value at high temperature increases by 20%, so the number can be reduced by 20%. <Embodiment 9> FIG. 11 is an application of the donut type resistor of FIG. 2 to a neutral point grounding resistor of a transformer. This includes
A large resistor having a resistivity of 430 Ωcm manufactured in the process of Example 1 is applied. The composition is LaB ₆ 12.3, clay 5
5.0, Al ₂ O ₃ 20.0, and silicate glass 12.7 (wt%) were used. 21 'is a resistor element, 22' is an insulating rod,
30 'is a bushing, 35 is a tank, and 36 is a grounding point.

According to the present invention, since the resistance of the resistor is excellent, the linearity of the resistance value and the temperature characteristic are excellent, the number of resistors is smaller than that of the conventional gas breaker using the metal boride-glass system. About 50% reduction. Using the numerical values described in the examples, the number can be reduced by 70% because the withstand capacity is 1.5 times larger, and the number can be reduced by 20% because the resistance value at high temperature is increased by 20%.

[0043]

According to the present invention, compared with ZnO-based or carbon-based
Not only the withstand voltage is extremely large, but also the linearity of the current-voltage characteristic and the temperature characteristic are excellent. Therefore, there is an effect that a novel resistor having both the temperature characteristic, the current-voltage characteristic and the withstand voltage can be provided. Furthermore, by applying this resistor, the neutral point grounding resistor and the gas circuit breaker closing resistor can be downsized by 50%,
The number of resistors can be reduced.

[Brief description of drawings]

FIG. 1 is a front view of a cylindrical metal boride-based resistor of the present invention.

FIG. 2 is a front view of a toroidal metal boride-based resistor of the present invention.

FIG. 3 is a temperature characteristic diagram.

FIG. 4 is a current density dependence diagram of resistance values.

FIG. 5 is a diagram showing changes in withstand current of AC energization.

FIG. 6 is a diagram showing a change in resistivity according to the amount of LaB ₆ in the present invention.

FIG. 7 is a diagram showing a change in cumulative injection energy depending on the amount of clay.

FIG. 8 is a diagram showing a change in cumulative implantation energy according to the amount of Al ₂ O ₃ .

FIG. 9 is a change diagram of accumulated implantation energy.

FIG. 10 is a closing resistor for a gas circuit breaker using a donut type metal boride-based resistor.

FIG. 11: S using a donut-shaped metal boride-based resistor
F ₆ gas insulation neutral point grounding.

[Explanation of symbols]

1 ... Metal boride-based sintered body, 2, 2 '... Aluminum electrode, 3 ... Metal boride-based sintered body, 4, 4' ... Aluminum electrode, 5 ... Hole, 7, 7 ', 7 "... Present invention LaB ₆ series resistor curve, 8, 8 ′, 8 ″ ... LaB ₆ -glass series resistor curve, 9 ... Carbon series resistor curve 10, 10 ′,
10 ″ ... Curve of LaB ₆ series resistor of the present invention, 11, 1
1 ', 11 "... Curve of ZrB ₂ system resistor, 12, 12'
... curve of ZnO-based resistor, 14 ... curve of sample with particle size of 1 µm, 15 ... curve of sample with particle size of 4 µm, 16 ... particle size of 10 µm
m sample curve, 17 ... LaB ₆ ultrafine powder sample curve, 18, 18 ', 18 "... AC cumulative injection energy obtained from AC current resistance test, 19, 19', 19" ... AC
Cumulative injection energy calculated from discharge withstand test, 21,2
1 '... Resistor, 22 ... Bushing, 23, 23' ... Insulating rod, 24 ... Capacitor, 25 ... Breaking part, 26 ... Oil dash pot, 27 ... Opening / closing piston, 28 ... Air tank, 29 ... Bushing, 30 ... tank, 31 ... grounding point.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ken Takahashi 7-1, 1-1 Omika-cho, Hitachi-shi, Ibaraki Hitachi Ltd. Hitachi Research Laboratory

Claims (12)

[Claims] 1. A linear resistor comprising a sintered body containing a metal boride, clay, insulating particles and a flux component. 2. A boride of 4 to 40% by weight and 20 to 7
A linear resistor comprising a sintered body containing 0% by weight of clay, 1.0 to 70% by weight of insulating particles, and 0.1 to 20% by weight of a fluxing agent component. 3. A linear resistor comprising a sintered body containing a metal boride, clay, insulating particles and a flux component, and electrodes on opposite surfaces of the sintered body. 4. 4 to 40% by weight of metal boride and 20 to 7
It comprises a sintered body containing 0% by weight of clay, 1.0 to 70% by weight of insulating particles, and 0.1 to 20% by weight of a fluxing agent component, and electrodes on opposite surfaces of the sintered body. A linear resistor characterized by. 5. The metal boride according to claim 1, which is LaB ₆ , ZrB ₂ , MoB, TiB ₂ ,
VB ₂ , NbB ₂ , TaB ₂ , CrB ₂ , CaB ₆ , W ₂ B ₅
A bulk type linear resistor, which is one or more kinds of particles selected from the following. 6. A linear resistor according to claim 1, wherein the insulating particles are non-reducing oxides or nitrides. 7. A linear resistor characterized in that the insulating particles according to any one of claims 1 to 4 are alumina. 8. A linear resistor, wherein the flux component according to any one of claims 1 to 4 is at least one selected from non-reducing glass, feldspar, and aluminum silicate. 9. A gas circuit breaker including a breaker housed in a tank and a closing resistor, wherein the closing resistor has 4 to 40% by weight of metal boride, 20 to 50% by weight of clay and 30 to 30% by weight.
A gas circuit breaker comprising a sintered body containing 70% by weight of insulating particles and 0.1 to 10% by weight of a flux component. 10. A gas circuit breaker including a circuit breaker housed in a tank and a closing resistor, wherein the closing resistor is 4-40.
Wt% metal boride and 20-50 wt% clay and 30
A linear resistor composed of a sintered body containing ˜70% by weight of insulating particles and 0.1˜10% by weight of a flux component, and electrodes on opposite surfaces of the sintered body is used. A gas circuit breaker. 11. A neutral grounding resistor including a resistor housed in a tank, wherein the resistor comprises 4 to 40 wt% metal boride, 25 to 70 wt% clay and 1.0 to 55 wt%. % Of the insulating particles and 0.1 to 20% by weight of the sintered body containing the flux component, a neutral grounding resistor. 12. A neutral grounding resistor including a resistor housed in a tank, wherein the resistor comprises 4 to 40 wt% metal boride, 25 to 70 wt% clay and 1.0 to 55 wt%. % Of insulating particles and 0.1 to 20% by weight of a flux component, a linear resistor comprising a sintered body and electrodes on opposite surfaces of the sintered body is used. Point grounding resistor.