JP2001124816A - Insulator contamination detecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an insulator contamination detecting device for detecting the degree of contamination of an insulator without using a pilot insulator. SOLUTION: First and second voltage detecting electrodes 6 an 8 supported in a rack 3 for supporting an insulator 1 for supporting a high voltage electric wire, through an insulating supporting members 5, 7 and electrostatically combined to the insulator 1 are installed. The first voltage detecting electrode 6 is covered with an insulating layer 9 and the conductive part of the second voltage detecting electrode 6 is exposed. Voltage between the voltage detecting electrode 6 and earth, and voltage between the voltage detecting electrode 8 and earth are detected with capacitor potential dividing circuits 10, 11 to obtain a voltage detecting signals VS1, VS2. When the voltage detecting signal VS1 exceeds a criterion value and the voltage detecting signal VS2 becomes lower than the criterion value, a contamination judging device judges that the insulator 1 is contaminated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an insulator fouling detecting device for detecting a fouling state of an insulator used for supporting a conductor to which a high voltage is applied in a power plant, a substation, or the like.

[0002]

2. Description of the Related Art Insulators used to support conductors to which high voltage is applied in power plants and substations, etc., are deteriorated in withstand voltage performance when they are contaminated by salt carried by typhoons or seasonal winds. Cause a flashover,
This causes a ground fault. Therefore, when the insulator becomes in a heavy soiled state, it is necessary to clean the surface of the insulator to restore the dielectric strength of the insulator.

As a detecting device for detecting a soiled state of an insulator, a dew-point type insulator fouling detecting device, SB (Steam Bowl)
2. Description of the Related Art Insulator fouling detectors, APM (automatic cleaning type attached salt content measuring device) and the like are known.

The dew-point type insulator fouling detection device incorporates an electronic cooling element utilizing the Peltier effect in a pilot insulator having the same shape as an actual insulator, and cools the pilot insulator to a temperature lower than the dew point to collect moisture in the air. , Thereby forcibly moistening the contaminants adhering to the insulator,
This is a detection device for measuring the leakage resistance of the contaminated material.

The SB type insulator fouling detecting device is also a wet type in which the lower surface of the insulator cap is forcibly moistened by steam generated from an evaporating dish disposed below the cap of the pilot of the same shape as the actual insulator. This device measures the leakage resistance of the lower surface of a shino-kasa.

[0006] Further, APM is provided with a washing device for automatically washing a pilot insulator having the same shape as a fruit insulator and a device for collecting water used for washing, and measuring salt dissolved in the collected washing water. Is used to detect the degree of contamination.

[0007] In addition, there is known a method for measuring salt attached to an insulator by a rinsing method.

[0008]

As described above, the conventional dew-point type insulator fouling detection apparatus and the conventional SB type fouling type fouling detection apparatus use a pilot insulator of the same shape as a real insulator in order to detect the fouling state of the insulator. Since it is necessary to use the detection device, there has been a problem that the detection device becomes large in size and its cost increases.

In addition, in this type of conventional detection apparatus, since the pilot insulator is detected without detecting the contamination state of the fruit insulator directly, there is a problem that the detection of the contamination state is not reliable.

[0010] In an APM (automatic washing-type attached salt measuring apparatus), when a pilot insulator having the same shape as a real insulator is washed, water flowing down along the surface thereof is collected, and the salt dissolved in the collected water is measured. Therefore, the actual degree of contamination of the insulator can be measured equivalently. However,
In this measuring device, a measurement error occurs due to the effect of rain washing due to rainfall, and if the error accumulates, it becomes impossible to accurately detect a stained state. It is necessary to consider effects, accumulated errors, and the like, and there is a problem in that it is difficult to determine a stained state.

In addition, the method of washing with a lid requires manual work, so that much labor is required and there is a problem that the measurement is troublesome.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an insulator fouling detection apparatus capable of detecting that a pilot is fouled without using a pilot.

Another object of the present invention is to provide an insulator fouling detection device capable of detecting insulator fouling with high reliability without considering the accumulated error caused by the influence of rainfall.

Still another object of the present invention is to provide a simple structure,
An object of the present invention is to provide an insulator fouling detection device capable of detecting fouling of an insulator without incurring an increase in cost.

[0015]

SUMMARY OF THE INVENTION The present invention is directed to an insulator contamination detector which is fixed to a support at a ground potential portion and which is used to support a conductor to which a high voltage is applied. It concerns the device.

