JPH11304871A - Insulator contamination detecting apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To grasp the meaning of the contaminated situation of an insulator at an early stage by constantly monitoring the contamination of the insulator by an insulator contamination detecting device of a simple constitution. SOLUTION: This insulator contamination detecting device is constituted of a detection current transformer for detecting a current flowing through an insulator 1, and a determination means 5 for detecting a partial discharge pulse current from a measured current by the detection current transformer, to determine that the insulator has been contaminated when the pulse current is detected. As insulation performance is deteriorated by contamination of the insulator 1, partial discharging is generated before a discharge current is generated. By detecting the pulse current by this partial discharging, the contamination of the inusulator 1 can be detected before the discharge current is generated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an apparatus for detecting contamination of an insulator.

[0002]

2. Description of the Related Art As insulator fouling progresses due to adhesion of salt and the like, the insulation performance of the insulator deteriorates, partial discharge occurs, and leakage current and discharge current sometimes flow. If this state is left unattended, dielectric breakdown may occur, leading to a serious accident. Conventionally, various methods have been proposed for measuring the pollution degree of insulators. Hereinafter, a typical method will be described.

As a usual method, there is a method using a pilot insulator. In this method, the pilot insulator is installed in the same environment as the actual insulator, and the pollution proceeds as much as the actual insulator. Then, the pilot insulator is manually immersed in fresh water and the amount of salt dissolved in the fresh water is measured to measure the amount of salt attached. As another method, there is a method using an antenna sensor. In this method, an antenna sensor detects an electromagnetic wave caused by partial discharge generated due to contamination of an actual device. Then, when a phenomenon peculiar to partial discharge is detected from the electromagnetic wave detected by the antenna sensor, it is determined that the insulator is contaminated.

There is also a method of measuring the leakage current of an actual machine by using a current transformer. As the contamination of the insulator progresses, the resistance value of the insulator surface decreases, and the leakage current increases. Therefore, when the leakage current measured by the current transformer exceeds a predetermined determination level, it is determined that the insulator is contaminated.

[0005]

The above-mentioned method using the pilot insulator consumes a great deal of time and money in equipment and labor. Further, this method cannot continuously monitor the degree of fouling. The method of detecting using an antenna sensor is as follows.
It is difficult to accurately detect partial discharge of the insulator due to the susceptibility to external noise and the spatial distance attenuation characteristics.

In the method of detecting a leakage current, a conventional current transformer has a poor detection sensitivity in a minute area, and cannot make an accurate determination. Leakage current flowing due to insulator contamination is
In the range of tens of microamps to several milliamps,
It is very small compared to the range of several milliamps to several tens or hundreds of milliamps of the discharge current flowing immediately before the flash. Since a normal current transformer has poor detection sensitivity in a minute current region, the leakage current cannot be measured accurately.

To measure a minute current, a current transformer with a built-in amplifier may be used. However, even in this case, since the electromagnetic noise in the space affects the signal line, the current in the minute current region is accurately measured. It is difficult. Furthermore, when the insulator is contaminated and a discharge current flows, there is a risk that the circuit may be damaged by surge energy at the time of discharge. In addition, since it is easily affected by spatial noise, it is necessary to use an expensive system that takes measures against the noise.

SUMMARY OF THE INVENTION It is an object of the present invention to constantly monitor insulator contamination by means of an insulator contamination detection device having a simple configuration, and to grasp the contamination status of the insulator at an early stage.

[0009]

In order to achieve the above object, the present invention provides a detecting current transformer for measuring a current flowing through an insulator, and detecting a minute pulse current due to a partial discharge from the measuring current of the detecting current transformer. Then, an insulator contamination detection device is constituted by the determination means for determining that the insulator is soiled when the pulse current is detected.

If the insulation performance of the insulator deteriorates with the progress of the contamination of the insulator, the combined leakage current of the capacitance component and the resistance component increases. A discharge current is involved. As shown in FIG. 4, generally, before this discharge current occurs, a minute partial discharge occurs near the voltage peak. When this partial discharge occurs, a minute pulse current of several μA to several mA due to the partial discharge flows superimposed on the leakage current. As the contamination further progresses, the pulse tends to increase and the number tends to increase. In the present invention, the current flowing through the insulator is constantly monitored by the detection current transformer, and when the partial discharge pulse current is detected, it is determined that the insulator is soiled, so that the status of the insulator being soiled is grasped at an early stage.

As described above, according to the present invention, a serious accident due to flashover can be prevented beforehand by detecting a pulse current due to partial discharge occurring before a discharge current is generated. In addition, since the current flowing through the detection current transformer can be always detected, it is possible to continuously monitor the status of contamination of the insulator. In addition, since the pulse current due to partial discharge is directly measured by the detection current transformer, external noise is less likely to be picked up as with an antenna sensor, and there is no measurement error due to the sensor installation position, so accurate measurement is possible. In addition, the contamination of the insulator can be detected.