According to the present invention, there is provided a voltage detecting electrode which is supported by a ground potential portion via an insulating support member and is electrostatically coupled to the insulator via a floating capacitance; And a stain determination device for determining whether the insulator is soiled based on the magnitude of the voltage detection signal output from the voltage detection circuit. As the voltage detecting electrode, an electrode whose conductive portion is insulated is used. The contamination determination device is configured to determine that the insulator is dirty when the magnitude of the voltage detection signal exceeds a determination value.

When the insulator is contaminated, the impedance on the surface of the insulator decreases, and the electrostatic coupling between the voltage detecting electrode and the center conductor of the insulator increases. When the insulator is contaminated, the insulating support member is also contaminated, so the surface impedance is reduced.However, if the voltage detection electrode is insulated, the effect of the reduced impedance on the surface of the insulating support is reduced. Without receiving it, it is possible to faithfully detect that the electrostatic coupling between the voltage detection electrode and the center conductor of the insulator is strengthened. Therefore, the voltage detection signal obtained through the voltage detection electrode and the voltage detection circuit covered with the insulating coating has a characteristic of increasing as the degree of contamination of the insulator increases. Therefore, by providing an appropriate judgment value,
If it is determined that the insulator is contaminated when the magnitude of the voltage detection signal exceeds the determination value, it is possible to accurately detect that the insulator is contaminated.

In the present invention, as the voltage detecting electrode, an electrode whose conductive portion is exposed may be used. When the voltage detecting electrode with the conductive portion exposed is used, when the insulator and the insulating support member are contaminated and the surface impedance is lowered, the impedance between the voltage detecting electrode and the ground is several tens KΩ to several hundreds.
When the voltage drops to KΩ, a considerable part of the signal component detected through the voltage detection electrode flows to the ground circuit through the surface of the insulating support member. Therefore, due to the contamination of the insulator,
Even if the electrostatic coupling between the voltage detection electrode and the center conductor of the insulator becomes large, the voltage detection signal obtained through the voltage detection electrode and the voltage detection circuit becomes smaller than when there is no contamination of the insulator. .

At this time, the voltage detection signal has a characteristic that the voltage detection signal decreases as the degree of contamination of the insulator increases. Therefore, by setting a judgment value of an appropriate magnitude to the voltage detection signal and determining that the insulator is contaminated when the voltage detection signal is lower than the judgment value, the insulator is determined. Can be detected accurately.

According to the present invention, the first voltage detection device is supported by the ground potential portion via the first insulating support member, and the conductive portion is insulated and covered by the insulator via the floating capacitance. A second voltage detection electrode, which is supported on the ground potential portion via a second insulating support member and the conductive portion is exposed, and is electrically coupled to the insulator via a floating capacitance; A first voltage detection circuit for detecting a voltage between the first voltage detection electrode and the ground, a second voltage detection circuit for detecting a voltage between the second voltage detection electrode and the ground, and a first voltage A first voltage detection signal obtained from the detection circuit and a second voltage detection signal obtained from the second voltage detection circuit as inputs, and a fouling determination device for determining whether the insulator is fouled, Whether the magnitude of the first voltage detection signal exceeds the first determination value, The size of the second voltage detection signal and the second
It is preferable to determine that the insulator is soiled when it becomes smaller than the determination value of.

As described above, the voltage detected by the voltage detecting electrode having the conductive portion insulated and coated exceeds the judgment value, and the voltage detected by the voltage detecting electrode having the conductive portion exposed becomes lower than the judgment value. If it is determined that the insulator is contaminated when the insulator is contaminated, it is possible to judge that the insulator is contaminated by two voltage detection signals having different ways of changing the degree of contamination of the insulator. Can be more reliably determined.

According to the present invention, it is possible to detect the contamination of a fruit insulator without using a pilot, so that it is possible to reduce the size of the insulator contamination detection device and reduce the cost. In addition, since the pilot can directly detect the contamination of the insulator itself instead of detecting the contamination of the insulator, the reliability of detecting the contamination state of the insulator can be improved.

Also, without being affected by the rain washing effect,
Since the contamination state of the seedling can be detected, it is possible to easily determine whether or not the contamination is present.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an example of the configuration of an insulator fouling detecting apparatus according to the present invention. In FIG. 1, reference numeral 1 denotes an insulator for detecting the state of contamination by the contamination detection device according to the present invention, which is used for supporting the high-voltage wires 2 in a substation or the like. The illustrated insulator is a well-known line post having a structure in which a large number of caps 102, 102,... Arranged in the axial direction are protruded from the outer periphery of a solid cylindrical main body 101, and this insulator has a central axis. Are arranged in a state where they are oriented in the vertical direction, and a columnar neck lower portion 103 formed at the lower end thereof is fixed to a mount 3 at a ground potential, and the overhead wire 2 is connected to the upper end thereof. Reference numeral 4 denotes a power substation to which the overhead wire 2 is connected.

In the example shown in FIG. 1, near the lower end of the insulator 1, the insulator 1 is supported on the ground potential portion via the first insulating support member 5, and is electrostatically coupled to the insulator 1 via a floating capacitance. The first voltage detection electrode 6 and the second voltage electrostatically coupled to the insulator 1 via the floating capacitance by the insulator 1 supported by the ground potential portion via the second insulating support member 7. A detection electrode 8 is provided.

The first insulating support member 5 shown in FIG.
One end is fixed to one side surface of the upper part of the gantry 3, and the other end is formed of an L-shaped member directed upward. The first voltage detecting electrode 6 is formed of a plate made of a conductive material, and is disposed at a predetermined distance from the lower end of the insulator 1 to form an upper end of the first insulating support member 5. It is fixed to.

Similarly, the second insulating support member 7 is formed of an L-shaped member having one end fixed to the other side of the upper portion of the gantry 3 and the other end directed upward. The second voltage detection electrode 8 is made of a plate formed of a conductive material, and is separated from the lower end of the insulator 1 by a predetermined distance, like the first voltage detection electrode 6. It is arranged and fixed to the upper end of the second insulating support member 7.

The first and second insulating support members 5 and 7 may be formed of insulating resin, or may be formed of porcelain or the like.

As shown in FIG. 2, the first voltage detecting electrode 6 is completely covered with the insulating layer 9 and
The conductive portion of the voltage detecting electrode 6 is not exposed to the outside.

The second voltage detecting electrode 8 is provided without being covered with an insulating layer, with its conductive portion being exposed.

As shown in FIG. 2, the voltage between the first voltage detecting electrode 6 and the ground is changed to the first capacitor voltage dividing circuit 10.
And the voltage between the second voltage detecting electrode 8 and the ground is input to the second capacitor voltage dividing circuit 11.

The first capacitor voltage dividing circuit 10 is composed of an upper-stage capacitor C11 and a lower-stage capacitor C12 connected in series to the upper-stage capacitor and having a terminal opposite to the upper-stage capacitor C11 grounded. The voltage V1 between the first voltage detecting electrode 6 and the ground is applied to both ends of the series circuit of the capacitors C11 and C12.

The second capacitor voltage dividing circuit 11 is composed of an upper-stage capacitor C21 and a lower-stage capacitor C22 connected in series to the upper-stage capacitor and having a terminal opposite to the upper-stage capacitor C22 grounded. The voltage V2 between the second voltage detecting electrode 8 and the ground is applied to both ends of the series circuit of the capacitors C21 and C22.

The output voltage of the first capacitor voltage dividing circuit 10 obtained at both ends of the capacitor C12 is input to the contamination determination device 12 through the first amplifier A1, and the second capacitor voltage dividing circuit obtained at both ends of the capacitor C22. 11 is input to the contamination determination device 12 through the second amplifier A2.

In this example, the first capacitor voltage dividing circuit 1
0 and a first amplifier A1, a first voltage detecting circuit 1 for detecting a voltage V1 between the first voltage detecting electrode 6 and the ground.
3, the second capacitor voltage dividing circuit 11 and the second amplifier A2 constitute a second voltage detecting circuit 14 for detecting the voltage V2 between the second voltage detecting electrode 8 and the ground. I have.

The contamination determination device 12 receives the first voltage detection signal Vs1 obtained from the first voltage detection circuit 13 and the second voltage detection signal Vs2 obtained from the second voltage detection circuit as inputs, and makes the insulator dirty. Device to determine whether or not
This determination device is provided when the magnitude of the first voltage detection signal Vs1 exceeds the first determination value Vt1 and the magnitude of the second voltage detection signal Vs2 becomes smaller than the second determination value Vt2. It is determined that the insulator is soiled.