Here, the judging means is an HPF (high-pass filter) for passing a signal of a high-frequency component from the output of the detection current transformer, and means for counting the number of pulses exceeding a predetermined judgment level among the outputs of the HPF. Can be provided. HPF cuts low frequency leakage current,
Only the partial discharge pulse current is taken out. The determining means determines that the insulator is soiled when the count value of the pulse current exceeds a predetermined threshold value. The HPF may be provided with L, C, etc. on the detection current transformer side as shown in FIG.

When a partial discharge occurs, a pulse current due to the partial discharge is continuously generated. Therefore, when the partial discharge pulse current is detected for a predetermined number or more within a predetermined time, it is determined that the insulator is soiled. On the other hand, transient noise is
It is rare that it is continuously detected by the detection current transformer. Therefore, erroneous determination due to transient noise can be prevented by setting the condition that the partial discharge pulse current is continuously detected a predetermined number of times or more.

According to the present invention, the detection current transformer can be connected to the determination means by an optical fiber, and the signal measured by the detection current transformer can be converted into an optical signal and transmitted to the determination means. In this case, the optical fiber does not pick up electromagnetic waves of external noise, so that the influence of external noise can be further eliminated.

[0015]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a circuit configuration diagram of an insulator fouling detection device,
FIG. 2 is a circuit configuration diagram of the detection current transformer used in the apparatus of FIG. In order to measure a current flowing through the insulator 1 for which contamination is to be detected, the detection current transformer 3 is connected to a ground wire 7 that grounds the mounting base 2 of the insulator 1. The current value measured by the detection current transformer 3 is converted into an optical signal and transmitted to the determination unit 5 by the optical fiber 4. Further, sensors 6 such as a temperature sensor and a humidity sensor are connected to the determination unit 5.

The configuration of the detection current transformer 3 will be described with reference to FIG. The primary winding 12 is formed by winding the ground wire 7 around the current transformer core 11 a plurality of times. The transmission LED 14 is connected to the secondary winding 13, and the LED 14 converts an electric signal flowing through the secondary winding 12 into an optical signal. This light is transmitted to the determination unit 5 by the optical fiber 4 of FIG.

The LED 14 has a non-linear resistance characteristic,
Shows high resistance to small currents. With the detection current transformer 3
Can be reduced by applying a bias current to the LED 14.
It is assumed that the resistance value in the current region is small. DC bike
The ass power supply 15 has a resistor R₁, R _TwoTo LED 14 via
Supply bias current. High voltage is induced in the secondary winding 13
In order to protect the LED 14 when it is
The protection elements 16 are connected in parallel. DC to secondary winding 13
To prevent current from flowing in and saturating the iron core,
A capacitor is connected between the DC bias power supply 15 and the secondary winding 13.
Are connected in series.

From the high voltage induced in the secondary winding 13, LE
To further protect D14, protection diode 17
It is connected in series with the polarity opposite to that of the LED 14 between the next winding 13 and the LED 14. A bias current flows from the DC bias power supply 15 through the resistors R ₁ and R ₃ and the bias diode D so that a minute current measured by the secondary winding 13 can flow through the protection diode 17.

In the example of FIG. 2, the primary winding 13 has a plurality of turns in order to increase the apparent current and facilitate detection, but as shown in FIG. Through the iron core 11 to make only one turn.
Returning to FIG. 1, the current value measured by the detection current transformer 3 is converted into an optical signal and transmitted to the determination unit 5 through the optical fiber 4. Here, in the optical fiber 4, since the current is not induced by the electromagnetic wave of the external noise, the influence of the external noise is eliminated. For this reason, the distance between the detection current transformer 3 and the determination unit 5 can be increased. If there is no possibility that external noise will be picked up during transmission, the detection current transformer 3 may be constituted by a normal current transformer, and the LED 14 and the like may be omitted.

Here, the configuration of the determination unit 5 will be described. The determination unit 5 includes a CPU 21, and a counter 22, an A / D converter 23, a memory 24, and an input / output interface 25 are connected to the CPU 21 via a bus. A display 26, a printer 27, and an operation panel 28 are further connected to the input / output interface 25. Further, a contact output 29 and an analog output 30 are output from the input / output interface 25. The contact output 29 turns on or off the contact by operating the relay Ry when the insulator contamination is detected.

The optical signal transmitted by the optical fiber 4 is
The optical / electrical converter 31 converts the electric signal into an electric signal. The electric signal is amplified by the preamplifier 32, and only the high frequency component is extracted by the HPF 33. As a result, the low-frequency leakage current component is cut, and a pulse current due to the high-frequency partial discharge is extracted. This partial discharge pulse current is detected by a detector 34 and input to a PH conversion circuit (peak hold conversion circuit) 35.

When a partial discharge pulse current whose peak value exceeds the determination level is detected, the PH conversion circuit 35 converts the waveform into a waveform and outputs it. The counter 22 counts the number of the output signals. As a result, the number of pulses generated by the partial discharge is counted by the counter 22. Further, the counter 22 is reset so that the count value becomes zero.