For example, as shown in FIG. 3, the above-described contamination determination device 12 can be configured to compare the first voltage detection signal Vs1 and the reference signal Vt1 for providing the determination value with the non-inverting input terminal and the inverting input terminal, respectively. The comparator CP1 receives a second voltage detection signal Vs2 and a reference signal Vt2 for providing a judgment value at an inverting input terminal and a non-inverting input terminal, respectively.
And an AND circuit AND1 that generates a judgment output indicating that the insulator is contaminated when the outputs of the comparators CP1 and CP2 both become high.

In the example of FIG. 3, when the first voltage detection signal Vs1 becomes larger than the reference signal Vt1, the output of the comparator CP1 becomes high, and the second voltage detection signal Vs2 becomes higher than the reference signal Vt2. When it becomes smaller, the output of the comparator CP2 becomes high. Therefore, the AND circuit AND1
Means that the magnitude of the first voltage detection signal Vs1 is equal to the first determination value V
t1 and the magnitude of the second voltage detection signal Vs2 is
When the value becomes smaller than the judgment value Vt2, a judgment output Vo indicating that the insulator is soiled is output.

In the above insulator fouling detection device, the first
As shown in FIG. 2, the voltage detecting electrode 6 and the second voltage detecting electrode 8 are electrostatically coupled to the insulator 1 through the floating capacitance Co, and furthermore, the insulator 1 is a dielectric material. It is electrostatically coupled to the inner center conductor. First
Between the voltage detection electrode 6 and the ground, the voltage between the center conductor of the insulator 1 and the ground, the capacitance between the center conductor and the first voltage detection electrode 6, and the first voltage detection A voltage V1 divided by the capacitance between the electrode for use and the ground appears. The capacitor voltage dividing circuit 13 divides this voltage V1 into capacitors C11 and C11.
12 to generate a voltage at both ends of the capacitor C12 in proportion to the ground potential of the center conductor of the insulator. The voltage at both ends of the capacitor C12 is amplified by the amplifier A1 and output as a first voltage detection signal Vs1.

Between the second voltage detecting electrode 8 and the ground, the voltage between the center conductor of the insulator 1 and the ground, and the capacitance between the center conductor and the second voltage detecting electrode 8 , A voltage V2 divided by the capacitance between the second voltage detecting electrode and the ground appears. The capacitor voltage dividing circuit 14 calculates the voltage V
2 is divided by capacitors C21 and C22 to generate a voltage proportional to the ground potential of the center conductor of the insulator 1 at both ends of the capacitor C22. The voltage across the capacitor C22 is amplified by the amplifier A2 and output as the second voltage detection signal Vs2.

If salt or the like adheres to the outer surface of the insulator 1 and the insulator 1 is contaminated, the impedance of the surface of the insulator 1 decreases, so that the first voltage detecting electrode 6 and the second voltage detecting electrode 8 The electrostatic coupling between the insulator and the center conductor of the insulator becomes stronger, and the voltage detected through the first voltage detecting electrode 6 and the second voltage detecting electrode 8 increases. When the insulator 1 is contaminated, the insulating support members 5 and 7 disposed near the insulator 1 are also contaminated, so that the surface impedance of each of the insulating support members 5 and 7 decreases to about several tens KΩ to several hundreds KΩ. .

Since the conductive portion of the first voltage detecting electrode 6 is completely covered with the insulating layer 9, when the insulator 1 is contaminated, the influence of the decrease in the surface impedance of the insulating supporting member 5 is obtained. Without being subjected to this, it is faithfully detected that the electrostatic coupling between the center conductor of the insulator 1 and the first voltage detecting electrode 6 has been strengthened, and the ground potential V1 is increased. Therefore, as shown in FIG. 4A, the first voltage detection signal Vs1 obtained from the first voltage detection circuit 13 has a characteristic that increases as the degree of contamination of the insulator increases. Therefore, the first voltage detection signal Vs1 is changed to an appropriate first voltage detection signal Vs1.
When the first voltage detection signal Vs1 exceeds the magnitude of the first reference signal Vt1, it can be determined that the insulator has been contaminated.

On the other hand, since the conductive portion of the second voltage detecting electrode 8 is exposed, when the surface impedance of the insulating support member 7 is reduced when the insulator 1 is contaminated, the second voltage is detected. A current flows from the detection electrode 8 through the surface of the insulating support member 7, and the voltage applied to the capacitor voltage dividing circuit 11 decreases. Therefore, even if the coupling between the second voltage detection electrode 8 and the center conductor of the insulator 1 becomes large due to the contamination of the insulator 1, the second voltage detection circuit 1
The voltage detection signal output through 4 becomes low.

Therefore, as shown in FIG. 4 (B), the voltage detection signal Vs2 obtained from the second voltage detection circuit 14 has a characteristic that it decreases as the degree of contamination of the insulator 1 increases. Therefore, the second voltage detection signal V
Comparing s2 with a second reference signal Vt2 that provides an appropriate second determination value, the insulator 1 is contaminated when the second voltage detection signal Vs2 becomes smaller than the second reference signal Vt2. A determination output can be obtained indicating that this is the case.

In this case, the impedance value of the upper stage capacitor C21 constituting the capacitor voltage dividing circuit 11 is
It is necessary to keep it at about several hundred KΩ at the commercial frequency.

In the example shown in FIG. 1, the voltage detection signal Vs1 obtained through the first voltage detection electrode 6 whose conductive portion is insulated and the voltage detection circuit 13 exceeds the first reference signal Vt1, and Second voltage detection electrode 8 and voltage detection circuit 14
When the voltage detection signal Vs2 obtained through the above becomes lower than the second reference signal Vt2, the insulator contamination judging device 12 outputs a judgment output Vo indicating that the insulator is contaminated.

The judgment output Vo can be used for operating a means for generating an alarm such as a lamp or a buzzer.

As described above, the first voltage detecting electrode 6 having the conductive portion insulated and the second voltage detecting electrode 8 having the conductive portion exposed are provided to form the first voltage detecting electrode 6. A first voltage detection signal Vs1 obtained through the electrode 6 and the voltage detection circuit 13 provides a first reference signal Vs giving an appropriate first determination value.
The voltage detection signal Vs2 exceeding t1 and obtained through the second voltage detection electrode 8 and the voltage detection circuit 14
When it is determined that the insulator is contaminated when the value becomes lower than the second reference signal Vt2 that gives the judgment value, it is possible to more reliably determine whether the insulator is contaminated.

However, the present invention is not necessarily limited to this, and the voltage detection signal Vs1 obtained through the first voltage detection electrode 6 whose conductive portion is insulated and the voltage detection circuit 13 is appropriate. When the reference signal Vt2 exceeds the reference signal Vt1 giving the judgment value, or the voltage detection signal Vs2 obtained through the second voltage detection electrode 8 and the voltage detection circuit 14 with the conductive portion exposed gives the reference signal Vt2 giving the appropriate judgment value.
A determination output indicating that the insulator has been contaminated when it becomes lower than the above may be obtained.

In the above example, the insulating support members 5 and 7 for supporting the first voltage detecting electrode 6 and the second voltage detecting electrode 8 on the gantry 3 (ground potential portion) are made of insulating resin. However, as shown in FIG. 5, insulators can be used as these insulating support members. In the example shown in FIG. 5, the arm members 15 and 16 are fixed to the upper part of the side surface of the gantry 3 by welding or the like, and the insulating support members 5 are attached to these arm members.
And 7 are attached respectively.

In the example shown in FIGS. 1 and 5, the first voltage detecting electrode 6 and the second voltage detecting electrode 8 are mounted with their respective plate surfaces oriented in the horizontal direction. For example, as shown in FIG. 6, the detection electrodes 6 and 8 may be attached in a state where the respective plate surfaces are inclined so as to be obliquely opposed to the insulator 1.

The mounting position of the voltage detecting electrode may be appropriately determined in consideration of the strength of electrostatic coupling (voltage detection sensitivity) between the electrode and the center conductor of the insulator and the constant of the voltage detecting circuit. .

[0053]

As described above, according to the present invention, it is possible to directly detect that a fruit insulator is contaminated without using a pilot insulator, so that it is possible to reduce the size of the insulator contamination detection device and reduce the cost. be able to.

In the present invention, since the pilot can directly detect the contamination of the insulator itself instead of detecting the contamination of the insulator, the reliability of detecting the contamination state of the insulator can be enhanced.