The signal detected by the sensor 6 is input to the A / D converter 23 through the signal conversion circuit 36 and is converted into a digital signal. Judgment of insulator contamination is C
In the PU 21, the processing is performed according to the program stored in the memory 24. The CPU 21 determines the presence or absence of the partial discharge, that is, the presence or absence of the insulator based on the count value of the counter 22.

Next, the determination operation of the CPU 21 will be described. At every predetermined interval time, the counter 2
The count value of 2 is read, and it is determined whether the count value has exceeded a predetermined threshold. Here, when the insulator 1 is not contaminated or light, the output of the PH conversion circuit 35 is 0 because no partial discharge occurs. Therefore,
Since the count value of the counter 22 is also 0, it is determined that the insulator is not soiled.

Even if the insulator 1 is not contaminated, the PH conversion circuit 35 may output due to accidental external noise, and the counter 22 may count.
In the case of this accidental external noise, it is rare that the noise is continuously counted. Therefore, the count value does not exceed the threshold value, and it is determined that the insulator is not stained. As described above, the provision of the counter 22 can prevent malfunction due to external noise.

When this determination is completed, the count value of the counter 22 is reset and the elapse of the set interval time is waited. The counter 22 counts the signal output from the PH conversion circuit 35 until the next set interval time elapses. After the elapse of the set interval time, the above determination operation is performed again. When the insulator 1 becomes more contaminated, partial discharge occurs prior to generation of a discharge current. When a partial discharge occurs, a pulse due to the partial discharge is continuously generated, so that the PH conversion circuit 35 continuously outputs a signal to the counter 22. Therefore, when the value counted by the counter 22 exceeds the threshold value during the set interval time, it is determined that the insulator is soiled.

The judging section 5 displays on the display 26 that the insulator has been contaminated, prints out by the printer 27, and switches the contact output 29. Then, the counter value of the counter 22 is reset. Cleaning of insulators and other necessary measures are taken based on these indications. According to the embodiment of the present invention described above, it is possible to reliably detect a partial discharge that occurs prior to a discharge current.
Insulator fouling can be detected before a serious accident occurs. When salt damage or the like progresses, the leakage current accompanies the discharge current. However, when the surrounding humidity is low, the discharge current may not be generated even if the contamination progresses. In such a case, if a typhoon approaches and the humidity rises,
There is a risk of rapid contamination and flashover at the same time as the generation of discharge current. However, since the partial discharge generally occurs before the phenomenon of the discharge current of the leakage current appears, an accident due to rapid pollution of the situation can be prevented.

The determination level used to determine the presence or absence of the partial discharge pulse current is adjusted according to the temperature and humidity detected by the sensor 6 such as a temperature sensor or a humidity sensor, or the threshold value of the counter 22 is counted. By adjusting the value, more detailed judgment can be made. In addition,
In the present invention, as shown in FIG. 5, an HPF including L and C may be provided in the detection current transformer 3. In this case, the detection current transformer 3 optically converts only the pulse current and outputs it.

[Brief description of the drawings]

FIG. 1 is a diagram showing a circuit configuration of an insulator fouling detection device to which the present invention is applied.

FIG. 2 is a diagram showing a configuration of a detection current transformer in FIG.

FIG. 3 is a diagram showing a modified example of the detection current transformer of FIG. 2;

FIG. 4 is a diagram showing a pulse current due to partial discharge.

FIG. 5 is a view showing a modification of FIG. 2;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Insulator 2 ... Insulator base 3 ... Detection current transformer 4 ... Optical fiber 5 ... Judgment part 6 ... Sensor 7 ... Ground wire 11 ... Iron core 12 ... Primary winding 13 ... Secondary winding 14 ... LED 15 ... DC Bias power supply 16 ... Protection element 17 ... Protection diode 21 ... CPU 22 ... Counter 23 ... A / D converter 24 ... Memory 25 ... Display 27 ... Printer 28 ... Operation panel 29 ... Contact output 30 ... Analog output R ... Resistance C ... Capacity D: Diode

Claims (4)

[Claims] 1. A current transformer for measuring a current flowing through an insulator, a pulse current due to partial discharge is detected from a current measured by the current transformer, and the insulator is contaminated when the pulse current is detected. And a determination means for determining whether or not the insulator is dirty. 2. A high-pass filter that passes a signal of a high-frequency component from an output of the detection current transformer, and a unit that counts the number of pulses exceeding a predetermined determination level in the output of the high-pass filter. The insulator contamination detecting device according to claim 1, further comprising: determining that the insulator is soiled when the count value exceeds a predetermined threshold value. 3. The current transformer, a current transformer, an LED that converts an output signal of the current transformer into an optical signal, and the LED.
And a means for supplying a DC bias current to the determination means, and the optical signal is transmitted to the determination means by an optical fiber.
Or the insulator fouling detection device according to 2. 4. The insulator fouling detection device according to claim 3, wherein the high-pass filter is provided in the detection current transformer, and the detection current transformer converts only a pulse current into an optical signal.