Further, according to the present invention, since the soiled state of the seedling can be detected without being affected by the rain washing effect, it is possible to easily determine the presence or absence of soiling.

In particular, according to the third aspect of the present invention, the manner of change with respect to the degree of contamination of the insulator differs.
Since it is determined that the insulator has been contaminated by the two voltage detection signals, it is possible to more reliably determine whether the insulator is contaminated.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a state in which a voltage detection electrode used in a contamination detection device according to the present invention is attached to an insulator.

FIG. 2 is a configuration diagram showing a main part of FIG. 1 and a configuration example of a voltage detection circuit connected to a voltage detection electrode.

FIG. 3 is a circuit diagram illustrating a configuration example of the contamination determination device illustrated in FIG. 2;

FIG. 4A shows a first example of the determination device shown in FIGS. 1 and 2;
FIG. 5 is a diagram showing an example of a relationship between a voltage detection signal obtained through a voltage detection electrode and a voltage detection circuit and a degree of contamination of an insulator. FIG. 3B is a diagram illustrating an example of a relationship between a voltage detection signal obtained through a second voltage detection electrode and a voltage detection circuit of the determination device illustrated in FIGS. 1 and 2 and an insulator contamination degree. .

FIG. 5 is a front view of a main part showing another configuration example near a voltage detection electrode used in the present invention.

FIG. 6 is a configuration diagram showing still another configuration example near a voltage detection electrode used in the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... insulator, 2 ... high voltage electric wire, 3 ... mount, 5 ... 1st insulating support member, 6 ... 1st voltage detection electrode, 7 ... 2nd insulating support member, 8 ... 2nd voltage detection electrode 10, a first capacitor voltage dividing circuit, 11: a second capacitor voltage dividing circuit,
12: Soil determination device, 13: First voltage detection circuit, 14
... A second voltage detection circuit.

Claims (3)

[Claims] 1. fixed to a support at a ground potential portion,
In an insulator fouling detection device for detecting the fouling of an insulator used to support a conductor to which a high voltage is applied, the insulator is supported by a ground potential section via an insulating support member, and is statically attached to the insulator via a floating capacitance. An electrically-coupled voltage detection electrode, a voltage detection circuit for detecting a voltage between the voltage detection electrode and ground, and the insulator being contaminated from the magnitude of the voltage detection signal output from the voltage detection circuit. The voltage detection electrode is provided with a conductive portion insulated and coated, and the contamination determination device is configured such that the magnitude of the voltage detection signal exceeds a determination value. An insulator fouling detection device, which is configured to determine that the insulator is fouled. 2. fixed to a support at a ground potential portion,
In an insulator fouling detection device for detecting the fouling of an insulator used to support a conductor to which a high voltage is applied, the insulator is supported by a ground potential section via an insulating support member, and is statically attached to the insulator via a floating capacitance. An electrically-coupled voltage detection electrode, a voltage detection circuit for detecting a voltage between the voltage detection electrode and ground, and the insulator being contaminated from the magnitude of the voltage detection signal output from the voltage detection circuit. The voltage detection electrode is provided in a state where the conductive portion is exposed, and the contamination determination device determines the magnitude of the voltage detection signal. An insulator fouling detection device configured to determine that the insulator is contaminated when the value becomes lower than the value. 3. fixed to a support at a ground potential portion,
An insulator fouling detection device for detecting fouling of an insulator used to support a conductor to which a high voltage is applied, comprising: a stray capacitance that is supported on a ground potential portion via a first insulating support member and that the stray capacitance is applied to the insulator. A first voltage detection electrode electrostatically coupled to the insulator via a second insulating support member at a ground potential portion and electrostatically coupled to the insulator via a floating capacitance; A second voltage detection electrode, a first voltage detection circuit for detecting a voltage between the first voltage detection electrode and ground, and a voltage between the second voltage detection electrode and ground. A second voltage detection circuit; and a first voltage detection signal obtained from the first voltage detection circuit and a second voltage detection signal obtained from the second voltage detection circuit as inputs. And a contamination determination device for determining whether or not The first voltage detection electrode is provided with its conductive portion insulated and covered, and the second voltage detection electrode is provided with its conductive portion exposed. When the magnitude of the detection signal exceeds a first determination value and the magnitude of the second voltage detection signal becomes smaller than a second determination value, it is determined that the insulator is contaminated. A garnish detector.